material. Among these are _Anthidium septemdentatum_ and _A. bellicosum_.
The former species chooses an old snail-shell as its nidus, and constructs
in it near the top a barrier of resin, so as to shut off the part where the
whorl is too small; then beneath the shelter of this barrier it accumulates
a store of honey-pollen, deposits an egg, and completes the cell by another
transverse barrier of resin; two such cells are usually constructed in one
snail-shell, and below them is placed a barricade of small miscellaneous
articles, similar to what we have described in speaking of the
cotton-working species of the genus. This bee completes its metamorphosis,
and is ready to leave the cell in early spring. Its congener, _A.
bellicosum_, has the same habits, with the exception that it works later in
the year, and is thus exposed to a great danger, that very frequently
proves fatal to it. This bee does not completely occupy the snail-shell
with its cells, but leaves the lower and larger portion of the shell
vacant. Now, there is another bee, a species of _Osmia_, that is also fond
of snail-shells as a nesting-place, and that affects the same localities as
the _A. septemdentatum_; very often the _Osmia_ selects for its nest the
vacant part of a shell, the other part of which is occupied by the
_Anthidium_; the result of this is that when the metamorphoses are
completed, the latter bee is unable to effect its escape, and {48}thus
perishes in the cell. Fabre further states with regard to these interesting
bees, that no structural differences of the feet or mandibles can be
detected between the workers in cotton and the workers in resin; and he
also says that in the case where two cells are constructed in one
snail-shell, a male individual is produced from the cell of the greater
capacity, and a female from the other.
_Osmia_ is one of the most important of the genera of bees found in Europe,
and is remarkable for the diversity of instinct displayed in the formation
of the nests of the various species. As a rule they avail themselves for
nidification of hollow places already existing; choosing excavations in
wood, in the mortar of walls, and even in sandbanks; in several cases the
same species is found to be able to adapt itself to more than one kind of
these very different substances. This variety of habit will render it
impossible for us to do justice to this interesting genus within the space
at our disposal, and we must content ourselves with a consideration of one
or two of the more instructive of the traits of _Osmia_ life. _O.
tridentata_ forms its nest in the stems of brambles, of which it excavates
the pith; its mode of working and some other details of its life have been
well depicted by Fabre. The Insect having selected a suitable bramble-stalk
with a cut extremity, forms a cylindrical burrow in the pith thereof,
extending the tunnel as far as will be required to allow the construction
of ten or more cells placed one after the other in the axis of the
cylinder; the bee does not at first clear out quite all the pith, but
merely forms a tunnel through it, and then commences the construction of
the first cell, which is placed at the end of the tunnel that is most
remote from the entrance. This cavity is to be of oval form, and the Insect
therefore cuts away more of the pith so as to make an oval space, but
somewhat truncate, as it were, at each end, the plane of truncation at the
proximal extremity being of course an orifice.
[Illustration: Fig. 21.—_Osmia tricornis_, ♀. Algeria.]
{49}The first cell thus made is stored with pollen and honey, and an egg is
deposited. Then a barrier has to be constructed to close this chamber; the
material used for the barrier is the pith of the stem, and the Insect cuts
the material required for the purpose from the walls of the second chamber;
the excavation of the second chamber is, in fact, made to furnish the
material for closing up the first cell. In this way a chain of cells is
constructed, their number being sometimes as many as fifteen. The mode in
which the bees, when the transformations of the larvae and pupae have been
completed, escape from the chain of cells, has been the subject of much
discussion, and errors have arisen from inference being allowed to take the
place of observation. Thus Dufour, who noted this same mode of construction
and arrangement in another Hymenopteron (_Odynerus nidulator_), perceived
that there was only one orifice of exit, and also that the Insect that was
placed at the greatest distance from this was the one that, being the
oldest of the series, might be expected to be the first ready to emerge;
and as the other cocoons would necessarily be in the way of its getting
out, he concluded that the egg that was last laid produced the first Insect
ready for emergence. Fabre tested this by some ingenious experiments, and
found that this was not the case, but that the Insects became ready to
leave their place of imprisonment without any reference to the order in
which the eggs were laid, and he further noticed some very curious facts
with reference to the mode of emergence of _Osmia tridentata_. Each Insect,
when it desires to leave the bramble stem, tears open the cocoon in which
it is enclosed, and also bites through the barrier placed by the mother
between it and the Insect that is next it, and that separates it from the
orifice of exit. Of course, if it happen to be the outside one of the
series it can then escape at once; but if it should be one farther down in
the Indian file it will not touch the cocoon beyond, but waits patiently,
possibly for days; if it then still find itself confined it endeavours to
escape by squeezing past the cocoon that intervenes between it and liberty,
and by biting away the material at the sides so as to enlarge the passage;
it may succeed in doing this, and so get out, but if it fail to make a side
passage it will not touch the cocoons that are in its way. In the ordinary
course of events, supposing all to go well with the family, all the cocoons
produce their inmates in a state for emergence within {50}a week or two,
and so all get out. Frequently, however, the emergence is prevented by
something having gone wrong with one of the outer Insects, in which case
all beyond it perish unless they are strong enough to bite a hole through
the sides of the bramble-stem. Thus it appears that whether a particular
_Osmia_ shall be able to emerge or not depends on two things—(1) whether
all goes well with all the other Insects between it and the orifice, and
(2) whether the Insect can bite a lateral hole or not; this latter point
also largely depends on the thickness of the outer part of the stem of the
bramble. Fabre's experiments on these points have been repeated, and his
results confirmed by Nicolas.
The fact that an _Osmia_ would itself perish rather than attack the cocoon
of its brother or sister is certainly very remarkable, and it induced Fabre
to make some further experiments. He took some cocoons containing dead
specimens of _Osmia_, and placed them in the road of an _Osmia_ ready for
exit, and found that in such case the bee made its way out by demolishing
without any scruple the cocoons and dead larvae that intervened between it
and liberty. He then took some other reeds, and blocked the way of exit
with cocoons containing living larvae, but of another species of
Hymenoptera. _Solenius vagus_ and _Osmia detrita_ were the species
experimented on in this case, and he found that the _Osmia_ destroyed the
cocoon and living larvae of the _Solenius_, and so made its way out. Thus
it appears that _Osmia_ will respect the life of its own species, and die
rather than destroy it, but has no similar respect for the life of another
species.
Some of Fabre's most instructive chapters are devoted to the habits and
instincts of various species of the genus _Osmia_. It is impossible here to
find space even to summarise them, still more impossible to do them
justice; but we have selected the history just recounted, because it is
rare to find in the insect world instances of such self-sacrifice by an
individual for one of the same generation. It would be quite improper to
generalise from this case, however, and conclude that such respect for its
own species is common even amongst the Osmia. Fabre, indeed, relates a case
that offers a sad contrast to the scene of self-sacrifice and respect for
the rights of others that we have roughly portrayed. He was able to induce
a colony of _Osmia tricornis_ (another species of the genus, be it noted)
to establish itself and {51}work in a series of glass tubes that he placed
on a table in his laboratory. He marked various individuals, so that he was
able to recognise them and note the progress of their industrial works.
Quite a large number of specimens thus established themselves and concluded
their work before his very eyes. Some individuals, however, when they had
completed the formation of a series of cells in a glass tube or in a reed,
had still not entirely completed their tale of work. It would be supposed
that in such a case the individual would commence the formation of another
series of cells in an unoccupied tube. This was not, however, the case. The
bee preferred tearing open one or more cells already completed—in some
cases, even by itself—scattering the contents, and devouring the egg; then
again provisioning the cell, it would deposit a fresh egg, and close the
chamber. These brief remarks will perhaps suffice to give some idea of the
variety of instinct and habit that prevails in this very interesting genus.
Friese observes that the variety of habits in this genus is accompanied as
a rule by paucity of individuals of a species, so that in central Europe a
collector must be prepared to give some twenty years or so of attention to
the genus before he can consider he has obtained all the species of _Osmia_
that inhabit his district.
As a prelude to the remarks we are about to make on the leaf-cutting bees
of the genus _Megachile_ it is well to state that the bee, the habits of
which were described by Réaumur under the name of "l'abeille tapissière,"
and that uses portions of the leaves of the scarlet poppy to line its nest,
is now assigned to the genus _Osmia_, although Latreille, in the interval
that has elapsed since the publication of Réaumur's work, founded the genus
_Anthocopa_ for the bee in question. _Megachile_ is one of the most
important of the genera of the Dasygastres, being found in most parts of
the world, even in the Sandwich Islands; it consists of bees averaging
about the size of the honey-bee (though some are considerably larger,
others smaller), and having the labrum largely developed; this organ is
capable of complete inflection to the under side of the head, and when in
the condition of repose it is thus infolded, it underlaps and protects the
larger part of the lower lip; the mandibles close over the infolded labrum,
so that, when the Insect is at rest, this appears to be altogether absent.
These bees are called leaf-cutters, from their habit of forming the cells
for their nest {52}out of pieces of the leaves of plants. We have several
species in Britain; they are very like the common honey-bee in general
appearance, though rather more robustly formed. These Insects, like the
Osmiae, avail themselves of existing hollow places as receptacles in which
to place their nests. _M. albocincta_ frequently takes possession of a
deserted worm-burrow in the ground. The burrow being longer than necessary
the bee commences by cutting off the more distant part by means of a
barricade of foliage; this being done, it proceeds to form a series of
cells, each shaped like a thimble with a lid at the open end (Fig. 22, A).
The body of the thimble is formed of large oval pieces of leaf, the lid of
smaller round pieces; the fragments are cut with great skill from the
leaves of growing plants by the Insect, which seems to have an idea of the
form and size of the piece of foliage necessary for each particular stage
of its work.
[Illustration: Fig. 22—Nidification of leaf-cutting bee, _Megachile
anthracina_. A, one cell separated, with lid open; the larva (_a_) reposing
on the food; B, part of a string of the cells. (After Horne.)]
Horne has given particulars as to the nest of _Megachile anthracina_
(_fasciculata_), an East Indian species.[30] The material employed was
either the leaves of the Indian pulse or of the rose. Long pieces are cut
by the Insect from the leaf, and with these a cell is formed; a circular
piece is next cut, and with this a lid is made for the receptacle. The
cells are about the size and shape of a common thimble; in one specimen
that Horne examined no less than thirty-two pieces of leaf disposed in
seven layers were used for one cell, in addition to three pieces for the
round top. The cells are carefully prepared, and some kind of matter of a
gummy nature is believed to be used to keep in place the pieces forming the
interior layers. The cells are placed end to end, as shown in Fig. 22, B;
five to seven cells form a series, and four or six series are believed to
be constructed by one pair {53}of this bee, the mass being located in a
hollow in masonry or some similar position. Each cell when completed is
half filled with pollen in the usual manner, and an egg is then laid in it.
This bee is much infested by parasites, and is eaten by the Grey Hornbill
(_Meniceros bicornis_).
_Megachile lanata_ is one of the Hymenoptera that in East India enter
houses to build their own habitations. According to Horne both sexes take
part in the work of construction, and the spots chosen are frequently of a
very odd nature. The material used is some kind of clay, and the natural
situation may be considered to be the interior of a hollow tube, such as
the stem of a bamboo; but the barrel of a gun, and the hollow in the back
of a book that has been left lying open, have been occasionally selected by
the Insect as suitable. Smith states that the individuals developed in the
lower part of a tubular series of this species were females, "which sex
takes longer to develop, and thus an exit is not required for them so soon
as for the occupants of the upper cells which are males." _M. proxima_, a
species almost exactly similar in appearance to _M. lanata_, makes its
cells of leaf-cuttings, however, and places them in soft soil.
Fabre states that _M. albocincta_, which commences the formation of its
nest in a worm-burrow by means of a barricade, frequently makes the
barricade, but no nest; sometimes it will indeed make the barricade more
than twice the proper size, and thus completely fill up the worm burrow.
Fabre considers that these eccentric proceedings are due to individuals
that have already formed proper nests elsewhere, and that after completing
these have still some strength remaining, which they use up in this
fruitless manner.
The SOCIAL BEES (Sociales) include, so far as is yet known, only a very
small number of genera, and are so diverse, both in habits and structure,
that the propriety of associating them in one group is more than doubtful;
the genera are _Bombus_ (Fig. 331, vol. v.), with its commensal genus or
section, _Psithyrus_ (Fig. 23); _Melipona_ (Fig. 24), in which _Trigona_
and _Tetragona_ may at present be included, and _Apis_ (Fig. 6); this
latter genus comprising the various honey-bees that are more or less
completely domesticated in different parts of the world.
In the genus _Bombus_ the phenomena connected with the social life are more
similar to what we find among wasps {54}than to what they are in the genus
_Apis_. The societies come to an end at the close of the season, a few
females live through the winter, and each of these starts a new colony in
the following spring. Males, females and workers exist, but the latter are
not distinguished by any good characters from the females, and are, in
fact, nothing but more or less imperfect forms thereof; whereas in _Apis_
the workers are distinguished by structural characters not found in either
of the true sexes.
Hoffer has given a description of the commencement of a society of _Bombus
lapidarius_.[31] A large female, at the end of May, collected together a
small mass of moss, then made an expedition and returned laden with pollen;
under cover of the moss a cell was formed of wax taken from the hind-body
and mixed with the pollen the bee had brought in; this cell was fastened to
a piece of wood; when completed it formed a subspherical receptacle, the
outer wall of which consisted of wax, and whose interior was lined with
honey-saturated pollen; then several eggs were laid in this receptacle, and
it was entirely closed. Hoffer took the completed cell away to use it for
museum purposes, and the following day the poor bee that had formed it
died. From observations made on _Bombus agrorum_ he was able to describe
the subsequent operations; these are somewhat as follows:—The first cell
being constructed, stored, and closed, the industrious architect, clinging
to the cell, takes a few days' rest, and after this interval commences the
formation of a second cell; this is placed by the side of the first, to
which it is connected by a mixture of wax and pollen; the second cell being
completed a third may be formed; but the labours of the constructor about
this time are augmented by the hatching of the eggs deposited a few days
previously; for the young larvae, having soon disposed of the small
quantity of food in the interior of the waxen cell, require feeding. This
operation is carried on by forming a small opening in the upper part of the
cell, through which the bee conveys food to the interior by ejecting it
from her mouth through the hole; whether the food is conveyed directly to
the mouths of the larvae or not, Hoffer was unable to observe; it being
much more difficult to approach this royal founder without disturbing her
than it is the worker-bees that carry on similar occupations at a
subsequent period in the history of the {55}society. The larvae in the
first cell, as they increase in size, apparently distend the cell in an
irregular manner, so that it becomes a knobbed and rugged, truffle-like
mass. The same thing happens with the other cells formed by the queen. Each
of these larval masses contains, it should be noticed, sister-larvae all of
one age; when full grown they pupate in the mass, and it is worthy of
remark that although all the eggs in one larval mass were laid at the same
time, yet the larvae do not all pupate simultaneously, neither do all the
perfect Insects appear at once, even if all are of one sex. The pupation
takes place in a cocoon that each larva forms for itself of excessively
fine silk. The first broods hatched are formed chiefly, if not entirely, of
workers, but small females may be produced before the end of the season.
Huber and Schmiedeknecht state that though the queen provides the
worker-cells with food before the eggs are placed therein, yet no food is
put in the cells in which males and females are produced. The queen, at the
time of pupation of the larvae, scrapes away the wax by which the cocoons
are covered, thus facilitating the escape of the perfect Insect, and, it
may also be, aiding the access of air to the pupa. The colony at first
grows very slowly, as the queen can, unaided, feed only a small number of
larvae. But after she receives the assistance of the first batch of workers
much more rapid progress is made, the queen greatly restricting her
labours, and occupying herself with the laying of eggs; a process that now
proceeds more and more rapidly, the queen in some cases scarcely ever
leaving the nest, and in others even becoming incapable of flight. The
females produced during the intermediate period of the colony are smaller
than the mother, but supplement her in the process of egg-laying, as also
do the workers to a greater or less extent. The conditions that determine
the egg-laying powers of these small females and workers are apparently
unknown, but it is ascertained that these powers vary greatly in different
cases, so that if the true queen die the continuation of the colony is
sometimes effectively carried on by these her former subordinates. In other
cases, however, the reverse happens, and none of the inhabitants may be
capable of producing eggs: in this event two conditions may be present;
either larvae may exist in the nest, or they may be absent. In the former
case the workers provide them with food, and the {56}colony may thus still
be continued; but in the latter case, there being no profitable occupation
for the bees to follow, they spend the greater part of the time sitting at
home in the nest.
Supposing all to go well with the colony it increases very greatly, but its
prosperity is checked in the autumn; at this period large numbers of males
are produced as well as new queens, and thereafter the colony comes to an
end, only a few fertilised females surviving the winter, each one to
commence for herself a new colony in the ensuing spring.
The interior of the nest of a bumble-bee (_Bombus_) frequently presents a
very irregular appearance; this is largely owing to the fact that these
bees do not use the cells as cradles twice, but form others as they may be
required, on the old remains. The cells, moreover, are of different sizes,
those that produce workers being the smallest, those that cradle females
being the largest, while those in which males are reared are intermediate
in size. Although the old cells are not used a second time for rearing
brood they are nevertheless frequently adapted to the purposes of
receptacles for pollen and for honey, and for these objects they may be
increased in size and altered in form.
It may be gathered from various records that the period required to
complete the development of the individual _Bombus_ about midsummer is four
weeks from the deposition of the egg to the emergence of the perfect
Insect, but exact details and information as to whether this period varies
with the sex of the Insect developed are not to be found. The records do
not afford any reason for supposing that such distinction will be found to
exist: the size of the cells appears the only correlation, suggested by the
facts yet known, between the sex of the individual and the circumstances of
development.
The colonies of _Bombus_ vary greatly in prosperity, if we take as the test
of this the number of individuals produced in a colony. They never,
however, attain anything at all approaching to the vast number of
individuals that compose a large colony of wasps, or that exist in the
crowded societies of the more perfectly social bees. A populous colony of a
subterranean _Bombus_ may attain the number of 300 or 400 individuals.
Those that dwell on the surface are as a rule much less populous, as they
are less protected, so that changes of weather are more {57}prejudicial to
them. According to Smith, the average number of a colony of _B. muscorum_
in the autumn in this country is about 120—viz. 25 females, 36 males, 59
workers. No mode of increasing the nests in a systematic manner exists in
this genus; they do not place the cells in stories as the wasps do; and
this is the case notwithstanding the fact that a cell is not twice used for
the rearing of young. When the ground-space available for cell-building is
filled the _Bombus_ begins another series of cells on the ruins of the
first one. From this reason old nests have a very irregular appearance, and
this condition of seeming disorder is greatly increased by the very
different sizes of the cells themselves. We have already alluded to some of
these cells, more particularly to those of different capacities to suit the
sexes of the individuals to be reared in them. In addition to these there
are honey-tubs, pollen-tubs, and the cells of the _Psithyrus_ (Fig. 23),
the parasitic but friendly inmates of the _Bombus_-nests. A nest of
_Bombus_, exhibiting the various pots projecting from the remains of empty
and partially destroyed cells, presents, as may well be imagined, a very
curious appearance. Some of the old cells apparently are partly destroyed
for the sake of the material they are composed of. Others are formed into
honey-tubs, of a make-shift nature. It must be recollected that, as a
colony increases, stores of provisions become absolutely necessary,
otherwise in bad weather the larvae could not be fed. In good weather, and
when flowers abound, these bees collect and store honey in abundance; in
addition to placing it in the empty pupa-cells, they also form for it
special receptacles; these are delicate cells made entirely of wax filled
with honey, and are always left open for the benefit of the community. The
existence of these honey-tubs in bumble-bees' nests has become known to our
country urchins, whose love for honey and for the sport of bee-baiting
leads to wholesale destruction of the nests. According to Hoffer, special
tubs for the storing of pollen are sometimes formed; these are much taller
than the other cells. The _Psithyrus_ that live in the nests with the
_Bombus_ are generally somewhat larger than the latter, and consequently
their cells may be distinguished in the nests by their larger size. A
bumble-bees' nest, composed of all these heterogenous chambers rising out
of the ruins of former layers of cells, presents a scene of such apparent
disorder that {58}many have declared that the bumble-bees do not know how
to build.
Although the species of _Bombus_ are not comparable with the hive-bee in
respect of the perfection and intelligent nature of their work, yet they
are very industrious Insects, and the construction of the dwelling-places
of the subterranean species is said to be carried out in some cases with
considerable skill, a dome of wax being formed as a sort of roof over the
brood cells. Some work even at night. Fea has recorded the capture of a
species in Upper Burmah working by moonlight, and the same industry may be
observed in this country if there be sufficient heat as well as light.
Godart, about 200 years ago, stated that a trumpeter-bee is kept in some
nests to rouse the denizens to work in the morning: this has been treated
as a fable by subsequent writers, but is confirmed in a circumstantial
manner by Hoffer, who observed the performance in a nest of _B. ruderatus_
in his laboratory. On the trumpeter being taken away its office was the
following morning filled by another individual The trumpeting was done as
early as three or four o'clock in the morning, and it is by no means
impossible that the earliness of the hour may have had something to do with
the fact that for 200 years no one confirmed the old naturalist's
observation.
One of the most curious facts in connection with _Bombus_ is the excessive
variation that many of the species display in the colour of the beautiful
hair with which they are so abundantly provided. There is not only usually
a difference between the sexes in this respect, but also extreme variation
within the limits of the same sex, more especially in the case of the males
and workers; there is also an astonishing difference in the size of
individuals. These variations are carried to such an extent that it is
almost impossible to discriminate all the varieties of a species by
inspection of the superficial characters. The structures peculiar to the
male, as well as the sting of the female, enable the species to be
determined with tolerable certainty. Cholodkovsky,[32] on whose authority
this statement as to the sting is made, has not examined it in the workers,
so that we do not know whether it is as invariable in them as he states it
to be in queens of the same species. According to Handlirsch,[33] each
{59}species of _Bombus_ has the capacity of variation, and many of the
varieties are found in one nest, that is, among the offspring of a single
pair of the species, but many of the variations are restricted to certain
localities. Some of the forms can be considered as actual ("fertige")
species, intermediate forms not being found, and even the characters by
which species are recognised being somewhat modified. As examples of this
he mentions _Bombus silvarum_ and _B. arenicola_, _B. pratorum_ and _B.
scrimshiranus_. In other cases, however, the varieties are not so
discontinuous, intermediate forms being numerous; this condition is more
common than the one we have previously described; _B. terrestris_, _B.
hortorum_, _B. lapidarius_ and _B. pomorum_ are examples of these variable
species. The variation runs to a considerable extent in parallel lines in
the different species, there being a dark and a light form of each; also
each species that has a white termination to the body appears in a form
with a red termination, and _vice versa_. In the Caucasus many species that
have everywhere else yellow bands possess them white; and in Corsica there
are species that are entirely black, with a red termination to the body,
though in continental Europe the same species exhibit yellow bands and a
white termination to the body. With so much variation it will be readily
believed that much remains to be done in the study of this fascinating
genus. It is rich in species in the Northern hemisphere, but poor in the
Southern one, and in both the Ethiopian and Australian regions it is
thought to be entirely wanting.
The species of the genus _Psithyrus_ (_Apathus_ of many authors) inhabit
the nests of _Bombus_; although less numerous than the species of the
latter genus, they also are widely distributed. They are so like _Bombus_
in appearance that they were not distinguished from them by the earlier
entomologists; and what is still more remarkable, each species of
_Psithyrus_ resembles the _Bombus_ with which it usually lives. There
appear, however, to be occasional exceptions to this rule, Smith having
seen one of the yellow-banded _Psithyrus_ in the nest of a red-tailed
_Bombus_. _Psithyrus_ is chiefly distinguished from _Bombus_ by the absence
of certain characters that fit the latter Insects for their industrial
life; the hind tibiae have no smooth space for the conveyance of pollen,
and, so far as is known, there are only two sexes, males and perfect
females.
{60}[Illustration: Fig. 23—_Psithyrus vestalis_, Britain. A, Female, x 3/2;
B, outer side of hind leg.]
The _Bombus_ and _Psithyrus_ live together on the best terms, and it
appears probable that the latter do the former no harm beyond appropriating
a portion of their food supplies. Schmiedeknecht says they are commensals,
not parasites; but it must be admitted that singularly few descriptions of
the habits and life-histories of these interesting Insects have been
recorded. Hoffer has, however, made a few direct observations which
confirm, and at the same time make more definite, the vague ideas that have
been generally prevalent among entomologists. He found and took home a nest
of _Bombus variabilis_, which contained also a female of _Psithyrus
campestris_, so that he was able to make observations on the two. The
_Psithyrus_ was much less industrious than the _Bombus_, and only left the
nest somewhat before noon, returning home again towards evening; after
about a month this specimen became still more inactive, and passed entire
days in the nest, occupying itself in consuming the stores of honey of its
hosts, of which very large quantities were absorbed, the _Psithyrus_ being
much larger than the host-bee. The cells in which the young of the
_Psithyrus_ are hatched are very much larger than those of the _Bombus_,
and, it may therefore be presumed, are formed by the _Psithyrus_ itself,
for it can scarcely be supposed that the _Bombus_ carries its complaisance
so far as to construct a cell specially adapted to the superior stature of
its uninvited boarder. When a _Psithyrus_ has been for some time a regular
inhabitant of a nest, the _Bombus_ take its return home from time to time
as a matter of course, displaying no emotion whatever at its entry.
Occasionally Hoffer tried the introduction of a _Psithyrus_ to a nest that
had not previously had one as an inmate. The new arrival caused a great
hubbub among the _Bombus_, which rushed to it as if to attack it, but did
not do so, and the alarm soon subsided, the _Psithyrus_ taking up the
position in the nest usually affected by the individuals of the species. On
{61}introducing a female _Psithyrus_ to a nest of _Bombus_ in which a
_Psithyrus_ was already present as an established guest, the latter
asserted its rights and drove away the new comer. Hoffer also tried the
experiment of placing a _Psithyrus campestris_ in the nest of _Bombus
lapidarius_—a species to which it was a stranger; notwithstanding its haste
to fly away, it was at once attacked by the _Bombus_, who pulled it about
but did not attempt to sting it.
When _Psithyrus_ is present in a nest of _Bombus_ it apparently affects the
inhabitants only by diminishing their stores of food to so great an extent
that the colony remains small instead of largely increasing in numbers.
Although _Bombus variabilis_, when left to itself, increases the number of
individuals in a colony to 200 or more, Hoffer found in a nest in which
_Psithyrus_ was present, that on the 1st of September the assemblage
consisted only of a queen _Bombus_ and fifteen workers, together with
eighteen specimens of the _Psithyrus_, eight of these being females.
The nests of _Bombus_ are destroyed by several animals, probably for the
sake of the honey contained in the pots; various kinds of small mammals,
such as mice, the weasel, and even the fox, are known to destroy them; and
quite a fauna of Insects may be found in them; the relations of these to
their hosts are very little known, but some undoubtedly destroy the bees'
larvae, as in the case of _Meloe_, _Mutilla_ and _Conops_. Birds do not as
a rule attack these bees, though the bee-eater, _Merops apiaster_, has been
known to feed on them very heavily.
The genera of social bees known as _Melipona_, _Trigona_ or _Tetragona_,
may, according to recent authorities, be all included in one genus,
_Melipona_. Some of these Insects are amongst the smallest of bees, so that
one, or more, species go by the name of "Mosquito-bees." The species appear
to be numerous, and occur in most of the tropical parts of the continents
of the world, but unfortunately very little is known as to their
life-histories or economics; they are said to form communities consisting
at times of a countless number of individuals; but it has not been
thoroughly ascertained whether these are the produce of a single queen, as
in the case of the hive-bee, or whether there may be more than one
egg-producer in each community. The late F. Smith thought the former of
these alternatives would prove to be correct. These mosquito-bees are
frequently spoken of as stingless bees, but this is not quite correct, for
although they do not sting, {62}von Ihering[34] says that all the essential
elements of the sting are present, the pointed or penetrating part of the
apparatus being stunted.
It would serve no useful purpose to attempt to construct the social history
of these stingless bees from the numerous brief scattered accounts in
entomological literature, for they refer to different species; it is,
however, positively stated by Smith on the authority of Peckolt[35] that
_Trigona mosquito_ sends off swarms after the manner of the hive-bee in
this country, and that after searching six hives only one royal female
could be found in each.
[Illustration: Fig. 24.—_Melipona_ sp. ♀. Amazons.]
The nests of many of these little bees are rich in honey, and they have a
host of enemies from man and monkeys downwards; and as they do not defend
themselves by stinging, it might be supposed they would have but a poor
time of it. From the accounts that have been published we may, however,
gather that they are rich in devices for the protection of their nests, and
for the exclusion of intruders. Bates has given some particulars as to
_Melipona interrupta_ (_fasciculata_); it is about one-third shorter than
the hive-bee, and its colonies are composed of an immense number of
individuals. The workers are usually occupied in gathering pollen; but they
also collect clay in a similar manner, and convey it to the nest, where it
is used for building a wall to complete the fortification of the nest,
which is placed either in a suitable bank, or in a trunk of a tree; in
either situation it is completely built in with clay. A nest which Bates
saw opened contained about two quarts of pleasantly-tasted liquid honey.
Forty-five species of these little bees were found in different parts of
the Amazons Valley, the largest kind being half an inch in length, the
smallest very minute, not more than one-twelfth of an inch. These little
creatures are thus masons as well as workers in wax and resin, and they are
also gatherers of nectar, pollen, and resin.
{63}According to Gosse, one of these bees is well known in Jamaica, where
they are called "Angelitos," in consequence of their not stinging people.
He observed a nest of this bee in a tree, and found it to be much infested
by black ants anxious to obtain entrance to it; three bees, however, stood
sentinel in the entrance, so as to completely block it and keep out
intruders, but the middle bee moved on one side out of the way directly one
of its fellows wished to come in or out of the nest. The honey accumulated
by this species is kept in clusters of cups about the size of a pigeon's
egg, at the bottom of the hive and away from the brood-cells. The queen or
mother-bee is lighter in colour than the others, and has the hind body
twice the length of theirs.
Hockings[36] has given us some details as to the natural history of two of
these bees that inhabit Australia, where they are called "Karbi" and
"Kootchar," the first being, it is supposed, _Trigona carbonaria_, Smith:
it is usually about three-sixteenths of an inch in length, the queen, when
fully developed, being nearly twice that length. The comb is built in a
most peculiar form, being, it is said, in the shape of a spiral staircase,
and tapering towards the ends: honey-pots and pollen are constructed for
the storage of food. The comb is encased in wax, and outside it a labyrinth
of waxen passages is formed. The entrance to the colony is guarded by a
line of bees who inspect every one that arrives, and it is surprising to
see how soon a stranger is discovered and pounced upon before it has time
even to alight; the intruder, when caught, is held by several bees, who put
it on the rack by holding and stretching out its limbs to their full
extent, retaining it in this position for as long as an hour, by which time
the unfortunate prisoner is usually dead. These bees, as well as many other
allied species, fight desperately with their mandibles, and are apparently
of a very fierce disposition. The other species, called "Kootchar," is said
to produce a very large number of drones, and the habits and dispositions
of the bees differ considerably from those of the "Karbi": the entrance to
their hive is guarded by a pipe of propolis (a sort of resinous wax) about
an inch in length, having an exceedingly sticky outer edge, and it is by
this pipe alone that access to the interior can be gained. At night the
entrance is closed by numerous minute globules of semi-fluid gum placed
against it, thus forming a thin wall full of air-holes. {64}The colonies of
"Kootchar" can be united by taking away a queen and then packing her
brood-nest, bees and all, against that of the colony it is to be joined to.
This cannot be done with the "Karbi." The account given by Mr. Hockings
contains a great many other interesting details, and there can be no doubt
that a full account of the natural history of these Insects would be very
instructive.
Fritz Müller has recorded a singular case bearing on the instinct of these
social Insects: he says that a nest of a small _Trigona_ was built in a
hollow tree, and that as a consequence of the irregularity of the hole the
bees were obliged to give a very irregular shape to their combs of honey.
These bees were captured and put in a spacious box (presumably together
with the irregular comb, but this he unfortunately does not mention): after
a year, "when perhaps not a single bee survived of those which had come
from the canella tree," they still continued to build irregular combs,
though quite regular combs were built by several other communities of the
same species that he had kept. These bees, he also tells us, do not use
pure wax for the construction of their combs, but mix it with resin or gum
that gives it a peculiar odour and appearance. He captured two communities
of a common _Melipona_, one of which had the combs made of dark reddish
brown, the other of pale yellowish brown, wax, and in captivity in a
distant locality each of the two communities continued to form its comb in
the same way, thus showing the continuity that prevails in these cases as
long as circumstances permit. Müller thinks this due to imitation, but it
seems at least as probable that it is due to perception of the properties
of the nest. The nest has a certain colour that the worker-bee matches.
Several species of the _Melipona_ and _Trigona_ were imported from Brazil
to France, and kept there for some time in captivity by M. Drory. Girard
has published[37] some details as to these colonies, and is of opinion that
some of them indicate an intelligence or instinct superior to that of the
honey-bee. The queen-bee of _M. scutellaris_ seems to display more
intelligence than the corresponding sex of _A. mellifica_. The mode of
feeding the larvae apparently differs from that of _A. mellifica_, a
provision of pollen being first placed in the cell, then some honey; when
{65}sufficient food for the whole consumption of a larva is accumulated the
queen deposits an egg in the cell, which is at once completely closed by
the worker. The interior of the abode of these bees is quite dark, only a
very small orifice being left, and in this a sentinel is constantly on the
alert. The same writer states that _Trigona crassipes_ has the very
peculiar habit of always locating its brood-comb in the nest of a species
of _Termes_.
The honey-bee, _Apis mellifica_ (Fig. 6), is considered the highest form
attained by the Anthophilous division of the Hymenoptera. The
differentiation of the three forms, male, female, and worker, is here
carried to a greater degree of perfection than in the other bees. The
drones are the males; the individuals we see gathering honey are always
workers, neither the male nor the female in this species taking any part in
procuring food for themselves or for the colony. In addition to this the
colonies formed may be described as permanent: they do not come to an end
at the close of one season, and provision is made for the formation of a
new colony while the old one still persists, by means of a peculiar process
called swarming. The life-history of _Apis mellifica_ and its anatomy and
physiology have been discussed in a whole library of works, and we need
only notice the chief features. When a swarm of bees leaves a hive it
consists of the queen-bee or female, and a number of workers, these latter
being, in fact, the surplus population that has been produced in the hive.
The swarm is not a nuptial flight, as is often supposed, but an act of
emigration. When this swarm has been housed, the bees commence operations
in their new quarters, by secreting wax; they are enabled to do this by
having consumed much saccharine food; the wax is produced by means of
glands in the hind-body over the inner faces of the ventral plates of the
abdominal rings, and it makes its appearance there, after passing from the
interior of the body through some peculiar membranes on the ventral
segments, in the form of thin projecting plates. These the bee takes off
with an apparatus on the hind pair of legs and applies, after working up
with the mandibles, to form the cells in which young ones are to be reared
and food stored. A large number of bees working in common thus produce the
regular and beautiful structure known as the comb; the queen afterwards
lays an egg in each cell, and as these soon hatch, great labour is thrown
on the workers, which have then to feed the young; this {66}they do by
eating honey and pollen, which, being formed into a sort of pap by a
portion of their digestive organs, is then regurgitated and given to the
young, a quantity of it being placed in the cell, so that the larva is
bathed by it, and possibly may absorb the food by the skin as well as the
mouth. When the colony is in good progress and young bees emerge, these act
as nurses, the older ones cease to prepare food and act as foragers,
bringing in honey and pollen which are each stored in separate cells. The
larva in the cell increases its size and sheds a very delicate skin several
times; when the larva has reached its full size no more food is supplied,
but the worker-bees seal up the cell by means of a cover formed of pollen
and wax, in such a manner as to be pervious to air: sealed up in the cell
the larva spins a cocoon for itself, remains therein for a little time as a
larva, then changes to a pupa, and thereafter bites its way out through the
cover of the cell, and appears for the first time as a new being in the
form of a worker-bee; the whole process of development from the egg-state
to the perfect condition of the worker-bee occupies about three weeks.
When the denizens of a hive are about to produce another queen, one or more
royal cells are formed; these are much larger than the ordinary
worker-cells, and of a quite different form. In this cell is placed an egg,
not differing in any respect from the egg that, if placed in an ordinary
cell, produces a worker; when the egg has produced a larva this is tended
with great care and fed throughout its life with royal jelly. This food
appears to be the same as that supplied to an ordinary worker-larva when it
is first hatched; but there is this difference, that whereas the
worker-larva is weaned, and supplied, after the first period of its
existence, with food consisting largely of honey, pollen and water, the
queen-larva is supplied with the pap or royal jelly until it is full grown.
Some difference of opinion exists as to this royal jelly, some thinking
that it is a different substance from what the workers are fed with; and it
is by no means improbable that there may be some difference in the
secretion of the glands that furnish a part of the material composing the
pap. The queen is produced more rapidly than workers are, about sixteen
days being occupied in the process of her development. Only one queen is
allowed in a hive at a time; so that when several queen-cells are formed,
and {67}queen-larvae nurtured in them, the first one that is developed into
a perfect queen goes round and stings the royal nymphs to death while they
are still in their cells. The production of drones is supposed to depend
chiefly on the nature of the egg laid by the queen; it being considered
that an unfertilised egg is deposited for this purpose. There is still some
doubt on this point, however. Though there is no doubt that drones are
produced in great numbers from unfertilised eggs, yet there is not evidence
that they cannot also be produced from fertilised eggs.[38] The drone-cells
are somewhat larger than the ordinary worker-cells, but this is probably
not of much import, and it is said that the larvae intended to produce
drones receive a greater proportion of pap than worker-larvae do: about
twenty-four days are required to produce a drone from the egg.
From this sketch it will be seen that the production of the worker (or
third sex, as it is improperly called, the workers being really females
atrophied in some points and specially developed in others) is dependent on
the social life, in so far at any rate as the special feeding is concerned.
There is good reason for supposing that _A. mellifica_ has been kept in a
state of domestication or captivity for an enormous period of time; and
this condition has probably led to an increase of its natural
peculiarities, or perhaps we should say to a change in them to suit a life
of confinement. This is certainly the case in regard to swarming, for this
process takes place with comparative irregularity in _Apis mellifica_ in a
wild condition. The killing of superfluous queens is also probably a
phenomenon of captivity, for it varies even now in accordance with the
numbers of the colony. It is interesting to notice that in confinement when
a swarm goes from the hive it is the old queen that accompanies it, and
this swarm as a rule settles down near the old hive, so that the queen-bee
being already fertilised, the new swarm and its subsequent increase are
nothing but a division of the old hive, the total products of the two
having but a single father and mother. When a second swarm goes off from a
hive it is accompanied by a young queen, who frequently, perhaps, in the
majority of cases, is unfertilised; this swarm is apt to fly for long
distances, so that the probability of cross-fertilisation is {68}greatly
increased, as the fertilisation of the young new queen is effected during a
solitary flight she makes after the colony has settled down. But in a state
of nature the colonies do not send off swarms every year or once a year,
but increase to an enormous extent, going for years without swarming, and
then when their home is really filled up send off, it may be presumed, a
number of swarms in one year. Thus the phenomena of bee-life in a wild
condition differ considerably from those we see in artificial confinement.
And this difference is probably greatly accentuated by the action of
parasites, the proportions of which to their guests are in a state of
nature liable to become very great; as we have seen to be the case in
_Bombus_.
Under these circumstances it is not a matter for surprise when we find that
the honey-bee has formed distinct races analogous to those that exist in
the case of the domesticated vertebrate animals. The knowledge of these
races is, however, at present very little advanced, and is complicated by
the fact that only imperfect information exists as to the true species of
the genus _Apis_. There is a bee very like our common honey-bee found in
southern Europe called _A. ligustica_; this is certainly a variety of _A.
mellifica_, and the same remark applies to a bee found in Egypt, and called
_A. fasciata_. This gives the honey-bee a very wide distribution, extending
possibly over the whole of the palaearctic region: besides this, the
species has been introduced into various other parts of the world.
According to Karsch the honey-bee shows in Germany several varieties, all
of which belong to the northern form, which may be spoken of as the _A.
domestica_ of Ray; the _A. ligustica_ and _A. fasciata_ form as we have
said distinct races, and it is a remarkable fact that these races remain
distinct even when imported into other climates; though for how long a
period of time this remains true there is very little evidence to show. The
northern form, _A. domestica_, is now found in very widely separated parts
of the world, in some of which it is wild; Smith mentions it as occurring
in the West India islands, throughout the North American continent as far
south as Mexico, even in Central and Southern Africa, and in Australia and
New Zealand. The var. _ligustica_ has been found also at the Cape of Good
Hope. The other species known of the genus _Apis_ all belong to the Old
World, so that there is very little doubt that _A. mellifica_ is also {69}a
true native of the eastern hemisphere, and its original home may possibly
have been not far from the shores of the eastern portion of the
Mediterranean sea. Seven or eight other species of _Apis_ are known, all
but one of which occur in Asia, extending as far as Timor and Celebes. The
exceptional one, _A. adansonii_, occurs in tropical Africa and in
Madagascar. Gerstaecker thought these species might be reduced to four, but
Smith's statement that the males and even the workers show good distinctive
characters seems to be correct. Very little is known as to the honey-bees
of China and Japan.
The queen-bee greatly resembles the worker, but has the hind body more
elongated; she can, however, always be distinguished from the worker by the
absence of the beautiful transverse, comb-like series of hairs on the inner
side of the first joint of the hind foot, the planta, as it is called by
the bee-keeper: she has also no wax plates and differs in important
anatomical peculiarities. The male bee or drone is very different, being of
much broader, more robust build, and with very large eyes that quite meet
in the middle of the upper part of the head: he also has the hind leg
differently shaped. The form of this limb enables the male of _A.
mellifica_ to be distinguished from the corresponding sex of allied species
of the genus.
[Illustration: Fig. 25.—Portions of hind-feet, 1, of male, 2, of worker, 3,
of queen, of the honey-bee; series on the left, outer faces; on the right,
inner faces. _a_, Tip of tibia: _b_, first joint; _c_, second joint of
tarsus.]
We are indebted to Horne for some particulars as to the habits of _A.
dorsata_, an allied East Indian species. He informs us that these bees
greatly disfigure buildings, such as the Taj Mahal at Agra, by attaching
their pendent combs to the marble arches, and are so pertinacious that it
is almost useless to destroy the nests. This bee is said to be so savage in
its disposition that it cannot be domesticated; it attacks the sparingly
clad Hindoos {70}with great ferocity when they disturb its nest.
Notwithstanding its inclination and power to defend its societies this
Insect appears to be destroyed wholesale. Colonel Ramsay failed to
establish hives of it, because the Insects were eaten up by lizards. The
crested honey-buzzard carries off large portions of the comb, and devours
it on a branch of some tree near by, quite regardless of the stings of the
bees; while the fondness of bears for the honey of the "Dingar," as this
species is called, is well known.
Note to P. 33: It has just been discovered that a most remarkable
symbiosis, with structural modification of the bee, exists between the
females of _Xylocopa_, of the Oriental sub-genus _Koptorthosoma_, and
certain Acarids. A special chamber, with a small orifice for entry,
exists in the abdomen of the bee, and in this the Acari are lodged.—See
Perkins, _Ent. Mag._ xxxv. 1899, p. 37.
Note to P. 80: referring to the habits of social wasps in warm countries.
The anticipation we ventured to indulge in is shown to be correct by the
recent observations of Von Ihering.[39] He states that social wasps in
Brazil may be divided into two great groups by their habits, viz. 1.
Summer communities, lasting for one year, and founded annually by
fertilised females that have hibernated—example, _Polistes_; 2. Perennial
communities, founded by swarms after the fashion of bee
colonies—examples, _Polybia_, _Chartergus_.
Note to Vol. V. Pp. 545, 546: The development of _Encyrtus fuscicollis_
has now been studied by Marchal, who has discovered the existence of
embryonic dissociation. The chain of embryos and the epithelial tube in
which they are placed, are formed as follows: the _Encyrtus_ deposits an
egg in the interior of the egg of the _Hyponomeuta_. This does not kill
the egg of the Lepidopteron, but becomes included in the resulting
caterpillar. The amnion of the Chalcid egg lengthens, and forms the
epithelial tube; while the cells within it become dissociated in such a
way as to give rise to a chain of embryos, instead of a single
embryo.—_C.R. Ac. Paris_, cxxvi. 1898, p. 662, and translation in _Ann.
Nat. Hist._ (7), ii. 1898, p. 28.
{71}CHAPTER II
HYMENOPTERA ACULEATA _CONTINUED_—DIVISION II. DIPLOPTERA OR WASPS—
EUMENIDAE, SOLITARY TRUE WASPS—VESPIDAE, SOCIAL WASPS—MASARIDAE
DIVISION II. DIPLOPTERA—WASPS.
_Anterior wings longitudinally plicate in repose; the pronotum extending
back, so as to form on each side an angle reposing on the tegula; the
basal segments of the hind body not bearing nodes or scales; the hind
tarsi formed for simple walking. The species either solitary or social in
their habits; some existing in three forms, males, females, and workers._
[Illustration: Fig. 26—Upper aspect of pronotum and mesonotum of a wasp,
_Eumenes coarctata_. _a_, Angle of pronotum; _b_, tegula; _c_, base of
wing; _d_, mesonotum.]
This division of Hymenoptera includes the true wasps, but not the fossorial
wasps. The name applied to it has been suggested by the fact that the front
wings become doubled in the long direction when at rest, so as to make them
appear narrower than in most other Aculeata (Fig. 27). This character is
unimportant in function so far as we know,[40] and it is not quite constant
in the division, since some of the Masaridae do not exhibit it. The
character reappears outside the Diploptera in the genus _Leucospis_—a
member of the Chalcididae in the parasitic series of Hymenoptera—the
species of which greatly resemble wasps in coloration. A better character
is that furnished by the well-marked angle, {72}formed by the pronotum on
the dorsal part (Fig. 26). By a glance at this part a Diplopterous Insect
can always be readily distinguished.
Three families are at present distinguished in the Diploptera, viz.
Eumenidae, Vespidae and Masaridae. We anticipate that Eumenidae and
Vespidae will ultimately be found to constitute but one family.
FAM. 1. EUMENIDAE—SOLITARY TRUE WASPS.
_Claws of the feet toothed or bifid; middle tibiae with only one spur at
tip. Social assemblages are not formed, and there is no worker-caste, the
duties of nest-construction, etc., being performed solely by the female._
The Eumenidae, or solitary wasps, are very little noticed by the ordinary
observer, but they are nevertheless more numerous than the social Vespidae,
about 800 species being known. In Britain we have sixteen species of the
solitary, as against seven of the social wasps. The Eumenidae exhibit a
considerable diversity in form and structure; some of them have the pedicel
at the base of the abdomen very elongate, while in others this is so short
as to be imperceptible in the ordinary position of the body. A repetition
of similar differences of form occurs in the social wasps, so that
notwithstanding the difference in habits there seems to be no satisfactory
way of distinguishing the members of the two families except by the
structure of the claws and tibial spurs.
[Illustration: Fig. 27.—_Eumenes flavopicta_ ♀. Burma. The wings on the
left in the position of repose, to show folding.]
Fabre has sketched the habits of a species of _Eumenes_, probably _E.
pomiformis_. This _Eumenes_ constructs with clay a small vase-like
earthenware vessel, in the walls of which small stones are embedded (like
Fig. 28, B). This it fills with food for the young. The food consists of
caterpillars to the number of fourteen or sixteen for each nest. These
caterpillars are believed to be stung by the parent-wasp (as is the case in
the {73}fossorial Hymenoptera), but complete evidence of this does not seem
to be extant, and if it be so, the stinging does not completely deprive the
caterpillars of the capacity of movement, for they possess the power of
using their mandibles and of making strokes, or kicking with the posterior
part of the body. It is clear that if the delicate egg of the _Eumenes_ or
the delicate larva that issues from it were placed in the midst of a mass
of this kind, it would probably suffer destruction; therefore, to prevent
this, the egg is not placed among the caterpillars, but is suspended from
the dome covering the nest by a delicate thread rivalling in fineness the
web of the spider, and being above the mass of food it is safe. When the
young larva leaves the egg it still makes use of the shell as its
habitation, and eats its first meals from the vantage-point of this
suspension; although the mass of the food grows less by consumption, the
little larva is still enabled to reach it by the fact that the egg-shell
splits up to a sort of ribbon, and thus adds to the length of the
suspensory thread, of which it is the terminal portion. Finally the heap of
caterpillars shrinks so much that it cannot be reached by the larva even
with the aid of the augmented length of the suspensory thread; by this
time, however, the little creature has so much increased in size and
strength that it is able to take its place amongst the food without danger
of being crushed by the mass, and it afterwards completes its metamorphosis
in the usual manner.
[Illustration: Fig. 28—Nidification of solitary wasps: section through
nest, A, of _Odynerus reniformis_; B, of _Eumenes arbustorum_. _a_, The
suspended egg of the wasp; _b_, the stored caterpillars. (After André.)]
It is known that other species of _Eumenes_ construct vase-like nests; _E.
unguiculata_, however, according to an imperfect account given by Perris,
makes with earth a closed nest of irregular shape, containing three cells
in one mass. The saliva of these builders has the power of acting as a
cement, and of forming with the clay a very impenetrable material. One
species, _E. coarctata_, L. of this genus occurs in Britain. The clay
{74}nests (Fig. 29) of this Insect are often attached to the twigs of
shrubs, while those of the two species previously mentioned are usually
placed on objects that offer a large surface for fixing the foundations to,
such as walls. According to Goureau the larva of this species forms in one
corner of its little abode, separated by a partition, a sort of dust-heap
in which it accumulates the various débris resulting from the consumption
of its stores.
_Eumenes conica_, according to Horne, constructs in Hindostan clay-nests
with very delicate walls. This species provisions its nest with ten or
twelve green caterpillars; on one occasion this observer took from one cell
eight green caterpillars and one black. It is much attacked by parasites
owing, it is thought, to the delicacy of the walls of the cells, which are
easily pierced; from one group of five cells two specimens only of the
_Eumenes_ were reared.
[Illustration: Fig. 29—Nest of _Eumenes coarctata_: A, the nest attached to
wood; B, detached, showing the larva. _a_, the larva; _b_, the partition of
the cell. (After André.)]
_Odynerus_, with numerous sub-genera, the names of which are often used as
those of distinct genera, includes the larger part of the solitary wasps;
it is very widely distributed over the earth, and is represented by many
peculiar species even in the isolated Archipelago of Hawaii; in Britain we
have about fifteen species of the genus. The _Odynerus_ are less
accomplished architects than the species of _Eumenes_, and usually play the
more humble parts of adapters and repairers; they live either in holes in
walls, or in posts or other woodwork, or in burrows in the earth, or in
stems of plants. Several species of the sub-genus _Hoplopus_ have the
remarkable habit of constructing burrows in sandy ground, and forming at
their entry a curvate, freely projecting tube placed at right angles to the
main burrow, and formed of the grains of sand brought out by the Insect
during excavation and cemented together. The habits of one such species
were described by Réaumur, of another by Dufour; and recently Fabre has
added to the accounts of these naturalists some important information drawn
from his own observations on _O. reniformis_.
{75}[Illustration: Fig. 30.—_Odynerus antilope_ ♀. Britain.]
This Insect provisions its cell with small caterpillars to the number of
twenty or upwards (Fig. 28, A.) The egg is deposited before the nest is
stocked with food; it is suspended in such a manner that the suspensory
thread allows the egg to reach well down towards the bottom of the cell.
The caterpillars placed as food in the nest are all curled up, each forming
a ring approximately adapted to the calibre of the cell. Fabre believes
these caterpillars to be partly stupefied by stinging, but the act has not
been observed either by himself, Réaumur, or Dufour. The first caterpillar
is eaten by the wasp-larva from its point of suspension; after this first
meal has been made the larva is supposed to undergo a change of skin; it
then abandons the assistance of the suspensory thread, taking up a position
in the vacant chamber at the end of the cell and drawing the caterpillars
to itself one by one. This arrangement permits the caterpillars to be
consumed in the order in which they were placed in the cell, so that the
one that is weakest on account of its longer period of starvation is first
devoured. Fabre thinks all the above points are essential to the successful
development of this wasp-larva, the suspension protecting the egg and the
young larva from destruction by pressure or movement of the caterpillars,
while the position of the larva when it leaves the thread and takes its
place on the floor of the cell ensures its consuming the food in the order
of introduction; besides this the caterpillars used are of a proper size
and of a species the {76}individuals of which have the habit of rolling
themselves up in a ring; while, as the calibre of the tube is but small,
they are unable to straighten themselves and move about, so that their
consumption in proper order is assured. Some interesting points in the
habits of an allied species, _O._ (_Pterocheilus_) _spinipes_ have been
observed by Verhoeff; the facts as regards the construction and
provisioning of the cell are almost the same as in _O. reniformis_. The
species of _Odynerus_ are very subject to the attacks of parasites, and
are, it is well known, destroyed to an enormous extent by Chrysididae.
Verhoeff says that the wasp in question supplied food much infested by
entoparasites; further, that a fly, _Argyromoeba sinuata_, takes advantage
of the habit of the _Odynerus_ of leaving its nest open during the process
of provisioning, and deposits also an egg in the nest; the _Odynerus_
seems, however, to have no power of discovering the fact, or more probably
has no knowledge of its meaning, and so concludes the work of closing the
cell in the usual way; the egg of the _Argyromoeba_ hatches, and the maggot
produced feeds on the caterpillars the wasp intended for its own offspring.
Verhoeff observed that the egg of the wasp-larva is destroyed, but he does
not know whether this was done by the mother _Argyromoeba_ or by the larva
hatched from her egg. Fabre's observations on allied species of Diptera
render it, however, highly probable that the destruction is effected by the
young fly-larva and not by the mother-fly.
Mr. R. C. L. Perkins once observed several individuals of our British _O.
callosus_ forming their nests in a clay bank, and provisioning them with
larvae, nearly all of which were parasitised, and that to such an extent as
to be evident both to the eye and the touch. In a few days after the wasps'
eggs were laid, swarms of the minute parasites emerged and left no food for
the _Odynerus_. Curiously, as it would seem, certain of the parasitised and
stored-up larvae attempted (as parasitised larvae not infrequently do), to
pupate. From which, as Mr. Perkins remarks, we may infer that (owing to
distortion) the act of paralysing by the wasp had been ineffectual. Mr.
Perkins has also observed that some of the numerous species of Hawaiian
_Odynerus_ make a single mud-cell, very like the pot of an _Eumenes_, but
cylindrical instead of spherical. This little vessel is often placed in a
leaf that a spider curls up; young molluscs of the genus _Achatinella_ also
{77}avail themselves of this shelter, so that a curious colony is formed,
consisting of the _Odynerus_ in its pot, of masses of the young spiders,
and of the little molluscs.
Horne has recorded that the East Indian _O. punctum_ is fond of availing
itself of holes in door-posts where large screws have been; after the hole
has been filled with provisions, the orifice is covered over level with the
surface of the wood so that it eludes human observation. It is nevertheless
discovered by an Ichneumon-fly which pierces the covering with its
ovipositor and deposits an egg within.
The genus _Abispa_ is peculiar to Australia and includes some very fine
solitary wasps, having somewhat the appearance of very large _Odynerus_:
these Insects construct a beautiful nest with a projecting funnel-shaped
entrance, and of so large a size that it might pass for the habitation of a
colony of social wasps; it appears, however, that this large nest is really
formed by a single female.
The species of the genus _Rhygchium_ are also of insecticide habits, and
appear to prefer the stems of pithy plants as the nidus for the development
of the generation that is to follow them. Lichtenstein says that a female
of the European _R. oculatum_ forms fifteen to twenty cells in such a
situation, and destroys 150 to 200 caterpillars, and he suggests that, as
it is easy to encourage these wasps to nest in a suitable spot, we should
utilise them to free our gardens from caterpillars, as we do cats to clear
the mice from our apartments.
The East Indian _R. carnaticum_ seems to have very similar habits to its
European congener, adapting for its use the hollow stems of bamboos. Horne
has recorded a case in which a female of this species took possession of a
stem in which a bee, _Megachile lanata_, had already constructed two cells;
it first formed a partition of mud over the spot occupied by the bee, this
partition being similar to that which it makes use of for separating the
spaces intended for its own young. This species stores caterpillars for the
benefit of its larvae, and this is also the case with another Eastern
species, _R. nitidulum_. This latter Insect, however, does not nidificate
in the stems of plants, but constructs clay cells similar to those of
_Eumenes_, and fixes them firmly to wood. _Rhygchium brunneum_ is said by
Sir Richard Owen to obliterate hieroglyphic inscriptions in Egypt by its
habit of building mud {78}nests amongst them. An individual of this wasp
was found by Dr. Birch when unrolling a mummy—"There being every reason to
believe that the Insect had remained in the position in which it was found
ever since the last rites were paid to the ancient Egyptian."
FAM. 2. VESPIDAE—SOCIAL WASPS.
_Claws of the feet simple, neither toothed nor bifid, middle tibiae with
two spurs at the tip. Insects living in societies, forming a common
dwelling of a papery or card-like material; each generation consists of
males and females and of workers—imperfect females—that assist the
reproductive female by carrying on the industrial occupations._
The anterior wing possesses four submarginal cells, as in the Eumenidae.
The attention of entomologists has been more directed to the habits and
architecture than to the taxonomy of these Insects, so that the external
structure of the Insects themselves has not been so minutely or extensively
scrutinised as is desirable; de Saussure, the most important authority,
bases his classification of the Insects themselves on the nature of the
nests they form. These habitations consist of an envelope, protecting cells
similar in form to the comb of the honey-bee, but there is this important
difference between the two, that while the bee forms its comb of wax that
it secretes, the wasps make use of paper or card that they form from
fragments of vegetable tissue,—more particularly woody fibre—amalgamated by
means of cement secreted by glands; the vegetable fragments are obtained by
means of the mandibles, the front legs playing a much less important part
in the economy of the Vespidæ than they do in that of the bees and
fossorial Hymenoptera.
In most of the nests of Vespidæ the comb is placed in stages or stories one
above the other, and separated by an intervening space, but in many cases
there is only one mass of comb. It is the rule that, when the cells of the
comb are only partially formed, eggs are deposited in them, and that the
larva resulting from the egg is fed and tended by the mother, or by her
assistants, the workers; as the larvae grow, the cells are increased in
correspondence with the size of the larva; the subsequent metamorphosis to
pupa and imago taking place in the cells after they have been entirely
{79}closed. The food supplied is of a varied nature according to the
species, being either animal or vegetable, or both.
[Illustration: Fig. 31—Section of the subterranean nest of the common wasp,
_Vespa germanica_, in position. (After Janet.) _a_, One of the chambers of
an ant's nest, _Lasius flavus_, placed above the wasps' nest; _b_, root to
which the first attachment of the nest was made; _c_, secondary
attachments; _d_, the first-made attachment; _e_, a flint within the
envelopes of the nest; _f_, the chief suspensory pillar of the second layer
of comb; _g_, lateral galleries; _h_, one of the secondary pillars of
suspension between two layers of comb; _i_, the layers of wasp-paper
forming the envelope of nest; _j_, vacant space round the nest; _k_, flints
that fell to the bottom during the work of excavation; _l_, numerous larvae
of a fly, _Pegomyia inanis_ (?) placed vertically in ground beneath the
nest; _m^1_ to _m^7_, the layers of comb, in _m^2_ the cells are indicated,
in _m^8_ (above the main figure) the arrangement of the three cells forming
the commencement of the new layer of comb, _m^7_, is shown; _n_, gallery of
access from surface; _o_, burrow of a mole; _p_, interval of 90 mm. between
top of nest and surface; _q_, height of the nest, 163 mm.]
Although the nests of the social wasps are very elaborate constructions,
yet they serve the purposes of the Insects for only a single season. This
is certainly the case in our own country. Here each nest is commenced by a
single female or queen; she at first performs unaided all the duties for
the inauguration of the colony; she lays the foundation of the cells,
deposits the eggs in them, feeds the young, and thus rears a brood of
workers that at once assist her, and for the future relieve her of a
considerable portion of her former occupations; the nest is by them added
to and increased, till the cold weather of the autumn is at hand; at this
time many males and females are produced; the cold weather either destroys
the inhabitants of the nest, or reduces their vitality so that it is
impossible for them to pursue successfully the avocations necessary for
their subsistence, and {80}they succumb to adversity. The young females,
however, hibernate, and each one that lives through the winter is the
potential founder of a new nest in the way we have already described. It
might be supposed that in tropical countries where no cold season occurs
the phenomena would be different, that the colonies would be permanent, and
that the nests would be inhabited until they were worn out. De Saussure,
however, informs us that this is not the case, but that in the tropics also
the colonies die off annually. "The nests are abandoned," he says, "without
it being possible to discover the reason, for apparently neither diminution
of temperature nor scarcity of food cause them (the Insects) to suffer. One
is tempted to suppose that the death of the Insects is the result of a
physiological necessity."
NESTS OF SOCIAL WASPS.—In Europe wasps' nests disappear very soon after
they are deserted. As it would appear from de Saussure's conclusions that
in the tropics as well as in the temperate regions the rule is that the
colonies endure only a portion of one year, and that a new nest is
commenced by a single founder once in twelve months, it is a somewhat
remarkable fact that some tropical wasp-nests are much more durable than
the lives of the inhabitants require, so that solidly constructed nests are
often found hanging to the trees long after they have been deserted, and
are sometimes overgrown with moss. Cuming has recorded the fact that he
found in South America an old wasp-nest that had been taken possession of
by swallows. We do not assign, however, much importance to the views of de
Saussure, because we may anticipate that enquiry will reveal much variety
in the habits of tropical and sub-tropical wasps. It is known that species
exist that store up honey, after the fashion of bees, and von Ihering has
recently shown[41] that in Brazil, species of several genera form new
colonies by swarming, after the manner of bees. So that it is possible that
certain colonies may remain for a long period in the same nest.
Much more variety exists in wasps' nests than would be supposed probable;
those formed by some of the tropical species of Vespidae are enveloped in
so solid and beautifully constructed an envelope of papier-maché, that they
resist with complete success the torrential rains of the tropics; while
some of those found in our own country are made of extremely soft and
delicate paper, {81}which is probably chiefly glandular products. Our
British Vespidae number only eight species, all belonging to the one genus
Vespa, and yet they exhibit three different modes of nidification. _Vespa
vulgaris_, _V. germanica_ and _V. rufa_ form subterranean nests, while _V.
arborea_, _V. sylvestris_ and _V. norvegica_ suspend their habitations from
the branches of trees, bushes, or strong annual plants. _Vespa crabro_, the
hornet, usually adopts an intermediate course, forming its nest above
ground, but in a spot where it is protected and concealed. The favourite
habitat of this formidable Insect is the interior of an old tree, but the
hornet will sometimes avail itself of the protection of a thatched roof.
Both it and other arboreal species are said, however, to occasionally make
subterranean nests. It is ascertained that _V. austriaca_, the eighth
species, is an inquiline.
[Illustration: Fig. 32—Nest of (?) _Polybia_ sp. The envelope partly cut
open; _o_, entrance. (After de Saussure.)]
De Saussure,[42] the monographer of the social wasps, classifies them
according to the architecture of their nests. He establishes three groups:
(1) Stelocyttares, in which the layers of comb are not connected with the
envelope, but are supported by pillars made by the wasps (Fig. 31); (2)
Poecilocyttares, an unsatisfactory group of which the chief characteristics
appear to be that the nest is always covered by an envelope, and the comb
is supported by an object such as the branch of a tree, round, or on, which
the envelope is placed (Fig. 32); (3) Phragmocyttares, in which the layers
of comb are supported, in part or entirely, by the envelope of the nest,
communication being effected by a hole in each layer of the comb (Fig. 33).
de Saussure's classification is far from satisfactory. There are many
social wasps that construct nests destitute of any proper envelope; as an
example of this, we may mention the species of {82}the abundant genus
_Polistes_; these Insects make hexagonal cells, of paper-like material,
forming an irregular comb, or mass, attached to bushes by a stalk near its
centre; these nests are placed so that the mouths of the open cells look
downwards. The species of _Ischnogaster_ (Fig. 34) make layers of comb,
connected by a pedicel, but without any envelope; these Insects form a
section of Stelocyttares called Gymnodomes.
Most of the nests of the Poecilocyttares have only a single layer of comb.
The wasps of the genera _Synoeca_ and _Polybia_ have the habit of spreading
a layer of cells on a leaf, or on the bark of a tree, and of covering this
with an envelope that is pierced by a single orifice only, but that does
not rest on the cells, and so allows circulation of the Insects between the
cells and the envelope. This appears to be the arrangement in a nest of
_Synoeca cyanea_ preserved in the British Museum; in this construction a
large layer of cells is moulded on the branch of a tree, whose contour, for
a length of two or three feet, it consequently follows; while outside the
mass there is placed a continuous envelope, leaving a considerable distance
between it and the cells.
It would be impossible in the space at our disposal to give a satisfactory
account of all the forms of wasp-nests, and we must therefore refer the
student to de Saussure's work, confining ourselves to a brief notice of
some specially interesting forms. The habitation of the Brazilian _Polybia_
(_Myrapetra_) _scutellaris_ is a very solid, closed structure, covered
externally with rough knobs or angular projections. Although of very large
size—it may be upwards of two feet in length—it is suspended from a branch,
and has but one orifice; the arrangement of the combs in the interior is
that of the Phragmocyttares, they being firmly attached to the outer
envelope, and so placed as to form a curved surface, the convexity of which
is downwards: the number of wasps in a well-developed nest of this kind
must be very great. This species is said to be a honey-gathering wasp.
One of the best known of the South American wasps' nests is the
construction (Fig. 33) of _Chartergus chartarius_; these nests are so
regularly shaped, and formed of papier-maché so compact and solid, as to
look like stone: this edifice is attached in a very firm manner to the
branch of a tree, and has a single portal of entry beneath; its interior
arrangement is much like that of _Myrapetra scutellaris_.
{83}A very remarkable wasp's nest is preserved in the British Museum of
Natural History; it is considered to be the work of _Montezumia dimidiata_
Sauss. an Eumenid wasp; it is a large mass of cells encircling the branch
of a tree, which therefore projects somewhat after the manner of an axle
through the middle: the cells are very numerous, and are quite as regular
as those of the most perfect of the combs of bees: the mass is covered with
a very thick layer of paper, the nest having somewhat the external
appearance of half a cocoa-nut of twice the usual size.
[Illustration: Fig. 33—Section of nest of _Chartergus chartarius_. South
America, _o_, Entrance. (After de Saussure.)]
_Apoica pallida_, a South American Insect, forms a nest in a somewhat
similar manner to _Polistes_, but it is covered on its outer aspect by a
beautiful paper skin, so that the nest looks somewhat like a toadstool of
large size attached to the branch of a tree.
The nests of the Insects of the genus _Polybia_—which we have already
mentioned as located by de Saussure in his unsatisfactory group
Poecilocyttares—usually have somewhat the form and size of pears or apples
suspended to twigs of trees or bushes; these little habitations consist of
masses of cells, wrapped in wasp-paper, in which there are one or more
orifices for ingress and egress. Smith says that the combs in the nest of
_P. pygmaea_ are of the most exquisite construction, and that it is by no
means an uncommon circumstance to find the outer envelope of the nest
ornamented with patches of delicate hexagonal tracery. This nest is about
the size of an orange.
We have already noticed the variety of nests formed by our British species
of the genus _Vespa_; in other parts of the world the edifices formed by
species of _Vespa_ attain a very large size. _V. crabroniformis_ in China,
and _V. velutina_ in India, make nests several feet or even yards in
length, inhabited by an enormous number of individuals; they are apparently
constructed of a material like brittle paper, and are arranged much like
the nests of our British hornet, _V. crabro_. _Vespa orientalis_ mixes a
considerable quantity of earth with the paper it uses for its
{84}constructive efforts. In the British Museum collection there is a nest
said to be that of the Japanese hornet, _V. japonica_. This is completely
covered by a paper envelope, and has apparently only a single small orifice
for ingress and egress. In the same collection there is a nest from Bahia
(believed to be that of a social wasp, though of what species is unknown),
the outer wall of which is apparently formed entirely of earth, and is a
quarter or half an inch thick: the comb inside appears also to be formed of
clay, the whole forming an elaborate construction in pottery. One is
tempted to believe it may prove to be the production of a social Eumenid.
HABITS OF SOCIAL WASPS.—We have already briefly noticed the way in which a
colony of wasps is founded, but some further particulars as to the mode in
which the society is increased and developed may be mentioned. The
queen-wasp makes at first only a very small group of three or four
incomplete cells; each cell is at first circular, or nearly so, and
moreover is of smaller diameter than it will afterwards be. In each of the
first three or four incomplete cells an egg is laid, and more cells are
commenced; but as the eggs soon hatch and produce larvae that grow rapidly,
the labours of the queen-wasp are chiefly directed to feeding the young. At
first she supplies them with saccharine matter, which she procures from
flowers or fruits, but soon gives them a stronger diet of insect meat. This
is procured by chasing living Insects of various kinds. Some species of
wasps prefer particular kinds of Insects, and the hornet is said to be very
fond of the honey-bee, but as a rule Diptera are the prey selected. When an
Insect has been secured, the hard and innutritious parts are bitten off,
and the succulent parts, more especially the thorax which contains chiefly
muscular tissue, are reduced to a pulp by means of the mandibles; this is
offered to the larvae, which are said to stretch out their heads to the
mother to receive the food, after the manner of nestling birds. When a
larva is full grown it spins a cocoon in the cell and changes to a pupa. It
is said by some entomologists that the queen-wasp closes the cell for the
purpose of the larval metamorphosis; but this is contradicted by others,
and is probably erroneous. In about a month, or a little less, from the
time of deposition of the egg, the perfect Insect is ready for issue, and
almost immediately after leaving its cell it assists in the work that is
going on for the development of the society. The {85}Insects produced at
this early period of the colony are exclusively workers, _i.e._ imperfect
females. They relieve the queen of the task of supplying the larvae with
food, and she henceforth remains within the nest, being, it is said,
herself fed by her workers; the society now rapidly increases in numbers,
and fresh combs are formed, the upper layer being always the oldest. About
the month of August, cells of larger size than those that have previously
been constructed are formed, and in these males and perfect females are
produced; in a few weeks after this the colony languishes and becomes
extinct. When it is no longer possible for the enfeebled wasps to carry out
their tasks of feeding the brood, they drag the larvae out of the cells and
destroy them. An uncertain number of queen-wasps seek protected nooks in
which to pass the winter, and each of these queens may be the founder of a
nest in the ensuing spring. It should be remarked that de Saussure states
that all the intermediate grades between perfect and imperfect females
exist, and Marchal's recent observations confirm this. There is in fact no
line of demarcation between worker and queen in the wasps as there is in
the honey-bee. Von Siebold long since drew attention to the existence of
parthenogenesis in certain species of wasps, and it appears probable that
it is of common occurrence.
Our knowledge of the social life of European wasps has recently been much
increased by the observations of two French naturalists, P. Marchal and C.
Janet. The latter has given an elaborate history of a nest of the hornet,
showing the rate and variations of increase in numbers. His observations on
this and other species indicate that warmth is of the utmost importance to
wasps; the Insects themselves create a considerable amount of heat, so that
the temperature of their abodes is much greater than that of the air. He
considers that in Europe an elevated temperature is essential for the
development of the individual,[43] and that the chief object of the various
wrappers of paper with which the Insects surround their nests is to keep up
this high temperature. These envelopes give a great deal of trouble to the
Insects, for they have to be repeatedly {86}destroyed and reformed, as the
combs they contain increase in size. Marchal's observations[44] relate
chiefly to the production of the sexes and worker-forms, in the
subterranean species, _Vespa germanica_ and _V. vulgaris_. The layers of
comb include cells of two sizes. The upper layers, which are the first
formed, consist of small cells only: the lower combs are constructed (at
Paris) early in August, and consist of larger cells from which males and
large females are reared. The males are, however, reared also in large
numbers in the small cells. If the queen be removed, the workers become
fertile, and produce parthenogenetically many eggs, but all of the male
sex. He entertains no doubt that even when the queen is in full vigour the
workers produce males if there is an abundant food supply.
The social wasps at present known number 500 or 600 species. _Polistes_ is
a very extensive genus, and it has also a very wide geographical
distribution; some of the species—and those found in widely-distant parts
of the world—are remarkable on account of their excessive variation in
colour, and it is worthy of note that the extreme forms have been more than
once taken from the same nest.
Next to _Polistes_, _Vespa_ is the most numerous in species, about 150
being known, and it is to this genus that all our British social wasps
belong. No Insects are better known in our islands than these wasps, owing
to the great numbers of individuals that occur in certain seasons, as well
as to their frequently entering our habitations and partaking of our food,
and to the terror that is occasioned by their supposed ferocity and desire
to sting. This last feature is a complete mistake; wasps never sting unless
they are roused to do so by attacks, or by considerable interference with
their work. The only real danger arises from the fact that a wasp may be
occasionally taken into the mouth with fruit, or may be handled unawares.
When they are flying about they are perfectly harmless unless attacked or
irritated, and even if they settle on the person no danger of their
stinging exists unless movement is made. Sichel correctly states that a
person may station himself close to a wasp's nest and remain there without
any risk at all, provided that he makes no movement; indeed, it is more
than probable that if no movement, or if only gentle {87}movement, be made,
the wasps are unaware of the presence of an intruder. It is, however, well
ascertained that if they are molested at their work, more especially when
they are actually engaged in the duties of the nest, they are then
extremely vindictive, and follow for a considerable distance those who have
irritated them. The East Indian _V. velutina_ is specially fierce when
aroused, and is said by Horne to have followed a party through dense jungle
for miles, and on some occasions to have stung animals, and even human
beings, to death.
[Illustration: Fig. 34—_Ischnogaster mellyi_. Java. A, Female imago (the
line at the side shows its length); B, nest, C, maxilla; D, labium; E,
mandible (tip downwards). The nest is probably upside down, although shown
here as by de Saussure.]
This vindictiveness is, however, only an exceptional mood due to some
interference with the colony. Even the hornet, notwithstanding its
threatening appearance, is harmless unless unduly provoked; its nests and
their inhabitants can be kept in domesticity, exhibited to strangers, even
moved from place to place, yet the hornets will not take offence if due
gentleness be observed. It is said that wasps will rear the progeny of a
neighbour in circumstances where this assistance is necessary. Hess has
related a case in which a queen-hornet had commenced a nest, and was killed
by an accident, leaving young brood in the comb {88}unprovided for: as a
result many of the helpless grubs died, and others were in a state of
starvation, when a strange queen-hornet appeared, associated itself with
the comb, and, adopting the orphan brood, nourished them and brought them
to their full size.
We have already alluded to the fact that, so far as external structure is
concerned, there is no great difference between the social and the solitary
wasps. Both, too, run through analogous series of forms and colours, and
the genus _Ischnogaster_ (Fig. 34) seems to connect the two groups by both
its structure and mode of life. The social habits are in many species only
inferred, and with greater knowledge will probably prove fallacious as a
guide to classification; indeed we have already said that in the genus
_Vespa_—perhaps the most perfectly social of all the wasps—there is one
species that has no worker, and that lives, it is supposed, as a parasite,
in the nests of its congeners. For this species, _V. austriaca_, it has
been proposed to create a separate genus, _Pseudovespa_, on account of this
peculiarity of habit, although no structural character has been detected
that could distinguish it. De Saussure has stated his conviction that
workers do not exist in some of the exotic genera, so that it appears
highly probable that with the progress of knowledge the present division
between social and solitary wasps will prove untenable.
Remains of Insects referred to the genera _Polistes_ and _Vespa_ have been
found in tertiary strata in various parts of Europe and in North America.
[Illustration: Fig. 35—_Masaris vespiformis_. A, male; B, female. Egypt.
(After Schaum.)]
FAM. 3. MASARIDAE.
_Anterior wing with two complete sub-marginal cells. Antennae usually
incrassate or clubbed at the extremity. Claws distinctly or obsoletely
dentate._
This is a group of fifty or sixty species with but few genera, {89}and most
of its components appear to be Insects of the greatest rarity. In their
appearance the Insects of this Family differ considerably from the other
Diploptera, and as the wings are only imperfectly, or not at all, plicate,
it must be admitted that the systematic affinities of the group require
reconsideration. The pronotal structure is, however, completely that of
Diploptera. The typical form of the Family, _Masaris vespiformis_, though
described a hundred years since, is a species of such extreme rarity, and
its sexes are so different, that entomologists have only recently been able
to agree about it. It has been found in Egypt and Algeria. The genera
_Ceramius_, _Jugurthia_, _Quartenia_ and _Coelonites_ are also members of
the Mediterranean fauna, while _Paragia_ is Australian, and _Trimeria_
South American. Several species of the genus _Masaris_ inhabit North
America, and Cresson has recently described another Masarid genus from the
same country, under the name of _Euparagia_.
The little that is known of their natural history is almost limited to an
account given by Giraud of the habits of _Ceramius lusitanicus_, of which
species he found a colony near Briançon. The Insect makes nests in the
earth; they are entered by means of a chimney-like passage analogous to
what is formed by certain _Odynerus_; the gallery when completed is about
six centimetres long, and at its extremity is an earthen cell in which the
larva lives; this is fed by the mother, who brings to it from time to time
a supply of a paste, described as being somewhat like dried honey. The
growth of the larva is believed to be rapid.
[Illustration: Fig. 36—Cells constructed by _Coelonites abbreviatus_.
(After André.)]
Some fragmentary observations made by Lichtenstein on _Coelonites
abbreviatus_ have also been recorded. This species, near Montpellier,
constructs earthen cells; they are not, however, subterranean, but are
placed side by side on the dry stems of plants (Fig. 36); these cells are
stored with a material similar to that supplied by _Ceramius lusitanicus_
to its young.
{90}CHAPTER III
HYMENOPTERA ACULEATA _CONTINUED_—DIVISION III. FOSSORES OR FOSSORIAL
SOLITARY WASPS—FAMILY SCOLIIDAE OR SUBTERRANEAN FOSSORS—FAMILY POMPILIDAE
OR RUNNERS—FAMILY SPHEGIDAE OR PERFECT-STINGERS
DIVISION III. FOSSORES.
_Aculeate Hymenoptera, in which the abdomen, though very diverse in form,
does not bear prominences on the upper aspect of the basal segments;
front wing without longitudinal fold along the middle; hairs of body not
plumose. Only two forms (male and female) of each species._
Fossorial Hymenoptera are distinguished from other Aculeates at present
only by negative characters, _i.e._ they are Aculeates, but are not ants,
bees or wasps. According to their habits they fall into four, by no means
sharply distinguished, groups—(1) those that form no special receptacles
for their young, but are either of parasitic or sub-parasitic habits, or
take advantage of the abodes of other Insects, holes, etc.; (2)
constructors of cells of clay formed into pottery by the saliva of the
Insect, and by drying; (3) excavators of burrows in the ground; (4) makers
of tunnels in wood or stems of plants. Several species make use of both of
the last two methods. The habits are carnivorous; the structures formed are
not for the benefit of the makers, but are constructed and stored with food
for the next generation. Their remarkable habits attracted some attention
even 2000 years or more ago, and were to some extent observed by Aristotle.
The great variety in the habits of the species, the extreme industry,
skill, and self-denial they display in carrying out their voluntary
labours, render them one of the most instructive groups of the animal
kingdom. There are no social or gregarious {91}forms, they are true
individualists, and their lives and instincts offer many subjects for
reflection. Unlike the social Insects they can learn nothing whatever from
either example or precept. The skill of each individual is prompted by no
imitation. The life is short, the later stages of the individual life are
totally different from the earlier: the individuals of one generation only
in rare cases see even the commencement of the life of the next; the
progeny, for the benefit of which they labour with unsurpassable skill and
industry, being unknown to them. Were such a solicitude displayed by
ourselves we should connect it with a high sense of duty, and poets and
moralists would vie in its laudation. But having dubbed ourselves the
higher animals, we ascribe the eagerness of the solitary wasp to impulse or
instinct, and we exterminate their numerous species from the face of the
earth for ever, without even seeking to make a prior acquaintance with
them. Meanwhile our economists and moralists devote their volumes to
admiration of the progress of the civilisation that effects this
destruction and tolerates this negligence.
[Illustration: Fig. 37.—_Sceliphron nigripes_ ♀ (Sub-Fam. Sphegides).
Amazons. × 3/2.]
{92}It should be noted that in the solitary as in the social Insects the
males take no part whatever in these industrial occupations, and apparently
are even unaware of them. It is remarkable that, notwithstanding this, the
sexual differences are in the majority less than is usual in Insects. It is
true that the various forms of Scoliidae exhibit sexual distinctions which,
in the case of Thynnides and Mutillides are carried to an extreme degree,
but these are precisely the forms in which skill and ingenuity are
comparatively absent, the habits being rather of the parasitic than of the
industrial kind, while the structure is what is usually called degraded
(_i.e._ wingless). The great difference between the habits of the sexes,
coupled with the fact that there is little or no difference in their
appearance, has given rise to a curious Chinese tradition with regard to
these Insects, dating back to Confucius at least.[45] The habit of stinging
and storing caterpillars in a cell, from which a fly similar to itself
afterwards proceeds having been noticed, it was supposed to be the male
that performed these operations; and that when burying the caterpillars he
addressed to them a spell, the burden of which is "mimic me." In obedience
the caterpillars produce the wasp, which is called to this day "Jiga," that
is in English "mimic me." The idea was probably to the effect that the
male, not being able to produce eggs, used charmed caterpillars to continue
the species.
SUMMARY OF THE PREY OF FOSSORES.
Group of Fossores. Food or Occurrence.
Fam. Scoliidae.
Sub-Fam. Mutillides As parasites on Hymenoptera Aculeata.
" Thynnides (?) Parasites on Lepidopterous pupae.
" Scoliides Larvae of Coleoptera [(?) spiders in the
case of _Elis 4-notata_].
" Rhopalosomides Unknown.
" Sapygides The provisions stored by bees. Caterpillars
(teste Smith).
Fam. Pompilidae Spiders. Rarely Orthoptera (Gryllidae and
Blattidae, teste Bingham) or Coleoptera.
Fam. Sphegidae.
Sub-Fam. Sphegides Orthoptera (especially Locustidae), larvae
of Lepidoptera, Spiders [(?) same species
(_Sceliphron madraspatanum_ and _Sphex
coeruleus_), both spiders and
caterpillars].
" Ampulicides Orthoptera (Blattidae only). {93}
" Larrides Orthoptera of various divisions. Aculeate
Hymenoptera, in the case of _Palarus_.
[Spiders stolen from nests of _Pelopaeus_
by _Larrada_.]
" Trypoxylonides Spiders, caterpillars, Aphidae.
" Astatides _Astata boops_ uses Pentatomid bugs,
cockroaches, and even Aculeate Hymenoptera
(_Oxybelus_, teste Smith).
" Bembecides Diptera and _Cicada_.
" Nyssonides Diptera, Homoptera (_Gorytes mystaceus_
takes _Aphrophora_ out of its "cuckoo-
spit").
" Philanthides Aculeate Hymenoptera (_Philanthus_). Hard
beetles, viz. Curculionidae, Buprestidae,
Chrysomelidae (_Cerceris_).
" Mimesides Small Homoptera, even Aphidae. Diptera
(Tipulidae) in Hawaii.
" Crabronides Diptera, Aphidae [? the same species of
wasps both of these]. Other small
Homoptera. Ants (in the case of
_Fertonius_). Parasitic Hymenoptera (in
the case of _Lindenius_).
Great diversity of opinion exists as to the classification of the Fossores.
This arises chiefly from the incomplete state of the collections studied,
and from the fact that the larger part of the works published are limited
to local faunae. Opinions as to the families vary; some admitting only
three or four, others upwards of twenty. After consideration of the various
views, the writer thinks it best to admit at present only three families,
which speaking broadly, correspond with habits, viz. (1) Scoliidae,
subterranean stingers; (2) Pompilidae, runners; (3) Sphegidae, stingers
above ground.
1. Scoliidae. Pronotum and tegulae in contact. Abdomen with the plane of
the ventral surface interrupted by a chink between the first and second
segments. Numerous wingless forms.
2. Pompilidae. Pronotum and tegulae in contact. Abdomen with the plane of
the ventral surface not interrupted by a chink. Legs very long. No
wingless forms.
3. Sphegidae. Pronotum and tegulae not in contact. No wingless forms.
We shall treat as sub-families those divisions of Scoliidae and Sphegidae
considered by many as families.
{94}FAM. 1. SCOLIIDAE.
The members of this family, so far as is known, display less perfect
instincts than the Sphegidae and Pompilidae, and do not construct cells or
form burrows. Information as to the habits is almost confined to European
forms. We adopt five sub-families.
SUB-FAM. 1. MUTILLIDES.—_The sides of the pronotum reach the tegulae: the
female is destitute of wings and ocelli, frequently having the parts of
the thorax so closely soldered that the divisions between them are
obliterated: the males are winged, furnished with ocelli, and having the
thoracic divisions distinct; intermediate tibiae with two apical spurs.
Front wing with two or three sub-marginal cells. The larvae live
parasitically at the expense of other Hymenoptera Aculeata._
The Mutillides have some resemblance to ants, though, as they are usually
covered with hair, and there is never any node at the base of the abdomen,
they are readily distinguished from the Formicidae. The great difference
between the sexes is their most striking character. Their system of
coloration is often very remarkable, the velvet-like pubescence clothing
their bodies being variegated with patches of sharply contrasted vivid
colour; in other cases the contrast of colour is due to bare, ivory-like
spaces. They have the faculty of stridulating, the position and nature of
the organ for the purpose being the same as in ants.
Very little exact information exists as to the habits and life-histories of
the species. Christ and Drewsen, forty or fifty years ago, recorded that
_M. europaea_ lives in the nests of bees of the genus _Bombus_, and Hoffer
has since made some observations on the natural history of the same species
in South East Europe, where this _Mutilla_ is found in the nests of ten or
eleven species of _Bombus_, being most abundant in those of _B. agrorum_
and _B. variabilis_; occasionally more individuals of _Mutilla_ than of
bees may be found in a nest. He supposes that the egg of the _Mutilla_ is
placed in the young larva of the _Bombus_, and hatches in about three days;
the larva feeds inside the bee-larva, and when growth is completed a cocoon
is spun in the interior of the pupa-case of the bee. When the perfect
Insects emerge, the males leave the nest very speedily, but the females
remain for some time feeding on the bees' honey. Females are usually
produced in greater numbers than males. This account leaves {95}much to be
desired. From the observations of Radoszkowsky it is clear that other
species of Mutillides are by no means confined to the nests of _Bombus_ but
live at the expense of Aculeate Hymenoptera of various groups. This
naturalist asserts that the basal abdominal segment of the parasite
resembles in form that of the species on which it preys.
The apterous condition of the females of Mutillides and Thynnides is very
anomalous in the Fossors; this sex being in the other families
distinguished for activity and intelligence. The difference between the
sexes is also highly remarkable. The males differ from the females by the
possession of wings and by the structural characters we have mentioned, and
also in a most striking manner in both colour and form; Burmeister, indeed,
says that in South America—the metropolis of Mutillides—there is not a
single species in which the males and females are alike in appearance; this
difference becomes in some cases so extreme that the two sexes of one
species have been described as Insects of different families.
[Illustration: Fig. 38—_Mutilla stridula._ Europe. A, Male; B, female.]
Upwards of one thousand species are assigned to the genus _Mutilla_, which
is distributed over the larger part of the world; there is so much
difference in these species as to the nervuration of the wings in the
males, that several genera would be formed for them were it not that no
corresponding distinctions can be detected in the females. Three or four
species of _Mutilla_ are described as being apterous in the male as well as
in the female sex; they are very rare, and little is known about them. Only
three species of Mutillides occur in Britain, and they are but rarely seen,
except by those who are acquainted with their {96}habits. The African and
East Indian genus, _Apterogyna_, includes some extremely peculiar
Hymenoptera; the males have the wing nervuration very much reduced, and the
females are very ant-like owing to the deep constriction behind the first
abdominal ring.
SUB-FAM. 2. THYNNIDES.—_Males and females very different in form; the
male winged, the front wing with three, or only two, sub-marginal cells;
the female wingless and with the thorax divided into three sub-equal
parts._
[Illustration: Fig. 39—_Methoca ichneumonides._ A, Male; B, female.
Britain.]
The Thynnides are by some entomologists not separated from the Mutillides;
but the distinction in the structure of the thorax of the females is very
striking. In the Thynnides the nervuration of the wing appears always to
extend to the outer margin, and in the Mutillides not to do so. This family
is represented in Britain by a single very rare Insect, _Methoca
ichneumonides_: to the unskilled observer the female would appear to be
without doubt an ant. This Insect is by some considered as the type of a
family distinct from the Thynnides proper. Thynnides are numerous in
Australia. Very little is really known as to their habits, though it has
been stated that they are parasitic on Lepidoptera, Bakewell having
obtained specimens from subterranean cocoons of that Order. Those who are
interested in differences between the sexes of one species should examine
the extraordinary examples of that phenomenon presented by the Thynnides;
the dissimilarity throughout the group—which is now of considerable
extent—being so extreme that no entomologist would from simple inspection
believe the two sexes to have any connection; but the fact that they are so
connected has been demonstrated beyond doubt. In very few {97}cases,
however, have the sexes been matched, so that at present males are no doubt
standing in the lists of Hymenoptera as one species and their females as
other species.
SUB-FAM. 3. SCOLIIDES.—_Pronotum reaching back to the tegulae; legs
stout; intermediate tibiae with one apical spur; both sexes winged; the
nervures not extending to the posterior_ (i.e. _distal_) _margin_.
This group includes some of the largest and most powerful of the Aculeate
Hymenoptera. Its members are usually hairy Insects with thick legs, the
colour being black, more or less variegated with bands or spots of red or
yellow; the hind body is elongate, has only a very short pedicel, and in
the male is usually terminated by three projecting spines. The pronotum is
of variable dimensions, but its front angles are always co-adapted with the
points of insertion of the front wings. The nervuration of the front wings
is confined to the basal part, the extensive apical or outer area
possessing no nervures. There is frequently a great difference in the size
of the two sexes of the same species, the female being very much larger
than the other sex. The larvae, so far as is known, devour those of
Lamellicorn Coleoptera.
[Illustration: Fig. 40.—_Scolia haemorrhoidalis_ ♀. Europe.]
Fabre has investigated the habits of some of the species of Scoliides found
in France, and has informed us that their means of subsistence consists of
larvae of the larger Lamellicorn beetles, _Cetonia_, _Oryctes_, _Anoxia_,
and _Euchlora_; these beetles belong to very different divisions of the
Lamellicornia, but they have in common the fact that their larvae are of
subterranean habits, living in the earth or in accumulations of débris in
which there is a large proportion of vegetable matter or roots. The female
_Scolia_ penetrates into the ground in order to find the Lamellicorn larvae
necessary as food for its progeny. _Scolia bifasciata_ {98}attacks the
larvae of several species of _Cetonia_, and _S._ (_Colpa_) _interrupta_
chooses the larvae of the chafers _Anoxia villosa_ and _A. matutinalis_.
The mother _Scolia_ enters the ground in August or September, and having
found a suitable larva stings it and deposits an egg on the ventral surface
of the prey; the paralysed larva is left where it was found, no attempt
being made to place it in a special receptacle. The egg is placed on the
ventral surface, well behind the feet, under a mass of matter in the
alimentary canal. Shortly after being hatched the young destroyer
penetrates with its head the skin of the victim, and in this position
commences to feed; it is necessary that it should obtain its food without
killing the _Cetonia_ larva, for it cannot prosper on decaying food, so
that if the _Cetonia_ larva die the _Scolia_ larva likewise perishes; the
latter, accordingly, does not withdraw its head from the interior of the
victim, but remains always in the same position, as it grows larger
extending its head forwards into the front part of the interior of its
victim; the internal organs of the latter are consumed in a systematic
order so as to delay bringing about its death till the last moment, and
thus all the interior of the _Cetonia_ larva is appropriated till nothing
remains but an empty skin. By a series of experiments, Fabre showed how
essential it is that this apparently revolting operation should be carried
on with all details strictly _en règle_. If the head of the _Scolia_ larva
be taken out from the victim and applied to another part of the body of the
_Cetonia_, the result is that it cannot eat; even if it be replaced in the
original situation, after being taken away, it frequently happens that the
_Cetonia_ larva dies, its death involving also that of the destroyer. It is
necessary, too, that the victim should be paralysed, for if an intact
_Cetonia_ larva be taken and bound down in such a position that it cannot
move, and if a small orifice in its skin be made in the proper spot and a
young _Scolia_ larva be placed on it, the little parasite will avail itself
of the opportunity and commence to feed on the larva provided for it, but
the latter will speedily die, and the _Scolia_ necessarily perishes with
it. Thus both the paralysis of the victim and the special mode of eating
are essential to the life of the _Scolia_. The operation of stinging the
larva so as to produce the necessary paralysis, or rather insensibility, is
a difficult one, and requires great skill and patience. The _Cetonia_ larva
is of large size, and must be pierced in one particular spot; {99}in order
to reach this the _Scolia_ mounts on its victim, and is frequently
dislodged by its struggles; sooner or later, however, the proper position
is obtained by the wasp, and the larva is then stung in the exact spot
necessary to allow the sting (and the poison introduced by it) to reach the
most important of the nervous ganglia that control the movements of the
body, this spot being, in the case of the _Cetonia_, the line of
demarcation between the pro- and meso-thorax, on the middle line of the
ventral surface of the body. The _Scolia_ gives but one sting to the
victim, and this it will not administer until it can do so exactly in the
proper place. This practice of devouring the victim slowly, without killing
it till all is eaten, is very widely spread in the Hymenoptera, and it is
satisfactory to find that we may infer from Fabre's observations that it is
not so horrible as it would at first appear; for it is probable that the
stinging prevents decomposition of the victim, not by reason, as some have
supposed, of the poison injected by the wasp having an antiseptic effect,
but rather by means of destroying sensibility, so that the creature does
not die from the pain, as it is believed it did in certain cases where
Fabre induced the young _Scolia_ larva to feed on a victim that had not
been stung. We may here remark that very little exact information exists as
to the operation of stinging. Fabre attaches great importance to the sting
being inflicted on a nerve-ganglion. Whether a sting that did not reach
this part might not have a sufficient effect appears, however,
doubtful.[46]
A remarkable form of Scoliides, with wings of smaller size than usual and
deeply divided, has been described by Saunders under the name _Pseudomeria
graeca_. Still more remarkable is _Komarovia victoriosa_ found in Central
Asia; in this Insect the male retains the appearance of a slender, pallid
_Scolia_, but the female differs totally in form, and has the peculiar
wings so reduced in size as to be useless for flight.
SUB-FAM. 4. SAPYGIDES.—_Closely allied to the Scoliides, but possessing
slender legs and antennae; also the first abdominal segment is less
disconnected from the second, so that the outline {100}is less
interrupted; the eyes are deeply emarginate; the hind body is not spinose
at the apex._
[Illustration: Fig. 41.—_Sapyga 5-punctata_ ♀, Britain.]
The economy of _Sapyga_, the only genus, has been the subject of difference
of opinion. The views of Latreille and others that these species are
parasitic upon bees is confirmed by the observations of Fabre, from which
it appears that _S. 5-punctata_ lives in the burrows of species of the
bee-genus _Osmia_, consuming the store of provisions, consisting of
honey-paste, that the bee has laid up for its young. According to the same
distinguished observer, the _Sapyga_ larva exhibits hypermetamorphosis
(_i.e._ two consecutive forms), and in its young state destroys the egg of
the bee; but his observations on this point are incomplete and need
repetition. We have two species of _Sapyga_ in Britain; they differ in
colour, and the sexes of _S. 5-punctata_ also differ in this respect; the
abdomen, spotted with white in both sexes is in the female variegate with
red. Smith found our British _Sapyga 5-punctata_ carrying caterpillars.
SUB-FAM. 5. RHOPALOSOMIDES.—_Antennae elongate, spinigerous; ocelli very
prominent; tarsi of peculiar structure, their claws bifid._
[Illustration: Fig. 42—_Rhopalosoma poeyi._ A, female imago; B, front of
head. Cuba. (After Westwood.)]
This sub-family has recently been proposed by Ashmead[47] for {101}an
extremely rare American Insect that had previously been placed by Cresson
among parasitic Hymenoptera. Westwood classed _Rhopalosoma_ among
Diploptera, saying of it "animal quoad affinitates excrucians." We
reproduce Westwood's figure, but not being acquainted with the Insect we
can express no opinion as to whether it is allied to the Scoliidae or to
the Sphegidae. The habits are, we believe, quite unknown.
FAM. 2. POMPILIDAE.
_Pronotum at the sides reaching the tegulae; hind body never definitely
pedicellate, though the first segment is sometimes elongate and conical;
hind legs long; eyes elliptic in form, not emarginate._
The Pompilidae are perhaps the most extensive and important of the groups
of Fossores, and are distributed over all the lands of the globe, with the
exception of some islands and of the inclement arctic regions. The sting of
the Pompilidae, unlike that of most of the Fossores, inflicts a burning and
painful wound; the creatures sometimes attain a length of two or three
inches, and a sting from one of these giants may have serious results.
Although there is considerable variety in the external form of the members
of the group, the characters given above will enable a Pompilid to be
recognised with approximate certainty. The elongation of the hind legs
includes all the parts, so that while the femur extends nearly as far back
as the extremity of the body—in dried examples at any rate—the tibiae and
the long tarsi extend far beyond it; thus these Insects have great powers
of running; they are indeed remarkable for extreme activity and vivacity.
They may frequently be seen running rapidly on the surface of the ground,
with quivering wings and vibrating antennae, and are probably then employed
in the search for prey, or some other of the operations connected with
providing a store of food for their young. Spiders appear to be their
special, if not their only, prey. Several authors have recorded details as
to the various ways in which the prey is attacked. Fabre has observed the
habits of several species, and we select his account of the _modus
operandi_ of species of the genera _Pompilus_ and _Calicurgus_, in their
attacks on poisonous spiders that inhabit holes in the ground or in walls.
The wasp goes to the mouth of the spider's burrow, and the latter then
dashes to the entry, apparently enraged at the audacity of its persecutor.
{102}[Illustration: Fig. 43.—_Calicurgus hyalinatus_ ♀. Britain.]
The _Calicurgus_ will not actually enter a burrow when there is a spider in
it, because if it did so the spider would speedily dispose of the aggressor
by the aid of its poisonous fangs. The _Calicurgus_, therefore, has
recourse to strategy with the object of getting the spider out of its nest;
the wasp seizes its redoubtable foe by one foot and pulls; probably it
fails to extract the spider, and in that case rapidly passes to another
burrow to repeat its tactics; sooner or later a spider is in some moment of
inattention or incapacity dragged from its stronghold, and, being then
comparatively helpless, feels itself at a disadvantage and offers but a
feeble resistance to the wasp, which now pounces on its body and
immediately inflicts a sting between the fangs of the foe, and thus at once
paralyses these dangerous weapons; thereafter it stings the body of the
spider near to the junction of the abdomen and cephalothorax, and so
produces complete inactivity. Having secured its prey, the wasp then seeks
a suitable hole in which to deposit it; probably an empty burrow of a
spider is selected for the purpose, and it may be at a height of several
feet in a wall; the Hymenopteron, walking backwards, drags its heavy prey
up the wall to bring it to the den. When this is accomplished an egg is
deposited on the spider, and the wasp goes in search of a fragment or two
of mortar, with which the mouth of the burrow is finally blocked. Fabre's
accounts refer to the habits of several species, and give a good insight
into some points of the instincts of both the spider and the wasp. It seems
that a sense of superiority is produced in one or other of the foes,
according as it feels itself in suitable conditions; so that though a
spider out of its burrow and on the ground is speedily vanquished by the
Pompilid, yet if the two be confined together in a vase, both are {103}shy
and inclined to adopt defensive or even evasive tactics, the result
probably being that the wasp will be killed by the spider during the night,
that being the period in which the attacking powers of the spider are more
usually brought into play.
It seems to be the habit of some _Pompilus_ to procure a victim before they
have secured a place for its reception; and Fabre took advantage of this
fact, and made very interesting observations on some points of the instinct
of these wasps. Having found a _Pompilus_ that, after having caught a
spider and paralysed it, was engaged in making a retreat for its reception,
he abstracted the booty, which was deposited at the top of a small tuft of
vegetation near to where the _Pompilus_ was at work. In this case the
burrow in course of preparation was subterranean, and was formed by the
_Pompilus_ itself, which therefore could not, while it was engaged
underground, see what took place near it. It is the habit of the wasp to
leave its work of excavation from time to time, and to visit the prey as if
to assure itself of the safety of this object, and to enjoy the
satisfaction of touching it with the mouth and palping it. Desirous of
testing the wasp's memory of locality, Fabre took the opportunity, while
the Insect was working at the formation of its burrow, of removing, as we
have said, the booty from the place where it had been deposited, and
putting it in another spot some half-yard off. In a short time the
_Pompilus_ suspended work and went straight to the spot where it had
deposited its property, and finding this absent, entered on a series of
marches, counter-marches, and circles round the spot where it had left the
prey, as if quite sure that this was really the place where the desired
object ought to be. At last convinced that the paralysed prey was no longer
where it had been placed, the _Pompilus_ made investigations at a greater
distance and soon discovered the spider. Fabre recounts that its movements
then appeared to indicate astonishment at the change of position that it
thus ascertained to have occurred. The wasp, however, soon satisfied itself
that this was really the very object it was seeking, and seizing the spider
by the leg slightly altered its position by placing it on the summit of a
small tuft of vegetation; this latter proceeding being apparently always
carried out by this species of _Pompilus_. Then it returned to its
excavation, and Fabre again removed the spider to a third spot; the wasp
when it next rested from its work made its way {104}immediately to the
second spot, where it had last left the spider, thus showing that it
possessed an accurate memory for locality; the wasp was very much surprised
at the absence of the valued prize and persisted in seeking it in the
immediate vicinity without once returning to the place where it had been
first located. Fabre repeated this manoeuvre five times, and the _Pompilus_
invariably returned at once to the spot where it had last left its prey.
The acute memory for localities displayed by this Insect seems to be more
or less general throughout the Aculeate Hymenoptera, and is of very great
importance to them. The power of finding the object appears to depend on
sight, for when Fabre, after removing the spider to a fresh spot, made a
slight depression in the ground, placed the spider in it and covered it
over with a leaf, the wasp did not find it. At the same time, the Insect's
sight must be a very different sense from our own, for the wasp, when
seeking its lost booty, frequently passed within a couple of inches of it
without perceiving it, though it was not concealed.
Belt gives an example of the habits of the Mexican _Pompilus polistoides_.
He noticed it, when hunting for spiders, make a dart at a web in the centre
of which a spider was stationed; by this movement the creature was
frightened and fell to the ground, where it was seized by the wasp and
stung. The _Pompilus_ then dragged its prisoner up a tree and afterwards
flew off with it, the burden being probably too heavy for conveyance to the
nest without the vantage of an elevation to start from.
Several modifications adopted by Pompilidae in their mode of stinging their
spider-victims have been recorded by Ferton; these we cannot allude to in
detail, but will nevertheless mention that one species stings the body of
its spider-prey at random, and that in other cases it would appear that the
paralysis of the spider is evanescent. In short, there are various degrees
of perfection in the details of the art of stinging.