HEMIPTERA, OR BUGS—ANOPLURA 532
NOTES AND CORRIGENDA TO VOLUME VI. AND TO INSECTA OF VOLUME V. 602
INDEX 603
{vii}SCHEME OF THE CLASSIFICATION ADOPTED IN THIS BOOK
Order. Sub-order, Family. Sub-Family Group.
Division, or Tribe.
or Series.
HYMENOPTERA (_continued from Vol. V_).
PETIOLATA. (_continued from Vol. V_).
TUBULIFERA (p. 1)
CHRYSIDIDAE (p. 1).
ACULEATA (p. 4)
_ANTHOPHILA_ (p. 10)
APIDAE (p. 10)
Archiapides (p. 21).
Obtusilingues (p. 22).
Andrenides (p. 23).
Denudatae (p. 29).
Scopulipedes (p. 32).
Dasygastres (p. 35).
Sociales (p. 53).
_DIPLOPTERA_ (p. 71)
EUMENIDAE (p. 72).
VESPIDAE (p. 78).
MASARIDAE (p. 88).
_FOSSORES_ (p. 90)
SCOLIIDAE (p. 94)
Mutillides (p. 94).
Thynnides (p. 96).
Scoliides (p. 97).
Sapygides (p. 99).
Rhopalosomides (p. 100).
POMPILIDAE (p. 101).
SPHEGIDAE (p. 107)
Sphegides (p. 107).
Ampulicides (p. 114).
Larrides (p. 116).
Trypoxylonides (p. 118).
Astatides (p. 119).
Bembecides (p. 119).
Nyssonides (p. 123).
Philanthides (p. 124).
Mimesides (p. 127).
Crabronides (p. 128).
_HETEROGYNA_ (p. 131)
FORMICIDAE (p. 131)
Camponotides (p. 144).
Dolichoderides (p. 157).
Myrmicides (p. 158)
Myrmicini (p. 159).
Attini (p. 165).
Pseudomyrmini (p. 168).
Cryptocerini (p. 169).
Ponerides (p. 170).
Dorylides (p. 174)
Ecitonini (p. 175).
Dorylini (p. 177).
Amblyoponides (p. 180).
Order. Sub-Order, Family. Sub-Family or
Division, Tribe.
or Series.
COLEOPTERA (p. 184)
LAMELLICORNIA (p. 190)
PASSALIDAE (p. 192).
LUCANIDAE (p. 193).
SCARABAEIDAE (p. 194)
Coprides (p. 195).
Melolonthides (p. 198).
Rutelides (p. 198).
Dynastides (p. 199).
Cetoniides (p. 199).
ADEPHAGA OR CARABOIDEA (p. 200)
CICINDELIDAE (p. 201).
CARABIDAE (p. 204)
Carabides (p. 206).
Harpalides (p. 206).
Pseudomorphides (p. 206).
Mormolycides (p. 206).
AMPHIZOIDAE (p. 207).
PELOBIIDAE (p. 207).
HALIPLIDAE (p. 209).
DYTISCIDAE (p. 210).
POLYMORPHA (p. 213)
PAUSSIDAE (p. 213).
GYRINIDAE (p. 215).
HYDROPHILIDAE (p. 216).
PLATYPSYLLIDAE (p. 219).
LEPTINIDAE (p. 220).
SILPHIDAE (p. 221).
SCYDMAENIDAE (p. 223).
GNOSTIDAE (p. 223).
PSELAPHIDAE (p. 223).
STAPHYLINIDAE (p. 224).
SPHAERIIDAE (p. 227).
TRICHOPTERYGIDAE (p. 227).
HYDROSCAPHIDAE (p. 228).
CORYLOPHIDAE (p. 228).
SCAPHIDIIDAE (p. 229).
SYNTELIIDAE (p. 229).
HISTERIDAE (p. 230).
PHALACRIDAE (p. 231).
NITIDULIDAE (p. 231).
TROGOSITIDAE (p. 232).
COLYDIIDAE (p. 233).
RHYSODIDAE (p. 234).
CUCUJIDAE (p. 234).
CRYPTOPHAGIDAE (p. 235).
HELOTIDAE (p. 235).
THORICTIDAE (p. 236).
EROTYLIDAE (p. 236).
MYCETOPHAGIDAE (p. 237).
COCCINELLIDAE (p. 237).
ENDOMYCHIDAE (p. 239).
MYCETAEIDAE (p. 239).
LATRIDIIDAE (p. 240).
ADIMERIDAE (p. 240).
DERMESTIDAE (p. 241).
BYRRHIDAE (p. 242).
CYATHOCERIDAE (p. 243).
GEORYSSIDAE (p. 243).
HETEROCERIDAE (p. 243).
PARNIDAE (p. 243).
DERODONTIDAE (p. 244).
CIOIDAE (p. 245).
SPHINDIDAE (p. 245).
BOSTRICHIDAE (p. 246).
PTINIDAE (p. 246)
Ptinides (p. 246).
Anobiides (p. 246).
MALACODERMIDAE (p. 248)
Lycides (p. 248).
Drilides (p. 248).
Lampyrides (p. 248).
Telephorides (p. 248).
MELYRIDAE (p. 252).
CLERIDAE (p. 253).
LYMEXYLONIDAE (p. 254).
DASCILLIDAE (p. 255).
RHIPICERIDAE (p. 256).
ELATERIDAE (p. 256)
Throscides (p. 260).
Eucnemides (p. 260).
Elaterides (p. 260).
Cebrionides (p. 260).
Perothopides (p. 260).
Cerophytides (p. 260).
BUPRESTIDAE (p. 261).
HETEROMERA (p. 262)
TENEBRIONIDAE (p. 263).
CISTELIDAE (p. 264).
LAGRIIDAE (p. 264).
OTHNIIDAE (p. 265).
AEGIALITIDAE (p. 265).
MONOMMIDAE (p. 265).
NILIONIDAE (p. 265).
MELANDRYIDAE (p. 265).
PYTHIDAE (p. 265).
PYROCHROIDAE (p. 266).
ANTHICIDAE (p. 266).
OEDEMERIDAE (p. 266).
MORDELLIDAE (p. 267).
CANTHARIDAE (p. 269).
TRICTENOTOMIDAE (p. 275).
PHYTOPHAGA (p. 276)
BRUCHIDAE (p. 276)
CHRYSOMELIDAE (p. 278)
Eupoda (p. 280).
Camptosomes (p. 281).
Cyclica (p. 282).
Cryptostomes (p. 282).
CERAMBYCIDAE (p. 285)
Prionides (p. 287).
Cerambycides (p. 287).
Lamiides (p. 287).
RHYNCHOPHORA (p. 288)
ANTHRIBIDAE (p. 290).
CURCULIONIDAE (p. 290).
SCOLYTIDAE (p. 294).
BRENTHIDAE (p. 295).
AGLYCYDERIDAE (p. 297).
PROTORHINIDAE (p. 298).
STREPSIPTERA (p. 298)
STYLOPIDAE (p. 298).
LEPIDOPTERA (p. 304)
RHOPALOCERA (p. 341)
NYMPHALIDAE (p. 343)
Danaides (p. 344).
Ithomiides (p. 346).
Satyrides (p. 347).
Morphides (p. 348).
Brassolides (p. 349).
Acraeides (p. 350).
Heliconiides (p. 351).
Nymphalides (p. 352).
ERYCINIDAE (p. 354)
Erycinides (p. 355).
Libytheides (p. 355).
LYCAENIDAE (p. 356).
PIERIDAE (p. 357).
PAPILIONIDAE (p. 359).
HESPERIIDAE (p. 363).
HETEROCERA (p. 366)
CASTNIIDAE (p. 371).
NEOCASTNIIDAE (p. 372).
SATURNIIDAE (p. 372).
BRAHMAEIDAE (p. 374).
CERATOCAMPIDAE (p. 375).
BOMBYCIDAE (p. 375).
EUPTEROTIDAE (p. 376).
PEROPHORIDAE (p. 377).
SPHINGIDAE (p. 380).
COCYTIIDAE (p. 382).
NOTODONTIDAE (p. 383).
CYMATOPHORIDAE (p. 386).
SESIIDAE (p. 386).
TINAEGERIIDAE (p. 387).
SYNTOMIDAE (p. 388).
ZYGAENIDAE (p. 390).
HIMANTOPTERIDAE (p. 392).
HETEROGYNIDAE (p. 392).
PSYCHIDAE (p. 392).
COSSIDAE (p. 395).
ARBELIDAE (p. 396).
CHRYSOPOLOMIDAE (p. 396).
HEPIALIDAE (p. 396).
CALLIDULIDAE (p. 400).
DREPANIDAE (p. 400).
LIMACODIDAE (p. 401).
MEGALOPYOGIDAE (p. 404).
THYRIDIDAE (p. 404).
LASIOCAMPIDAE (p. 405).
ENDROMIDAE (p. 406).
PTEROTHYSANIDAE (p. 406).
LYMANTRIIDAE (p. 406).
HYPSIDAE (p. 408).
ARCTIIDAE (p. 408).
AGARISTIDAE (p. 410).
GEOMETRIDAE (p. 411).
NOCTUIDAE (p. 414).
EPICOPEIIDAE (p. 418).
URANIIDAE (p. 419).
EPIPLEMIDAE (p. 420).
PYRALIDAE (p. 420).
PTEROPHORIDAE (p. 426).
ALUCITIDAE (p. 426).
TORTRICIDAE (p. 427).
TINEIDAE (p. 428).
ERIOCEPHALIDAE (p. 433).
MICROPTERYGIDAE (p. 435).
DIPTERA (p. 438)
ORTHORRHAPHA NEMOCERA (p. 455)
CECIDOMYIIDAE (p. 458).
MYCETOPHILIDAE (p. 462).
BLEPHAROCERIDAE (p. 464).
CULICIDAE (p. 466).
CHIRONOMIDAE (p. 468).
ORPHNEPHILIDAE (p. 470).
PSYCHODIDAE (p. 470).
DIXIDAE (p. 471).
TIPULIDAE (p. 471)
Ptychopterinae (p. 472).
Limnobiinae (p. 473).
Tipulinae (p. 475).
BIBIONIDAE (p. 475).
SIMULIIDAE (p. 477).
RHYPHIDAE (p. 478).
ORTHORRHAPHA BRACHYCERA (pp. 455, 478)
STRATIOMYIDAE (p. 478).
LEPTIDAE (p. 479).
TABANIDAE (p. 481).
ACANTHOMERIDAE (p. 483).
THEREVIDAE (p. 484).
SCENOPINIDAE (p. 484).
NEMESTRINIDAE (p. 484).
BOMBYLIIDAE (p. 485).
ACROCERIDAE (p. 489).
LONCHOPTERIDAE (p. 490).
MYDAIDAE (p. 491).
ASILIDAE (p. 491).
APIOCERIDAE (p. 492).
EMPIDAE (p. 492).
DOLICHOPIDAE (p. 493).
CYCLORRHAPHA ASCIZA (pp. 455, 494)
PHORIDAE (p. 494).
PLATYPEZIDAE (p. 496).
PIPUNCULIDAE (p. 496).
CONOPIDAE (p. 497).
SYRPHIDAE (p. 498).
CYCLORRHAPHA SCHIZOPHORA (pp. 456, 503)
MUSCIDAE ACALYPTRATAE (p. 503).
ANTHOMYIIDAE (p. 506).
TACHINIDAE (p. 507).
DEXIIDAE (p. 510).
SARCOPHAGIDAE (p. 510).
MUSCIDAE (p. 511).
OESTRIDAE (p. 514).
PUPIPARA (pp. 456, 517)
HIPPOBOSCIDAE (p. 518).
BRAULIDAE (p. 520).
STREBLIDAE (p. 521).
NYCTERIBIIDAE (p. 521).
APHANIPTERA (pp. 456, 522)
PULICIDAE (p. 522).
THYSANOPTERA (p. 526)
TEREBRANTIA (p. 531).
TUBULIFERA (p. 531).
Order. Sub-Order. Series. Family.
HEMIPTERA (p. 532)
HETEROPTERA (pp. 543, 544)
GYMNOCERATA (p. 544)
PENTATOMIDAE (p. 545).
COREIDAE (p. 546).
BERYTIDAE (p. 548).
LYGAEIDAE (p. 548).
PYRRHOCORIDAE (p. 549).
TINGIDAE (p. 549).
ARADIDAE (p. 550).
HEBRIDAE (p. 551).
HYDROMETRIDAE (p. 551).
HENICOCEPHALIDAE (p. 554).
PHYMATIDAE (p. 554).
REDUVIIDAE (p. 555).
AËPOPHILIDAE (p. 559).
CERATOCOMBIDAE (p. 559).
CIMICIDAE (p. 559).
ANTHOCORIDAE (p. 560).
POLYCTENIDAE (p. 560).
CAPSIDAE (p. 561).
SALDIDAE (p. 562).
CRYPTOCERATA (p. 562)
GALGULIDAE (p. 562).
NEPIDAE (p. 563).
NAUCORIDAE (p. 565).
BELOSTOMIDAE (p. 565).
NOTONECTIDAE (p. 567).
CORIXIDAE (p. 567).
HOMOPTERA (pp. 543, 568)
TRIMERA (p. 544)
CICADIDAE (p. 568).
FULGORIDAE (p. 574).
MEMBRACIDAE (p. 576).
CERCOPIDAE (p. 577).
JASSIDAE (p. 578).
DIMERA (p. 544)
PSYLLIDAE (p. 578).
APHIDAE (p. 581).
ALEURODIDAE (p. 591).
MONOMERA (p. 544)
COCCIDAE (p. 592).
ANOPLURA (p. 599)
PEDICULIDAE (p. 599).
{1}CHAPTER I
HYMENOPTERA PETIOLATA _CONTINUED_
SERIES 2. TUBULIFERA OR CHRYSIDIDAE—SERIES 3. ACULEATA—GENERAL—
CLASSIFICATION—DIVISION I. ANTHOPHILA OR BEES
The First Series—Parasitica—of the Sub-Order Hymenoptera Petiolata was
discussed in the previous volume. We now pass to the Second Series.
SERIES 2. HYMENOPTERA TUBULIFERA.
_Trochanters undivided; the hind-body consisting of from three to five
visible segments; the female with an ovipositor, usually retracted,
transversely segmented, enveloping a fine, pointed style. The larvae
usually live in the cells of other Hymenoptera._
The Tubulifera form but a small group in comparison with Parasitica and
Aculeata, the other two Series of the Sub-Order. Though of parasitic
habits, they do not appear to be closely allied to any of the families of
Hymenoptera Parasitica, though M. du Buysson suggests that they have some
affinity with Proctotrypidae; their morphology and classification have
been, however, but little discussed, and have not been the subject of any
profound investigation. At present it is only necessary to recognise one
family, viz. Chrysididae or Ruby-wasps.[1] These Insects are usually of
glowing, metallic colours, with a very hard, coarsely-sculptured
integument. Their antennae are abruptly elbowed, the joints not being
numerous, usually about thirteen, and frequently so {2}connected that it is
not easy to count them. The abdomen is, in the great majority, of very
peculiar construction, and allows the Insect to curl it completely under
the anterior parts, so as to roll up into a little ball; the dorsal plates
are very strongly arched, and seen from beneath form a free edge, while the
ventral plates are of less hard consistence, and are connected with the
dorsal plates at some distance from the free edge, so that the abdomen
appears concave beneath. In the anomalous genus _Cleptes_ the abdomen is,
however, similar in form to that of the Aculeate Hymenoptera, and has four
or five visible segments, instead of the three or four that are all that
can be seen in the normal Chrysididae. The larvae of the Ruby-flies have
the same number of segments as other Hymenoptera Petiolata. The difference
in this respect of the perfect Chrysididae from other Petiolata is due to a
greater number of the terminal segments being indrawn so as to form the
tube, or telescope-like structure from which the series obtains its name.
This tube is shown partially extruded in Fig. 1; when fully thrust out it
is seen to be segmented, and three or four segments may be distinguished.
The ovipositor proper is concealed within this tube; it appears to be of
the nature of an imperfect sting; there being a very sharply pointed style,
and a pair of enveloping sheaths; the style really consists of a
trough-like plate and two fine rods or spiculae. There are no poison
glands, except in _Cleptes_, which form appears to come very near to the
Aculeate series. Some of the Chrysididae on occasions use the ovipositor as
a sting, though it is only capable of inflicting a very minute and almost
innocuous wound.
[Illustration: Fig. 1.—_Chrysis ignita_, ♀. England.]
Although none of the Ruby-flies attain a large size, they are usually very
conspicuous on account of their gaudy or brilliant colours. They are
amongst the most restless and rapid of Insects; {3}they love the hot
sunshine, and are difficult of capture. Though not anywhere numerous in
species, they are found in most parts of the world. In Britain we have
about twenty species. They usually frequent old wood or masonry, in which
the nests of Aculeate Hymenoptera exist, or fly rapidly to and fro about
the banks of earth where bees nest. Dr. Chapman has observed the habits of
some of our British species.[2] He noticed _Chrysis ignita_ flying about
the cell of _Odynerus parietum_, a solitary wasp that provisions its nest
with caterpillars; in this cell the _Chrysis_ deposited an egg, and in less
than an hour the wasp had sealed the cell. Two days afterwards this was
opened and was found to contain a larva of _Chrysis_ a quarter of an inch
long, as well as the Lepidopterous larvae stored up by the wasp, but there
was no trace of egg or young of the wasp. Six days after the egg was laid
the _Chrysis_ had eaten all the food and was full-grown, having moulted
three or four times. Afterwards it formed a cocoon in which to complete its
metamorphosis. It is, however, more usual for the species of _Chrysis_ to
live on the larva of the wasp and not on the food; indeed, it has recently
been positively stated that _Chrysis_ never eats the food in the wasp's
cell, but there is no ground whatever for rejecting the evidence of so
careful an observer as Dr. Chapman. According to M. du Buysson the larva of
_Chrysis_ will not eat the lepidopterous larvae, but will die in their
midst if the _Odynerus_ larva does not develop; but this observation
probably relates only to such species as habitually live on _Odynerus_
itself. The mother-wasp of _Chrysis bidentata_ searches for a cell of
_Odynerus spinipes_ that has not been properly closed, and that contains a
full-grown larva of that wasp enclosed in its cocoon. Having succeeded in
its search the _Chrysis_ deposits several eggs—from six to ten; for some
reason that is not apparent all but one of these eggs fail to produce
young; in two or three days this one hatches, the others shrivelling up.
The young _Chrysis_ larva seizes with its mouth a fold of the skin of the
helpless larva of the _Odynerus_, and sucks it without inflicting any
visible wound. In about eleven days the _Chrysis_ has changed its skin four
times, has consumed all the larva and is full-fed; it spins its own cocoon
inside that of its victim, and remains therein till the following spring,
when it changes to a pupa, and in less than three weeks {4}thereafter
emerges a perfect _Chrysis_ of the most brilliant colour, and if it be a
female indefatigable in activity. It is remarkable that the larva of
_Chrysis_ is so much like that of _Odynerus_ that the two can only be
distinguished externally by the colour, the _Odynerus_ being yellow and the
_Chrysis_ white; but this is only one of the many cases in which host and
parasite are extremely similar to the eye. _Chrysis shanghaiensis_ has been
reared from the cocoons of a Lepidopterous Insect—_Monema flavescens_,
family Limacodidae—and it has been presumed that it eats the larva therein
contained. All other Chrysids, so far as known, live at the expense of
Hymenoptera (usually, as we have seen, actually consuming their bodies),
and it is not impossible that _C. shanghaiensis_ really lives on a
Hymenopterous parasite in the cocoon of the Lepidopteron.
_Parnopes carnea_ frequents the nests of _Bembex rostrata_, a solitary wasp
that has the unusual habit of bringing from time to time a supply of food
to its young larva; for this purpose it has to open the nest in which its
young is enclosed, and the _Parnopes_ takes advantage of this habit by
entering the cell and depositing there an egg which produces a larva that
devours that of the _Bembex_. The species of the anomalous genus _Cleptes_
live, it is believed, at the expense of Tenthredinidae, and in all
probability oviposit in their cocoons which are placed in the earth.
SERIES 3. HYMENOPTERA ACULEATA.
_The females (whether workers or true females) provided with a sting:
trochanters usually undivided (monotrochous). Usually the antennae of the
males with thirteen, of the females with twelve, joints (exceptions in
ants numerous)._
These characters only define this series in a very unsatisfactory manner,
as no means of distinguishing the "sting" from the homologous structures
found in Tubulifera, and in the Proctotrypid division of Hymenoptera
Parasitica, have been pointed out. As the structure of the trochanters is
subject to numerous exceptions, the classification at present existing is
an arbitrary one. It would probably be more satisfactory to separate the
Proctotrypidae (or a considerable part thereof) from the Parasitica, and
unite them with the Tubulifera and Aculeata in a great series,
characterised by the fact that the ovipositor is {5}withdrawn into the body
in a direct manner so as to be entirely internal, whereas in the Parasitica
it is not withdrawn in this manner, but remains truly an external organ,
though in numerous cases concealed by a process of torsion of the terminal
segments. If this were done it might be found possible to divide the great
group thus formed into two divisions characterised by the fact that the
ovipositor in one retains its function, the egg passing through it
(Proctotrypidae and Tubulifera), while in the other the organ in question
serves as a weapon of offence and defence, and does not act as a true
ovipositor, the egg escaping at its base. It would, however, be premature
to adopt so revolutionary a course until the comparative anatomy of the
organs concerned shall have received a much greater share of attention; a
detailed scrutiny of Prototrypidae being particularly desired.
[Illustration: Fig. 2.—Diagram of upper surface of _Priocnemis affinis_ ♀,
Pompilidae. _o_, ocelli; _B^1_, pronotum; _B^2_, mesonotum; _B^3_,
scutellum of mesonotum; _B^4_, post-scutellum or middle part of metanotum;
_B^5_, propodeum or median segment (see vol. v. p. 491); _B^6_, combing
hairs, pecten, of front foot: _C^1_, first segment of abdomen, here not
forming a pedicel or stalk: _D^1_, coxa; _D^2_, trochanter; _D^3_, femur;
_D^6_, calcaria or spurs of hind leg: 1 to 15, nervures of wings, viz. 1,
costal; 2, post-costal; 3, median; 4, posterior; 5, stigma; 6, marginal; 7,
upper basal; 8, lower basal; 9, 9, cubital; 10, the three sub-marginal; 11,
first recurrent; 12, second recurrent; 13, anterior of hind wing; 14,
median; 15, posterior: I to XI, the cells, viz. I, upper basal; II, lower
basal; III, marginal; IV, V, VI, first, second and third sub-marginal; VII,
first discoidal; VIII, third discoidal; IX, second discoidal; X, first
apical; XI, second apical.]
We have dealt with the external anatomy of Hymenoptera in {6}Vol. V.; so
that here it is only necessary to give a diagram to explain the terms used
in the descriptions of the families and sub-families of Aculeata, and to
discuss briefly their characteristic structures.
[Illustration: Fig. 3—Sting of bee. A, One of the needles separated; _a_,
the barbed point; _b_, piston; _c_, arm. B, Transverse section of the
sting: _dd_, the two needles; _e_, bead for guiding the needles; _f_,
director; _g_, channel of poison. (After Carlet.)]
The Sting of the bee has been described in detail by Kraepelin, Sollmann,
Carlet[3] and others. It is an extremely perfect mechanical arrangement.
The sting itself—independent of the sheaths and adjuncts—consists of three
elongate pieces, one of them a gouge-like director, the other two pointed
and barbed needles; the director is provided with a bead for each of the
needles to run on, these latter having a corresponding groove; the entrance
to the groove is narrower than its subsequent diameter, so that the needles
play up and down on the director with facility, but cannot be dragged away
from it; each needle is provided with an arm at the base to which are
attached the muscles for its movement. This simple manner of describing the
mechanical arrangement is, however, incomplete, inasmuch as it includes no
account of the means by which the poison is conveyed. This is done by a
very complex set of modifications of all the parts; firstly, the director
is enlarged at the anterior part to form a chamber, through which the
needles play; the needles are each provided with a projecting piece, which,
as the needle moves, plays in the chamber of the director, and forces
downwards any liquid that may be therein; the poison-glands open into the
chamber, and the projections on the needles, acting after the manner of a
piston, carry the poison before them. The needles are so arranged on {7}the
director that they enclose between themselves and it a space that forms the
channel along which the poison flows, as it is carried forwards by the
movement of the pistons attached to the needles. If the needles be thrust
into an object quite as far as, or beyond, the point of the director much
poison may be introduced into a wound, as the barbs are provided with small
orifices placed one above the other, while if this be not the case much of
the liquid will flow on the outside of the object.
According to Carlet the poison of the bee is formed by the mixture of the
secretions of two glands, one of which is acid and the other alkaline; it
is very deadly in its effects on other Insects. We shall see, however, that
the Fossorial Hymenoptera, which catch and sting living prey for their
young, frequently do not kill but only stupefy it, and Carlet states that
in this group the alkaline gland is absent or atrophied, so that the poison
consists only of the acid; it is thus, he thinks, deprived of its lethal
power. Moreover, in the Fossoria the needles are destitute of barbs, so
that the sting does not remain in the wound. Bordas, however, states[4]
that in all the numerous Hymenoptera he has examined, both acid and
alkaline glands exist, but exhibit considerable differences of form in the
various groups. He gives no explanation of the variety of effects of the
poison of different Aculeata.
The larvae (for figure of larva of _Bombus_, see Vol. V. p. 488) are,
without known exception, legless grubs, of soft consistence, living
entirely under cover, being protected either in cells, or, in the case of
social Hymenoptera, in the abodes of the parents. The larvae of Ants and
fossorial Hymenoptera have the anterior parts of the body long and narrow
and abruptly flexed, so that their heads hang down in a helpless manner.
All the larvae of Aculeates, so far as known, are remarkable from the fact
that the posterior part of the alimentary canal does not connect with the
stomach till the larval instar is more or less advanced; hence the food
amongst which they live cannot be sullied by faecal matter. The pupa is
invariably soft, and assumes gradually the colour of the perfect Insect.
Almost nothing is known as to the intimate details of the metamorphosis,
and very little as to the changes of external form. According to Packard a
period intervenes between the stadium of the full-grown larva and that of
the pupa, in which a series of changes he speaks of as semi-pupal {8}are
passed through; these, however, have not been followed out in the case of
any individual, and it is not possible to form any final idea about them,
but it seems probable that they are largely changes of external shape, in
conformity with the great changes going on in the internal organs. Owing to
the fragmentary nature of observations, much obscurity and difference of
opinion have existed as to the metamorphosis of Aculeate Hymenoptera. Sir
S. Saunders gives the following statement as to the larva of a wasp of the
genus _Psiliglossa_,[5] just before it assumes the pupal form: "The
respective segments, which are very distinctly indicated, may be defined as
follows:—The five anterior, including the head, are compactly welded
together, and incapable of separate action in the pseudo-pupa state; the
third, fourth, and fifth bearing a spiracle on either side. The thoracical
region terminating here, the two anterior segments are assignable to the
development of the imago head, as pointed out by Ratzeburg." This inference
is not, however, correct. We have seen that in the perfect Insect of
Petiolate Hymenoptera the first abdominal segment is fixed to the thorax,
and Saunders' statement is interesting as showing that this assignment of
parts already exists in the larva, but it in no way proves that the head of
the imago is formed from the thorax of the larva. It has been stated that
the larvae of the Aculeata have a different number of segments according to
the sex, but this also is incorrect. The difference that exists in the
perfect Insects in this respect is due to the withdrawal of the terminal
three segments to the interior in the female, and of two only in the male.
The larva consists of fourteen segments, and we find this number
distributed in the female perfect Insect as follows: one constitutes the
head, four segments the thorax and propodeum, followed by six external
segments of the restricted abdomen, and three for the internal structures
of the abdomen. This agrees with Forel's statement that in the ants the
sting is placed in a chamber formed by three segments.
The development of the sting of the common bee has been studied by
Dewitz.[6] It takes place in the last larval stage. Although nothing of the
organ is visible externally in the adult larva, yet if such a larva be
placed in spirit, there can be seen within the skin certain small
appendages on the ventral surface of the penultimate and antepenultimate
abdominal segments {9}(Fig. 4, A) placed two on the one, four on the other;
these are the rudiments of the sting. In the course of development the
terminal three segments are taken into the body, and the external pair of
the appendages of the twelfth body segment (the ninth abdominal) become the
sheaths of the sting, and the middle pair become the director; the pair of
appendages on the eleventh segment give rise to the needles or spiculae.
The sting-rudiments at an earlier stage (Fig. 4, C) are masses of
hypodermis connected with tracheae; there is then but one pair on the
twelfth segment, and this pair coalesce to form a single mass; the
rudiments of the pair that form the director are differentiated secondarily
from the primary pair of these masses of hypodermis. A good deal of
discussion has taken place as to whether the component parts of the
sting—gonapophyses—are to be considered as modifications of abdominal
extremities (_i.e._ abdominal legs such as exist in Myriapods). Heymons is
of opinion that this is not the case, but that the leg-rudiments and
gonapophysal rudiments are quite distinct.[7] The origin of the sting of
Hymenoptera (and of the ovipositor of parasitic Hymenoptera) is very
similar to that of the ovipositor of _Locusta_ (Vol. V. p. 315 of this
work), but there is much difference in the history of the development of
the rudiments.
[Illustration: Fig. 4—Development of sting of the bee: A and C, ventral; B,
side view. A, End of abdomen of adult larva: _a_, _b_, _c_, _d_, the last
four segments, _c_ being the eleventh body segment, 11; _b_ bearing two
pairs, and _c_ one pair, of rudiments. B, Tip of abdomen of adult bee: 9,
the ninth, _d_, the tenth body segment. C, Rudiments in the early condition
as seen within the body: _c_, first pair; _b_, the second pair not yet
divided into two pairs; _b″_, _c′_, commencement of external growths from
the internal projections. (After Dewitz.)]
Dewitz has also traced the development of the thoracic appendages in
Hymenoptera.[8] Although no legs are visible in the adult larva, they
really arise very early in the larval life from masses of hypodermis, and
grow in the interior of the body, so that when the larva is adult the legs
exist in a segmented though rudimentary condition in the interior of the
body. Dewitz's study of the wing-development is less complete.
{10}Four primary divisions of Aculeates are generally recognised, viz.
Anthophila (Bees), Diploptera (Wasps), Fossores (Solitary Wasps),
Heterogyna (Ants). Though apparently they are natural, it is impossible to
define them by characters that are without some exceptions, especially in
the case of the males. Ashmead has recently proposed[9] to divide the
Fossores; thus making five divisions as follows:—
Body with more or less of the hairs on it plumose 1. Anthophila.
Hairs of body not plumose.
Pronotum not reaching back to tegulae 2. Entomophila
[= Fossores part].
Pronotum reaching back to tegulae.
Petiole (articulating segment of abdomen) simple without
scales or nodes.
Front wings in repose with a fold making them narrow
3. Diploptera.
Front wings not folded 4. Fossores [part].
Petiole with a scale or node (an irregular elevation
on the upper side) 5. Heterogyna.
We shall here follow the usual method of treating all the fossorial wasps
as forming a single group, uniting Ashmead's Entomophila and Fossores, as
we think their separation is only valid for the purposes of a table; the
Pompilidae placed by the American savant in Fossores being as much allied
to Entomophila as they are to the other Fossores with which Ashmead
associates them.
DIVISION I. ANTHOPHILA OR APIDAE—BEES.
_Some of the hairs of the body plumose; parts of the mouth elongated,
sometimes to a great extent, so as to form a protrusible apparatus,
usually tubular with a very flexible tip. Basal joint of hind foot
elongate. No wingless adult forms; in some cases societies are formed,
and then barren females called workers exist in great numbers, and carry
on the industrial operations of the community. Food always derived from
the vegetable kingdom, or from other Bees._
There are about 150 genera and 1500 species of bees at present known. Some
call the division Mellifera instead of Anthophila. The term Apidae is used
by some authorities to denote all the bees, while others limit this term to
one of the families {11}or sub-divisions. The bees are, as a rule,
distinguished from other Hymenoptera by the hairs, by the great development
of the mouth parts to form a proboscis (usually, but not correctly, called
tongue), and by the modification of the hind-legs; but these distinctive
characters are in some of the species exhibited in so minor a degree of
perfection that it is not easy to recognise these primitive forms as
Anthophila. A few general remarks on the three points mentioned will enable
the student to better appreciate the importance of certain points we shall
subsequently deal with.
[Illustration: Fig. 5—Hairs of Bees: A, simple hair from abdomen of
_Osmia_; B, spiral hair from abdomen of _Megachile_; C, plumose hair from
thorax of _Megachile_; D, from thorax of _Andrena dorsata_; E, from thorax
of _Prosopis_.]
The bees are, as a rule, much more covered with hair than any other of the
Hymenoptera. Saunders[10] states that he has examined the structure of the
hairs in all the genera of British Aculeata, and that in none but the
Anthophila do branched and plumose hairs occur. The function of this kind
of hairs is unknown; Saunders suggests[10] that they may be instrumental in
the gathering of pollen, but they occur in the parasitic bees as well as in
the males, neither of which gather pollen. The variety of the positions
they occupy on the body seems to offer but little support to the
suggestion. Not all the hairs of the bee's body are plumose, some are
simple, as shown in Fig. 5, A, and this is specially the case with the
hairs that are placed at the edges of the dilated plates for carrying
pollen. In some forms there is an extensive system of simple hairs all over
the body, and the "feathers" are distributed between these; and we do not
see any reason for assuming that the feathered are superior to the simple
hairs for gathering and carrying pollen. Some bees, _e.g._ _Prosopis_,
_Ceratina_, have very little hair on the body, but nevertheless some
plumose hairs are always present even though they be very short.
{12}[Illustration: Fig. 6—A, Worker of the honey-bee (_Apis mellifica_),
with pollen plates laden; B, basal portions of a middle-leg (trochanter
with part of coxa and of femur) with plumose hairs and grains of pollen; C,
one hair bearing pollen-grains.]
The hind-legs of bees are very largely used in the industrial occupations
of these indefatigable creatures; one of their chief functions in the
female being to act as receptacles for carrying pollen to the nest: they
exhibit, however, considerable diversity. The parts most modified are the
tibia and the first joint of the hind-foot. Pollen is carried by other
parts of the body in many bees, and even the hind-leg itself is used in
different ways for the purpose: sometimes the outer face of the tibia is
highly polished and its margins surrounded by hair, in which case pollen
plates are said to exist (Fig. 6, A); sometimes the first joint of the
tarsus is analogous to the tibia both in structure and function; in other
cases the hind-legs are thick and densely covered with hair that retains
the pollen between the separate hairs. In this case the pollen is carried
home in a dry state, while, in the species with pollen plates, the pollen
is made into a mass of a clay-like consistence.[11] The legs also assist in
arranging the pollen on the other parts of the body. The males do not carry
pollen, and though their hind-legs are also highly modified, yet the
modifications do not agree with those of the female, and their functions
are in all probability sexual. The parasitic bees also do not carry pollen,
and exhibit another series of structures. The most interesting case in this
series of modifications is that found in the genus _Apis_, where the
hind-leg of male, female, and worker are all different (Fig. 25); the limb
in the worker being highly modified for industrial purposes. This case has
been frequently referred to, in consequence of the difficulty that exists
in connection with its heredity, for the {13}structure exists in neither of
the parents. It is, in fact, a case of a very special adaptation appearing
in the majority of the individuals of each generation, though nothing of
the sort occurs in either parent.
The proboscis of the bee[12] is a very complex organ, and in its extremely
developed forms exhibits a complication of details and a delicacy of
structure that elicit the admiration of all who study it. In the lower
bees, however, especially in _Prosopis_, it exists in a comparatively
simple form (Fig. 9, B, C), that differs but little from what is seen in
some Vespidae or Fossores. The upper lip and the mandibles do not take any
part in the formation of the bee's proboscis, which is consequently
entirely made up from the lower lip and the maxillae, the former of these
two organs exhibiting the greatest modifications. The proboscis is situate
on the lower part of the head, and in repose is not visible; a portion, and
that by no means an inconsiderable one, of its modifications being for the
purpose of its withdrawal and protection when not in use. For this object
the under side of the head is provided with a very deep groove, in which
the whole organ is, in bees with a short proboscis, withdrawn; in the
Apidae with a long proboscis this groove also exists, and the basal part of
the proboscis is buried in it during repose, while the other parts of the
elongate organ are doubled on the basal part, so that they extend backwards
under the body, and the front end or tip of the tongue is, when in repose,
its most posterior part.
For the extrusion of the proboscis there exists a special apparatus that
comes into play after the mandibles are unlocked and the labrum lifted.
This extensive apparatus cannot be satisfactorily illustrated by a drawing,
as the parts composing it are placed in different planes; but it may be
described by saying that the cardo, or basal hinge of the maxilla, changes
from an oblique to a vertical position, and thrusts the base of the
proboscis out of the groove. The maxillae form the outer sheath of the
proboscis, the lower lip its medial part (see Figs. 7 and 9); the base of
the lower lip is attached to the submentum, which rises with the cardo so
that labium and maxillae are lifted together; the co-operation of these two
parts is effected by an angular piece called the lorum, in which the base
of the submentum rests; the submentum is articulated with the mentum in
such a manner that the two can either be placed in planes at a right angle
to one another, or can be brought into one continuous plane, and by this
change of plane the basal part of the tongue can also be thrust forwards.
{14}[Illustration: Fig. 7.—Side view of basal portions of proboscis of
_Bombus_. _a_, Epipharyngeal sclerites; _b_, arrow indicating the position
of the entrance to pharynx, which is concealed by the epipharynx, _c_; _d_,
hypopharyngeal sclerites; _e_, vacant space between the scales of the
maxillae through which the nectar comes: _f_, lobe; _f′_, stipes; _g_,
cardo of maxilla: _h_, encephalic pillar on which the cardo swings; _i_,
angle of junction of lores and submentum lorum; _k_, mentum; _l_, base of
labial palp; _m_, maxillary palp.]
There is considerable variety in the lengths of these parts in different
genera, and the lorum varies in shape in accordance with the length of the
submentum. The lorum is a peculiar piece, and its mechanical adaptations
are very remarkable; usually the base of the submentum rests in the angle
formed by the junction of the two sides of the lorum, but in _Xylocopa_,
where the submentum is unusually short, this part reposes in a groove on
the back of the lorum, this latter having a very broad truncated apex
instead of an angular one; in the condition of repose the apex of the lorum
rests in a notch on the middle of the back of the oral groove, and in some
of the forms with elongate submentum, this depression is transformed into a
deep hole, or even a sort of tunnel, so as to permit the complete stowing
away of the base of the tongue, which would otherwise be prevented by the
long submentum; another function of the lorum appears to be that, as it
extends, its arms have an outward thrust, and so separate the maxillae from
the labium. In addition to these parts there are also four elongate,
slender sclerites that are only brought into view on dissection, and that
no doubt assist in correlating the movements of the parts of the mouth and
{15}hypopharynx; one pair of these strap-like pieces extends backwards from
the two sides of the base of the epipharynx; Huxley called them sclerites
of the oesophagus; a better name would be epipharyngeal sclerites (Fig. 7,
_a_): the other pair pass from the terminations of the epipharyngeal
sclerites, along the front face of the hypopharynx, down to the mentum,
their lower parts being concealed by the stipites of the maxillae; these
are the hypopharyngeal sclerites, and we believe it will prove that they
play a highly important part in deglutition. When the labrum of a bee is
raised and the proboscis depressed, the epipharynx is seen hanging like a
curtain from the roof of the head; this structure plays an important part
in the act of deglutition. The entrance to the pharynx, or commencement of
the alimentary canal, is placed below the base of the epipharynx. As we are
not aware of any good delineations of the basal parts of the proboscis we
give a figure thereof (Fig. 7). The maxillae in the higher bees are
extremely modified so as to form a sheath, and their palpi are minute; in
the lower bees the palpi have the structure usual in mandibulate Insects.
Returning to the consideration of the lower lip, we find that there is
attached to the mentum a pair of elongate organs that extend forwards and
form a tube or sheath, enclosed by the maxillary sheath we have previously
mentioned; these are the greatly modified labial palpi, their distal parts
still retaining the palpar form; and in the lower bees the labial palpi
are, like the maxillary, of the form usual in mandibulate Insects. Between
the labial palps and the central organ of the lip there is attached a pair
of delicate organs, the paraglossae.
There remains for consideration the most remarkable part of the proboscis,
the long, delicate, hairy organ which the bee thrusts out from the tip of
the shining tube formed by the labial palps and the maxillae, described
above, and which looks like a prolongation of the mentum. This organ is
variously called ligula, lingua, or tongue.[13] We prefer the first of
these names.
According to Breithaupt and Cheshire the structure of the ligula is highly
remarkable; it is a tube (filled with fluid from the body cavity), and with
a groove underneath caused by a large part of the circumference of the tube
being invaginated; the {16}invaginated part can be thrust out by increase
of the pressure of the fluid in the tube. A portion of the wall of the
invaginate part is thickened so as to form a chitinous rod.
This description will suffice for present purposes, as the other parts of
the mouth will be readily recognised by the aid of figure 9, A, B, C. In
the exquisitely endowed South American genus _Euglossa_ (Fig. 18), the
proboscis is somewhat longer than the whole of the body, so that its tip in
repose projects behind the body like a sting.
[Illustration: Fig. 8.—Transverse section of ligula of honey-bee,
diagramatic. A, With the long sac invaginate. B, evaginate: _a_, chitinous
envelope with the bases of the hairs; _b_, rod; _c_, groove of rod; _d_,
lumen due in A to invagination of the rod, in B to its evagination; _n_,
nerve; _tr_, trachea.]
The correct nomenclature of the parts connected with the lower lip is not
definitely settled, authorities not being agreed on several points. The
whole of the proboscis is usually called the tongue; this, however, is
admittedly an erroneous application of this term. The terminal delicate,
elongate, flexible organ is by some called the tongue; but this again is
wrong: the lingua in Insects is the hypopharynx; this part is developed in
a peculiar manner in bees, but as it is not tongue-like in shape, the term
lingua is not suitable for it, and should be dismissed altogether from the
nomenclature of the bee's trophi; it is used at present in two different
senses, both of which are erroneous. We see no objection to describing the
flexible apical portion of the proboscis as the ligula. The lorum is
probably a special part peculiar to the higher bees; according to Saunders
it is not present as a specialised part in some of the primitive forms.[14]
The application of the terms mentum, submentum and hypoglottis is open to
the same doubts that exist with regard to them in so many other
{17}Insects, and we have omitted the term hypoglottis altogether, though
some may think the mentum entitled to that name.
[Illustration: Fig. 9.—A, Proboscis of a "long-tongued" bee, _Anthophora
pilipes_; B, lower, C, upper view of proboscis of an "obtuse-tongued" bee,
_Prosopis pubescens_. _a_, Labrum; _b_, stipes; _c_, palpiger; _d_, scale:
_f_, lobe; _g_, palpus; _h_, cardo, of maxilla: _i_, lorum; _k_, submentum;
_l_, mentum; _m_, labial palp; _n_, paraglossa; _o_, ligula; _p_, tip of
ligula (with "spoon" at tip and some of the hairs more magnified); _q_,
hypopharyngeal sclerites.]
The way in which the proboscis of the bee acts has been very largely
discussed, with special reference to the question as to whether it is a
sucking or a licking action. It is impossible to consider either of these
terms as applicable. The foundation of the action is capillary attraction,
by which, and by slight movements of increase and contraction of the
capacity of various parts, the fluid travels to the cavity in front of the
hypopharynx: here the scales of the maxillae leave a vacant space, (Fig. 7,
_e_) so that a cup or cavity is formed, the fluid in which is within reach
of the tip of the dependent epipharynx (_c_), which hangs down over the
front of the hypopharynx (and is so shaped that its tip covers the cup); it
is between these two parts that the fluid passes to reach the pharynx. It
is no doubt to slight movements of the membranous parts of the hypopharynx
and of the epipharynx that the further progress of the nectar is due, aided
by contraction and expansion of the pharynx, induced by muscles attached to
it. It should be recollected that in addition to the movements of the head
itself, the hypopharynx is constantly changing its dimensions slightly by
the impulses of the fluid of the general body cavity; also that the head
changes its position, {18}and that the proboscis is directed downwards as
well as forwards. Those who wish to pursue this subject should refer to the
works of Breithaupt[15] and Cheshire.
The other external characters of the Bees call for little remark. The
pronotum is never very large or much prolonged in front, and its hind
angles never repose on the tegulae as they do in the wasps,[16] but extend
backwards below the tegulae. The hind body is never narrowed at the base
into an elongate pedicel, as it so frequently is in the Wasps and in the
Fossors; and the propodeum (the posterior part of the thorax) is more
perpendicular and rarely so largely developed as it is in the Fossors; this
last character will as a rule permit a bee to be recognised at a glance
from the fossorial Hymenoptera.
Bees, as every one knows, frequent flowers, and it is usually incorrectly
said that they extract honey. They really gather nectar, swallow it, so
that it goes as far as the crop of their alimentary canal, called in
English the honey-sac, and is regurgitated as honey. Bertrand states that
the nectar when gathered is almost entirely pure saccharose, and that when
regurgitated it is found to consist of dextrose and levulose:[17] this
change appears to be practically the conversion of cane- into grape-sugar.
A small quantity of the products of the salivary glands is added, and this
probably causes the change alluded to; so that honey and nectar are by no
means synonymous. According to Cheshire the glandular matter is added while
the nectar is being sucked, and is passing over the middle parts of the
lower lip, so that the nectar may be honey when swallowed by the bee. In
addition to gathering nectar the female bees are largely occupied in
collecting pollen, which, mixed with honey, is to serve as food for the
colony. Many, if not all, bees eat pollen while collecting it. The mode in
which they accumulate the pollen, and the mechanism of its conveyance from
hair to hair till it reaches the part of the body it must attain in order
to be removed for packing in the cells, is not fully understood, but it
appears to be accomplished by complex correlative actions of various parts;
the head and the front legs scratch up the pollen, the legs move with great
rapidity, and the pollen ultimately reaches its destination. The workers of
the genus _Apis_, and of some other social {19}bees, have the basal joint
of the hind foot specially adapted to deal with pollen (Fig. 25, 2). We
have already mentioned the modifications of the legs used for its
conveyance, and need here only add that numerous bees—the Dasygastres—carry
the pollen by aid of a special and dense clothing of hairs on the underside
of the abdomen.
The buzzing of bees (and other Insects) has been for long a subject of
controversy: some having maintained that it is partially or wholly due to
the vibration of parts connected with the spiracles, while others have
found its cause in the vibrations of the wings. According to the
observations of Pérez and Bellesme,[18] two distinct sounds are to be
distinguished. One, a deep noise, is due to the vibration of the wings, and
is produced whenever a certain rapidity is attained; the other is an acute
sound, and is said to be produced by the vibrations of the walls of the
thorax, to which muscles are attached; this sound is specially evident in
Diptera and Hymenoptera, because the integument is of the right consistence
for vibration. Both of these observers agree that the spiracles are not
concerned in the matter.
The young of bees are invariably reared in cells. These (except in the case
of the parasitical bees) are constructed by the mothers, or by the
transformed females called workers. The solitary bees store the cells with
food, and close up each cell after having laid an egg in it, so that in
these cases each larva consumes a special store previously provided for it.
The social bees do not close the cells in which the larvae are placed, and
the workers act as foster-mothers, feeding the young larvae after the same
fashion as birds feed their nestling young. The food is a mixture of honey
and pollen, the mixing being effected in various ways and proportions
according to the species; the honey seems to be particularly suitable to
the digestive organs of the young larvae, and those bees that make closed
cells, place on the outside of the mass of food a layer more thickly
saturated with honey, and this layer the young grub consumes before
attacking the drier parts of the provisions. The active life of the larva
is quite short, but after the larva is full-grown it usually passes a more
or less prolonged period in a state of quiescence before assuming the pupal
form. The pupa shows the limbs and other parts of the perfect Insect in a
very distinct manner, and the {20}development of the imago takes place
gradually though quickly. Some larvae spin cocoons, others do not.
A very large number of bees are parasitic in their habits, laying an egg,
or sometimes more than one, in the cell of a working bee of some species
other than their own; in such cases the resulting larvae eat and grow more
quickly than the progeny of the host bee, and so cause it to die of
starvation. It has been observed that some of these parasitic larvae, after
eating all the store of food, then devour the larva they have robbed. In
other cases it is possible that the first care of the parasitic larva,
after hatching, is to eat the rival egg.
The taxonomy of bees is in a very unsatisfactory state. The earlier
Hymenopterists were divided into two schools, one of which proposed to
classify the bees according to their habits, while the other adopted an
arrangement depending on the length of the parts of the mouth, the
development of the palpi, and the form and positions of the organs for
carrying pollen. Neither of these arrangements was at all satisfactory, and
some entomologists endeavoured to combine them, the result being a
classification founded partly on habits and partly on certain minor
structural characters. This course has also proved unsatisfactory; this is
especially the case with exotic bees, which have been placed in groups that
are defined by habits, although very little observation has actually been
made on this point. Efforts have recently been made to establish an
improved classification, but as they relate solely to the European bees
they are insufficient for general purposes.
The more important of the groups that have been recognised are—(1) the
Obtusilingues, short-tongued bees, with the tip of the lingua bifid or
broad; (2) Acutilingues, short-tongued bees, with acute tip to the tongue;
these two groups being frequently treated of as forming the Andrenidae.
Coming to the Apidae, or the bees with long and folded tongues, there have
been distinguished (3) Scopulipedes, bees carrying pollen with their feet,
and (4) Dasygastres, those that carry it under the abdomen; some of the
parasitic and other forms have been separated as (5) Denudatae (or
Cuculinae); the Bombi and the more perfectly social bees forming another
group, viz. (6) Sociales. A group Andrenoides, or Panurgides, was also
proposed for certain bees considered to belong to the Apidae though
exhibiting many points of {21}resemblance with the Andrenidae. This
arrangement is by no means satisfactory, but as the tropical bees have been
but little collected, and are only very imperfectly known, it is clear that
we cannot hope for a better classification till collections have been very
much increased and improved. The arrangement adopted in Dalla Torre's
recent valuable catalogue of bees[19] recognises no less than fourteen
primary divisions, but is far from satisfactory.
[Illustration: Fig. 10—_Prosopis signata._ Cambridge. A, Female; B, front
of head of female; C, of male.]
The two genera _Prosopis_ and _Sphecodes_ have been recently formed into a
special family, Archiapidae, by Friese,[20] who, however, admits that the
association is not a natural one. The term should be limited to _Prosopis_
and the genera into which it has been, or shortly will be, divided. The
primitive nature of the members of this genus is exhibited in all the
external characters that are most distinctive of bees; the proboscis (Fig.
9, B, C), is quite short, its ligula being very short, and instead of being
pointed having a concave front margin. The body is almost bare, though
there is some very short feathered plumage. The hind legs are destitute of
modifications for industrial purposes. Owing to these peculiarities it was
for long assumed that the species of _Prosopis_ must be parasites. This is,
however, known not to be the case so far as many of the species are
concerned. They form cells lined with a silken membrane in the stems of
brambles and other plants that are suitable, or in burrows in the earth, or
in the mortar of walls; individuals of the same species varying much as to
the nidus they select. The food they store in these cells is much more
liquid than usual, and has been supposed to be entirely honey, since they
have no apparatus for carrying pollen. Mr. R. C. L. Perkins has, however,
observed that they swallow both pollen and nectar, brushing the first-named
substance to the mouth by aid of the front legs. He {22}has ascertained
that a few of the very numerous Hawaiian species of the genus are really
parasitic on their congeners: these parasites are destitute of a peculiar
arrangement of hairs on the front legs of the female, the possession of
which, by some of the non-parasitic forms, enables the bee to sweep the
pollen towards its mouth. These observations show that the structural
peculiarities of _Prosopis_ are correlative with the habits of forming a
peculiar lining to the cell, and of gathering pollen by the mouth and
conveying it by the alimentary canal instead of by external parts of the
body. _Prosopis_ is a very widely distributed genus, and very numerous in
species. We have ten in Britain; several of them occur in the grounds of
our Museum at Cambridge.
The species of the genus _Colletes_ are hairy bees of moderate size, with a
good development of hair on the middle and posterior femora for carrying
pollen. They have a short, bilobed ligula like that of wasps, and therein
differ from the Andrenae, which they much resemble. With _Prosopis_ they
form the group Obtusilingues of some taxonomists. They have a manner of
nesting peculiar to themselves; they dig cylindrical burrows in the earth,
line them with a sort of slime, that dries to a substance like
gold-beater's skin, and then by partitions arrange the burrow as six to ten
separate cells, each of which is filled with food that is more liquid than
usual in bees. Except in regard to the ligula and the nature of the
cell-lining, _Colletes_ has but little resemblance to _Prosopis_; but the
term Obtusilingues may be applied to _Colletes_ if _Prosopis_ be separated
as Archiapidae. We have six species of _Colletes_ in Britain.
_Sphecodes_ is a genus that has been the subject of prolonged difference of
opinion. The species are rather small shining bees, with a red, or red and
black, abdomen, almost without pollen-collecting apparatus, and with a
short but pointed ligula. These characters led to the belief that the
Insects are parasitic, or, as they are sometimes called, cuckoo-bees. But
evidence could not be obtained of the fact, and as they were seen to make
burrows it was decided that we have in _Sphecodes_ examples of industrial
bees extremely ill endowed for their work. Recent observations tend,
however, to prove that _Sphecodes_ are to a large extent parasitic at the
expense of bees of the genera _Halictus_ and _Andrena_. Breitenbach has
taken _S. rubicundus_ out of the brood-cells of _Halictus quadricinctus_;
and on one of the few {23}occasions on which this bee has been found in
Britain it was in circumstances that left little doubt as to its being a
parasite of _Andrena nigroaenea_. Marchal[21] has seen _S. subquadratus_
fight with _Halictus malachurus_, and kill it previous to taking possession
of its burrows; and similar observations have been made by Ferton. As the
older observations of Smith, Sichel, and Friese leave little doubt that
_Sphecodes_ are sometimes industrial bees, it is highly probable that we
have in this genus the interesting condition of bees that are sometimes
parasitic, at other times not; but so much obscurity still prevails as to
the habits of _Sphecodes_ that we should do well to delay accepting the
theories that have been already based on this strange state of matters.[22]
Friese states that in _Sphecodes_ the first traces of collecting apparatus
exist; and, accepting the condition of affairs as being that mentioned
above, it is by no means clear whether we have in _Sphecodes_ bees that are
abandoning the parasitic habit or commencing it; or, indeed, whether the
condition of uncertainty may not be a permanent one. It is difficult to
decide as to what forms are species in _Sphecodes_ owing to the great
variation. The Hymenopterist Forster considered that 600 specimens
submitted to him by Sichel represented no less than 140 species, though
Sichel was convinced that nearly the whole of them were one species, _S.
gibbus_. It has recently been found that the male sexual organs afford a
satisfactory criterion. The position of _Sphecodes_ in classification is
doubtful.
[Illustration: Fig. 11.—_Sphecodes gibbus_ ♀. Britain.]
The great majority of the species of short-tongued bees found in Britain
belong to the genera _Andrena_ and _Halictus_, and with some others
constitute the Andrenides of many writers. _Halictus_ includes our smallest
British bees. Their economy escaped the earlier observers, but has recently
been to some extent unravelled by Smith, Fabre, Nicolas, Verhoeff, and
others, and proves to be {24}of great interest and variety. Fabre observed
_H. lineolatus_ and _H. sexcinctus_[23] under circumstances that enabled
him to give them continuous attention, whenever requisite, throughout a
whole year. These bees are to a certain extent social; they are gregarious;
each bee works for its own progeny, but there is collaboration between
members of a colony, inasmuch as a piece of general work is undertaken from
which more families than one derive benefit. This common work is a gallery,
that, ramifying in the earth, gives access to various groups of cells, each
group the production of a single _Halictus_; in this way one entrance and
one corridor serve for several distinct dwellings. The work of excavation
is carried on at night. The cells are oval, and are covered on the interior
with a delicate waterproof varnish; Fabre considers this to be a product of
the salivary glands, like the membrane we noticed when speaking of
_Colletes_. In the south of France both sexes of these species are produced
from the nests in September, and then the males are much more numerous than
the females; when the cold weather sets in the males die, but the females
continue to live on in the cells underground. In the following spring the
females come out and recommence working at the burrows, and also provision
the cells for the young; the new generation, consisting entirely of
females, appears in July, and from these there proceeds a parthenogenetic
generation, which assumes the perfect form in September, and consists, as
we have above remarked, in greater part of males. Pérez,[24] however,
considers that Fabre's observations as to the parthenogenetic generation
were incomplete, and that males might have been found a little earlier, and
he consequently rejects altogether the occurrence of parthenogenesis in
_Halictus_. Nicolas confirms Fabre's observations, so far as the
interesting point of the work done for common benefit is concerned; and
adds that the common corridor being too narrow to permit of two bees
passing, there is a dilatation or vestibule near the entrance that
facilitates passage, and also that a sentinel is stationed at this point.
Smith's observations on _Halictus morio_ in England lead one to infer that
there is but one generation, the appearance of which extends over a very
long period. He says, "Early in April the females appeared, and continued
in numbers up to the end of {25}June"; then there was an interval, and in
the middle of August males began to appear, followed in ten or twelve days
by females. Hence it is probable that in different countries the times of
appearance and the number of generations of the same species may vary.
Verhoeff has described the burrows of _Halictus quadricinctus_ with some
detail. The cells, instead of being distributed as usual throughout the
length of the burrow one by one, are accumulated into a mass placed in a
vault communicating with the shaft. This shaft is continued downwards to a
depth of 10 cm., and forms a retreat for the bees when engaged in
construction. Several advantages are secured by this method, especially
better ventilation, and protection from any water that may enter the shaft.
The larvae that are present in the brood-chambers at any one moment differ
much in their ages, a fact that throws some doubt on the supposed
parthenogenetic generation. No cocoons are formed by these _Halictus_, the
polished interior of the cell being a sufficiently refined resting place
for metamorphosis. Verhoeff states that many of the larvae are destroyed by
mouldiness; this indeed, he considers to be the most deadly of the enemies
of Aculeate Hymenoptera. The nest of _Halictus maculatus_ has also been
briefly described by Verhoeff, and is a very poor construction in
comparison with that of _H. quadricinctus_.
[Illustration: Fig. 12—Nesting of _Halictus quadricinctus_. _u_, Original
burrow, with entrance _e_ thereto; _n_, retreat or continuation of the
burrow; _w_, the vaults; _s_, the accumulation of cells. (After Verhoeff,
_Verh. Ver. Rheinl._ xlviii. 1891; scale not mentioned.)]
The genus _Andrena_ includes a great number of species, Britain possessing
about fifty. They may be described in a general manner as Insects much
resembling the honey-bee—for which, indeed, they are frequently
mistaken—but usually a little smaller in size. Many of the bees we see in
spring, in March or April, are of this genus. They live in burrows in the
ground, preferring sandy places, but frequently selecting a gravel path as
the locality for their operations; they nearly always live {26}in colonies.
Great difficulties attend their study on account of several points in their
economy, such as, that the sexes are different, and frequently not found
together; also that there may be two generations of a species in one year,
these being more or less different from one another. Another considerable
difficulty arises from the fact that these bees are subject to the attacks
of the parasite _Stylops_, by which their form is more or less altered.
These Insects feed in the body of the bee in such a way as to affect its
nutrition without destroying its life; hence they offer a means of making
experiments that may throw valuable light on obscure physiological
questions. Among the effects they produce in the condition of the imago bee
we may mention the enfeeblement of the sexual distinction, so that a
stylopised male bee becomes less different than it usually is from the
female, and a stylopised female may be ill developed and less different
than usual from the male. The colours and hair are sometimes altered, and
distortion of portions of the abdominal region of the bee are very common.
Further particulars as to these parasites will be found at the end of our
account of Coleoptera (p. 298). We may here remark that these _Stylops_ are
not the only parasitic Insects that live in the bodies of Andrenidae
without killing their hosts, or even interrupting their metamorphoses. Mr.
R. C. L. Perkins recently captured a specimen of _Halictus rubicundus_,
from which he, judging from the appearance of the example, anticipated that
a _Stylops_ would emerge; but instead of this a Dipterous Insect of the
family Chloropidae appeared. Dufour in 1837 called attention to a
remarkable relation existing between _Andrena aterrima_ and a parasitic
Dipterous larva. The larva takes up a position in the interior of the bee's
body so as to be partly included in one of the great tracheal vesicles at
the base of the abdomen; and the bee then maintains the parasite in its
position, and at the same time supplies it with air by causing two tracheae
to grow into its body. Dufour states that he demonstrated the continuity of
the tracheae of the two organisms, but it is by no means clear that the
continuity was initially due to the bee's organisation.
[Illustration: Fig. 13—Parasitic Dipterous larva in connection with
tracheal system of _Andrena aterrima_. (After Dufour.)]
{27}[Illustration: Fig. 14.—_D. hirtipes_ ♀. Britain.]
_Dasypoda hirtipes_ appears to be the most highly endowed of the European
Andrenides. The Insects of the genus _Dasypoda_ are very like _Andrena_,
but have only two in place of three submarginal cells (just beneath the
stigma) on the front wing. The female of _D. hirtipes_ has a very dense and
elongate pubescence on the posterior legs, and carries loads of pollen,
each about half its own weight, to its nest. The habits of this insect have
been described by Hermann Müller.[25] It forms burrows in the ground after
the fashion of _Andrena_; this task is accomplished by excavating with the
mandibles; when it has detached a certain quantity of the earth it brings
this to the surface by moving backwards, and then distributes the loose
soil over a considerable area. It accomplishes this in a most beautiful
manner by means of the combined action of all the legs, each pair of these
limbs performing its share of the function in a different manner; the front
legs acting with great rapidity—making four movements in a second—push the
sand backwards under the body, the bee moving itself at the same time in
this direction by means of the middle pair of legs; simultaneously, but
with a much slower movement, the hind legs are stretched and moved
outwards, in oar-like fashion, from the body, and thus sweep away the earth
and distribute it towards each side. This being done the bee returns
quickly into the hole, excavates some more earth, brings it up and
distributes it. Each operation of excavation takes a minute or two, the
distribution on the surface only about fifteen seconds. The burrow extends
to the length of one or two feet, so that a considerable amount of earth
has to be brought up; and when the Insect has covered one part of the
circumference of the mouth of the hole with loose earth, it makes another
patch, or walk, by the side of the first. The main burrow being completed,
the Insect then commences the formation of brood-chambers in connection
with it. Three to six such chambers are formed in connection with a burrow;
the lower one is first made and is provisioned by the bee: for this
{28}purpose five or six loads of pollen are brought to the cell, each load
being, as we have already remarked, about half the weight of the Insect.
This material is then formed into a ball and made damp with honey; then
another load of pollen is brought, is mixed with honey and added as an
outer layer to the ball, which is now remodelled and provided on one side
with three short feet, after which an egg is placed on the top of the mass;
the bee then sets to work to make a second chamber, and uses the material
resulting from the excavation of this to close completely the first
chamber. The other chambers are subsequently formed in a similar manner,
and then the burrow itself is filled up. While engaged in ascertaining
these facts, Müller also made some observations on the way the bee acts
when disturbed in its operations, and his observations on this point show a
very similar instinct to that displayed by _Chalicodoma_, referred to on a
subsequent page. If interrupted while storing a chamber the Insect will not
attempt to make a fresh one, but will carry its stock of provisions to the
nest of some other individual. The result of this proceeding is a struggle
between the two bees, from which it is satisfactory to learn that the
rightful proprietor always comes out victorious. The egg placed on the
pollen-ball in the chamber hatches in a few days, giving birth to a
delicate white larva of curved form. This creature embraces the pollen-ball
so far as its small size will enable it to do so, and eats the food layer
by layer so as to preserve its circular form. The larva when hatched has no
anal orifice and voids no excrement, so that its food is not polluted; a
proper moulting apparently does not take place, for though a new delicate
skin may be found beneath the old one this latter is not definitely cast
off. When the food, which was at first 100 to 140 times larger than the egg
or young larva, is all consumed the creature then for the first time voids
its refuse. During its growth the larva becomes red and increases in weight
from .0025 grains to .26 or .35 grains, but during the subsequent period of
excretion it diminishes to .09 or .15 grains, and in the course of doing so
becomes a grub without power of movement, and of a white instead of a red
colour. After this the larva reposes motionless for many months—in fact,
until the next summer, when it throws off the larval skin and appears as a
pupa. The larval skin thus cast off contrasts greatly with the previous
delicate {29}condition of the integument, for this last exuvium is thick
and rigid. Although it voids no excrement till much later the union of the
stomach and hind-intestine is accomplished when the larva is half-grown. A
larva, from which Müller took away a portion of its unconsumed food-store,
began directly afterwards to emit excrement. The pupa has greater power of
movement than the resting larva; when it has completed its metamorphosis
and become a perfect Insect, it, if it be a female, commences almost
immediately after its emergence to form burrows by the complex and perfect
series of actions we have described.
PARASITIC BEES (Denudatae).—This group of parasitic bees includes fourteen
European genera, of which six are British. They form a group taxonomically
most unsatisfactory, the members having little in common except the
negative characters of the absence of pollen-carrying apparatus. Although
there is a great dearth of information as to the life-histories of
parasitic bees, yet some highly interesting facts and generalisations about
their relations with their hosts have already been obtained. Verhoeff has
recently given the following account of the relations between the parasitic
bee _Stelis minuta_ and its host _Osmia leucomelana_:—The _Osmia_ forms
cells in blackberry stems, provisions them in the usual manner, and
deposits an egg in each. But the _Stelis_ lays an egg in the store of
provisions before the _Osmia_ does, and thus its egg is placed lower down
in the mass of food than that of the legitimate owner, which is in fact at
the top. The _Stelis_ larva emerges from the egg somewhat earlier than the
_Osmia_ larva does. For a considerable time the two larvae so disclosed
consume together the stock of provisions, the _Osmia_ at the upper, the
_Stelis_ at the lower, end thereof. By the consumption of the provisions
the two larvae are brought into proximity, and by this time the _Stelis_
larva, being about twice the size of the _Osmia_ larva, kills and eats it.
Verhoeff witnessed the struggle between the two larvae, and states further
that the operation of eating the _Osmia_ larva after it has been killed
lasts one or two days. He adds that parasitic larvae are less numerous than
the host larvae, it being well known that parasitic bees produce fewer
offspring than host bees. Verhoeff further states that he has observed
similar relations to obtain between the larvae of other parasitic bees and
their hosts, but warns us against concluding that the facts are analogous
in all cases.
{30}[Illustration: Fig. 15.—_Nomada sex-fasciata_ ♀. Britain.]
Fabre has made us acquainted with some points in the history of another
species of the same genus, viz. _Stelis nasuta_, that show a decided
departure from the habits of _S. minuta_. The first-named Insect
accomplishes the very difficult task of breaking open the cells of the
mason-bee, _Chalicodoma muraria_, after they have been sealed up, and then,
being an Insect of much smaller size than the _Chalicodoma_, places several
eggs in one cell of that bee. Friese informs us that parasitic bees and
their hosts, in a great number of cases, not only have in the perfect state
the tongue similarly formed, but also frequent the same species of flower;
thus _Colletes daviesanus_ and its parasite _Epeolus variegatus_ both
specially affect the flowers of _Tanacetum vulgare_. Some of the parasitic
bees have a great resemblance to their hosts; _Stelis signata_, for
instance, is said to be so like _Anthidium strigatum_ that for many years
it was considered to be a species of the genus _Anthidium_. In other cases
not the least resemblance exists between the parasites and hosts. Thus the
species of _Nomada_ that live at the expense of species of the genus
_Andrena_ have no resemblance thereto. Friese further tells us that the
_Andrena_ and _Nomada_ are on the most friendly terms. _Andrena_, as is
well known, forms populous colonies in banks, paths, etc., and in these
colonies the destroying _Nomada_ flies about unmolested; indeed, according
to Friese, it is treated as a welcome guest. He says he has often seen, and
in several localities, _Nomada lathburiana_ and _Andrena ovina_ flying
peacefully together. The _Nomada_ would enter a burrow, and if it found the
_Andrena_ therein, would come out and try another burrow; if when a
marauding _Nomada_ was in a burrow, and the rightful owner, returning laden
with pollen, found on entering its home that an uninvited guest was
therein, the _Andrena_ would go out in order to permit the exit of the
_Nomada_, and then would again enter and add the pollen to the store.
Strange as this may seem at first sight, it is really not so, for, as we
have before had occasion to observe, there is not the slightest reason for
believing that host Insects have any idea whatever that the parasites or
inquilines are injurious to their {31}race. Why then should they attack the
creatures? Provided the parasites do not interfere in any unmannerly way
with the hosts and their work, there is no reason why the latter should
resent their presence. The wild bee that seals up its cell when it has laid
an egg therein, and then leaves it for ever, has no conception of the form
of its progeny; never in the history of the race of the _Andrena_ has a
larva seen a perfect insect and survived thereafter, never has a perfect
Insect seen a larva. There is no reason whatever for believing that these
Insects have the least conception of their own metamorphosis, and how then
should they have any idea of the metamorphosis of the parasite? If the
_Andrena_ found in the pollen the egg of a parasitic _Nomada_, it could of
course easily remove the egg; but the _Andrena_ has no conception that the
presence of the egg ensures the death of its own offspring and though the
egg be that of an enemy to its race, why should it resent the fact? Is it
not clear that the race has always maintained itself notwithstanding the
enemy? Nature has brought about that both host and parasite should
successfully co-exist; and each individual of each species lives, not for
itself, but for the continuance of the species; that continuance is
provided for by the relative fecundities of host and guest. Why then should
the _Andrena_ feel alarm? If the species of _Nomada_ attack the species of
_Andrena_ too much it brings about the destruction of its own species more
certainly than that of the _Andrena_.
[Illustration: Fig. 16.—_Melecta luctuosa_ ♀. Britain.]
Such extremely friendly relations do not, however, exist between all the
parasitic bees and their hosts. Friese says that, so far as he has been
able to observe, the relations between the two are not in general friendly.
He states that marauders of the genera _Melecta_ and _Coelioxys_ seek to
get out of the way when they see the pollen-laden host coming home. But he
does not appear to have noted any other evidence of mistrust between the
two, and it is somewhat doubtful whether this act can properly be
interpreted as indicating fear, for bees, as well as other animals, when
engaged in work find it annoying to be interfered {32}with; it is the
interest of the parasite to avoid annoyance and to be well-mannered in its
approaches. Shuckard, however, says that battles ensue between the parasite
_Melecta_ and its host _Anthophora_, when the two bees meet in the burrows
of the _Anthophora_.[26]
We shall have occasion to remark on some of the habits of _Dioxys cincta_
when considering the history of the mason-bee (_Chalicodoma_), but one very
curious point in its economy must here be noticed. The _Dioxys_, which is a
much smaller bee than the _Chalicodoma_, lays an egg in a cell of the
latter, and the resulting larva frequently has more food in the cell than
it can consume; there is, however, another bee, _Osmia cyanoxantha_, that
frequently takes advantage of an unoccupied cell in the nest of the
_Chalicodoma_, and establishes its own offspring therein. The _Dioxys_, it
seems, cannot, or at any rate does not, distinguish whether a cell is
occupied by _Chalicodoma_ or by _Osmia_, and sometimes lays its egg in the
nest of the _Osmia_, though this bee is small, and therefore provides very
little food for its young. It might be supposed that under these conditions
the _Dioxys_ larva would be starved to death; but this is not so; it has
the power of accommodating its appetite, or its capacity for metamorphosis,
to the quantity of food it finds at its disposal, and the egg laid in the
_Osmia_ cell actually produces a tiny specimen of _Dioxys_, only about half
the natural size. Both sexes of these dwarf _Dioxys_ are produced, offering
another example of the fact that the quantity of food ingested during the
lifetime of the larva does not influence the sex of the resulting imago.
The highly endowed bees that remain to be considered are by some writers
united in a group called Apidae, in distinction from Andrenidae. For the
purposes of this work we shall adopt three divisions, Scopulipedes,
Dasygastres, Sociales.
The group Scopulipedes includes such long-tongued, solitary bees as are not
parasitic, and do not belong to the Dasygastres. It is not, however, a
natural group, for the carpenter-bees (_Xylocopa_) are very different from
_Anthophora_. It has recently been merged by Friese with Andrenides into a
single group called Podilegidae. Four British genera, _Ceratina_,
_Anthophora_, _Eucera_ and _Saropoda_ (including, however, only seven
{33}species), are referred to the Scopulipedes; in some forms a
considerable resemblance to the Bombi is exhibited, indeed the female of
one of our species of _Anthophora_ is so very like the worker of _Bombus
hortorum_ var. _harrisellus_, that it would puzzle any one to distinguish
them by a superficial inspection, the colour of the hair on the hind legs
being the only obvious difference. _Anthophora_ is one of the most
extensive and widely distributed of the genera of bees. Some of the species
make burrows in cliffs and form large colonies which are continued for many
years in the same locality. Friese has published many details of the
industry and metamorphoses of some of the species of this genus; the most
remarkable point he has discovered being that _A. personata_ at Strasburg
takes two years to accomplish the life-cycle of one generation. Some of the
European species of the genus have been found to be very subject to the
attacks of parasites. An anomalous beetle, _Sitaris_, has been found in the
nests of _A. pilipes_; and this same _Anthophora_ is also parasitised by
another beetle, _Meloe_, as well as by a bee of the genus _Melecta_.
The genus _Xylocopa_[27] contains many of the largest and most powerful of
the bees, and is very widely distributed over the earth. In Europe only
four or five species have been found, and none of them extend far
northwards, _X. violacea_ being the only one that comes so far as Paris.
They are usually black or blue-black in colour, of broad, robust build,
with shining integuments more or less covered with hair. _X. violacea_ is
known as the carpenter-bee from its habit of working in dry wood; it does
not touch living timber, but will form its nest in all sorts of dried wood.
It makes a cylindrical hole, and this gives access to three or four
parallel galleries in which the broad cells are placed; the cells are
always isolated by a partition; the bee forms this by cementing together
with the products of its salivary glands the fragments of wood it cuts out.
Its habits have been described at length by Réaumur, who alludes to it
under the name of "abeille perce-bois." This bee hibernates in the imago
condition, both sexes reappearing in the spring. Possibly there is more
than one generation in the year, as Réaumur states that specimens that were
tiny larvae on the 12th of June had by the 2nd of July consumed all their
stock of provisions; they then fasted for a few days, and on the 7th or 8th
of July became pupae, and in the first {34}days of August were ready to
emerge as perfect Insects. Thus the whole cycle of metamorphoses is passed
through in about eight weeks. This species, though very clever in drilling
holes, does not hesitate to appropriate old burrows should they be at hand.
Fabre observed that it was also quite willing to save itself labour by
forming its cells in hollow reeds of sufficient calibre. We have figured
the larva and pupa of this species in the previous volume (p. 170).
[Illustration: Fig. 17.—_Xylocopa_ (_Koptorthosoma_), sp. near
_flavonigrescens_, ♂. Sarawak.]
_Xylocopa chloroptera_ in E. India selects a hollow bamboo for its nidus;
it cements together the pieces obtained in clearing out the bamboo, and
uses them as horizontal partitions to separate the tube into cells. The
species is much infested with a small Chalcid of the genus _Encyrtus_: 300
specimens of the parasite have been reared from a single larva of the bee;
two-thirds of the larvae of this bee that Horne endeavoured to rear were
destroyed by the little Chalcid.
The most beautiful and remarkable of all the bees are the species of
_Euglossa_. This genus is peculiar to Tropical America, and derives its
name from the great length of the proboscis, which in some species
surpasses that of the body. The colours in _Euglossa_ proper are violet,
purple, golden, and metallic green, and two of these are frequently
combined in the most harmonious manner; the hind tibia is greatly developed
and forms a plate, the outer surface of which is highly polished, while the
margins are furnished with rigid hairs. Very little is known as to the
habits of these bees; they were formerly supposed to be {35}social; but
this is doubtful, Bates having recorded that _E. surinamensis_ forms a
"solitary nest." Lucas concluded that _E. cordata_ is social, on the
authority of a nest containing "a dozen individuals." No workers are known.
The species of _Eulema_ have a shorter tongue than _Euglossa_, and in form
and colour a good deal resemble our species of _Bombus_ and _Apathus_.
The group Dasygastres includes seven European genera, four being British
(_Chelostoma_ being included in _Heriades_). The ventral surface of the
hind body is densely set in the females with regularly arranged hairs, by
means of which the pollen is carried. In many of the Dasygastres
(_Megachile_, _e.g._) the labrum is very large, and in repose is inflected
on to the lower side of the head, and closely applied to the doubled-in
tongue, which it serves to protect; the mandibles then lock together
outside the labrum, which is thus completely concealed. This group includes
some of the most interesting of the solitary bees.
[Illustration: Fig. 18.—_Euglossa cordata_, ♂. Amazons. A, The Insect with
extended proboscis; B, outer face of hind tibia and tarsus.]
The genus _Chalicodoma_ is not found in our own country, but in the South
of France there exist three or four species. Their habits have given rise
to much discussion, having been described by various naturalists, among
whom are included Réaumur and Fabre. These Insects are called mason-bees,
and construct nests of very solid masonry. _C. muraria_ is in appearance
somewhat intermediate between a honey-bee and a _Bombus_; it is densely
hairy, and the sexes are very different in colour. It is solitary in its
habits, and usually chooses a large stone as a solid basis for its
habitation. On this a cell is formed, the material used being a kind of
cement made by the Insect from the mixture of a {36}suitable sort of earth
with the material secreted by its own salivary glands; the amount of cement
used is reduced by the artifice of building small stones into the walls of
the cell; the stones are selected with great care. When a cell about an
inch in depth has been formed in this manner, the bee commences to fill it
with food, consisting of honey and pollen; a little honey is brought and is
discharged into the cell, then some pollen is added. This bee, like other
Dasygastres, carries the pollen by means of hairs on the under surface of
the body; to place this pollen in the cell the Insect therefore enters
backwards, and then with the pair of hind legs brushes and scrapes the
under surface of the body so as to make the pollen fall off into the cell;
it then starts for a fresh cargo; after a few loads have been placed in the
receptacle, the Insect mixes the honey and pollen into a paste with the
mandibles, and again continues its foraging until it has about half filled
the cell; then an egg is laid, and the apartment is at once closed with
cement. This work is all accomplished, if the weather be favourable, in
about two days, after which the Insect commences the formation of a second
cell, joined to the first, and so on till eight or nine of these
receptacles have been constructed; then comes the final operation of adding
an additional protection in the shape of a thick layer of mortar placed
over the whole; the construction, when thus completed, forms a sort of dome
of cement about the size of half an orange. In this receptacle the larvae
pass many months, exposed to the extreme heat of summer as well as to the
cold of winter. The larvae, however, are exposed to numerous other perils;
and we have already related (vol. v. p. 540) how _Leucospis gigas_ succeeds
in perforating the masonry and depositing therein an egg, so that a
_Leucospis_ is reared in the cell instead of a _Chalicodoma_.
[Illustration: Fig. 19—_Chalicodoma muraria_. Greece. A, Male; B, female.]
{37}This Insect has been the object of some of J. H. Fabre's most
instructive studies on instinct.[28] Although it is impossible for us here
to consider in a thorough manner the various points he has discussed, yet
some of them are of such interest and importance as to demand something
more than a passing allusion.
We have mentioned that the nest of _Chalicodoma_ is roofed with a layer of
solid cement in addition to the first covering with which the bee seals up
each cell. When the metamorphoses of the imprisoned larva have been passed
through, and the moment for its emergence as a perfect Insect has arrived,
the prisoner has to make its way through the solid wall by which it is
encompassed. Usually it finds no difficulty in accomplishing the task of
breaking through the roof, so that the powers of its mandibles must be very
great. Réaumur has, however, recorded that a nest of this mason-bee was
placed under a glass funnel, the orifice of which was covered with gauze,
and that the Insects when they emerged from the nest were unable to make
their way through the gauze, and consequently perished under the glass
cover; and he concluded that such insects are only able to accomplish the
tasks that naturally fall to their lot. By some fresh experiments Fabre,
however, has put the facts in a different light. He remarks that when the
Insects have, in the ordinary course of emergence, perforated the walls of
their dark prison, they find themselves in the daylight, and at liberty to
walk away; when they have made their escape from a nest placed under a
glass cover, they, having no knowledge of glass, find themselves in
daylight and imprisoned by the glass, which, to their inexperience, does
not appear to be an obstacle, and they therefore, he thought, might perhaps
exhaust themselves in vain efforts to pass through this invisible obstacle.
He therefore took some cocoons containing pupae from a nest, placed each
one of them in a tube of reed, and stopped the ends of the reeds with
various substances, in one case earth, in another pith, in a third brown
paper; the reeds were then so arranged that the Insects in them were in a
natural position; in due course all the Insects emerged, none of them
apparently having found the novel nature of the obstacle a serious
impediment. Some complete nests were then taken with their inmates, and to
the exterior of one of them a sheet of opaque paper was closely fastened,
while to another the same {38}sort of paper was applied in the form of a
dome, leaving thus a considerable space between the true cover of the nest
and the covering of paper. From the first nest the Insects made their
escape in the usual manner, thus again proving that paper can be easily
pierced by them. From the second nest they also liberated themselves, but
failed to make their way out through the dome of paper, and perished
beneath it; thus showing that paper added to the natural wall caused them
no difficulty, but that paper separated therefrom by a space was an
insuperable obstacle. Professor Pérez has pointed out that this is no doubt
due to the large space offered to the bee, which consequently moves about,
and does not concentrate its efforts on a single spot, as it of course is
compelled to do when confined in its natural cell.
The power of the mason-bee to find its nest again when removed to a
distance from it is another point that was tested by Du Hamel and recounted
by Réaumur. As regards this Fabre has also made some very valuable
observations. He marked some specimens of the bee, and under cover removed
them to a distance of four kilometres, and then liberated them; the result
proved that the bees easily found their way back again, and indeed were so
little discomposed by the removal that they reached their nests laden with
pollen as if they had merely been out on an ordinary journey. On one of
these occasions he observed that a _Chalicodoma_, on returning, found that
another bee had during her absence taken possession of her partially
completed cell, and was unwilling to relinquish it; whereupon a battle
between the two took place. The account of this is specially interesting,
because it would appear that the two combatants did not seek to injure one
another, but were merely engaged in testing, as it were, which was the more
serious in its claims to the proprietorship of the cell in dispute. The
matter ended by the original constructor regaining and retaining
possession. Fabre says that in the case of _Chalicodoma_ it is quite a
common thing for an uncompleted cell to be thus appropriated by a stranger
during the absence of the rightful owner, and that after a scene of the
kind described above, the latter of the two claimants always regains
possession, thus leading one to suppose that some sense of rightful
ownership exists in these bees; the usurper expressing, as it were, by its
actions the idea—Before I {39}resign my claims I must require you to go
through the exertions that will prove you to be really the lawful owner.
Another experiment was made with forty specimens of _Chalicodoma
pyrenaica_, which were removed to a distance of four kilometres and then
liberated. About twenty of the individuals had been somewhat injured by the
processes of capturing, marking, and transferring, and proved unable to
make a proper start. The others went off well when released, and in forty
minutes the arrivals at the nest had already commenced. The next morning he
was able to ascertain that fifteen at least had found their way back, and
that it was probable that most of the uninjured bees had reached home; and
this although, as Fabre believed, they had never before seen the spot where
he liberated them.
These observations on the power of _Chalicodoma_ to regain its nest
attracted the attention of Charles Darwin, who wrote to M. Fabre, and
suggested that further observations should be made with the view of
ascertaining by means of what sense these bees were able to accomplish
their return. For it must be borne in mind that this bee is very different
from the domestic bee, inasmuch as it enjoys but a brief life in the winged
state, and it is therefore to be presumed that an individual has no
knowledge of such comparatively distant localities as those to which Fabre
transported it. Further observations made by the Frenchman have
unfortunately failed to throw any light on this point. Darwin thought it
might possibly be some sensitiveness to magnetic conditions that enabled
the bees to return home, and suggested that they should be tested as to
this. Fabre accordingly made some minute magnets, and fixed one to each bee
previous to letting them loose for a return journey. This had the effect of
completely deranging the bees; and it was therefore at first thought that
the requisite clue was obtained. It occurred to the experimenter, however,
to try the plan of affixing small pieces of straw to the bees instead of
magnets, and on this being done it was found that the little creatures were
just as much deranged by the straws as they were by the magnets: thus it
became evident that no good grounds exist for considering that the bees are
guided by magnetic influences.
One of the species[29] of _Chalicodoma_ observed by Fabre fixes {40}its
nests to the small boulders brought down and left by the Rhone on the waste
places of its banks. This habit afforded Fabre an opportunity of removing
the nests during the process of construction, and of observing the effect
this produced on the architects. While a bee that had a nest partially
constructed was absent, he removed the stone and the nest attached to it
from one situation to another near at hand and visible from the original
site. In a few minutes the bee returned and went straight to the spot where
the nest had been; finding its home absent it hovered for a little while
around the place, and then alighted on the vacated position, and walked
about thereon in search of the nest; being after some time convinced that
this was no longer there, it took wing, but speedily returned again to the
place and went through the same operations. This series of manoeuvres was
several times repeated, the return always being made to the exact spot
where the nest had been originally located; and although the bee in the
course of its journeys would pass over the nest at a distance of perhaps
only a few inches, it did not recognise the object it was in search of. If
the nest were placed very near to the spot it had been removed from—say at
a distance of about a yard—it might happen that the bee would actually come
to the stone to which the nest was fixed, would visit the nest, would even
enter into the cell it had left partially completed, would examine
circumspectly the boulder, but would always leave it, and again return to
the spot where the nest was originally situated, and, on finding that the
nest was not there, would take its departure altogether from the locality.
The home must be, for the bee, in the proper situation, or it is not
recognised as the desired object. Thus we are confronted with the strange
fact that the very bee that is able to return to its nest from a distance
of four kilometres can no longer recognise it when removed only a yard from
the original position. This extraordinary condition of the memory of the
Insect is almost inconceivable by us. That the bee should accurately
recognise the spot, but that it should not recognise the cell it had itself
just formed and half-filled with honey-paste, seems to us almost
incredible; nevertheless, the fact is quite consistent with what we shall
subsequently relate in the case of the solitary wasp _Bembex_. A cross
experiment was made by taking away the stone with the attached nest of the
bee while the latter {41}was absent, and putting in its place the nest of
another individual in about the same stage of construction; this nest was
at once adopted by the bee, which indeed was apparently in no way deranged
by the fact that the edifice was the work of another. A further experiment
was made by transposing the positions of two nests that were very near
together, so that each bee when returning might be supposed to have a free
choice as to which nest it would go to. Unhesitatingly each bee selected
the nest that, though not its own, was in the position where its own had
been. This series of experiments seems to prove that the _Chalcidoma_ has
very little sense as to what is its own property, but, on the other hand,
has a most keen appreciation of locality. As, however, it might be supposed
that the bees were deceived by the similarity between the substituted
nests, Fabre transposed two nests that were extremely different, one
consisting of many cells, the other of a single incomplete cell; it was, of
course, a necessary condition of this experiment that each of the two
nests, however different in other respects, should possess one cell each in
similar stages of construction; and when that was the case each bee
cheerfully adopted the nest that, though very different to its own, was in
the right place. This transposition of nests can be rapidly repeated, and
thus the same bee may be made to go on working at two different nests.
Suppose, however, that another sort of change be made. Let a nest,
consisting of a cell that is in an early stage of construction, be taken
away, and let there be substituted for it a cell built and partially stored
with food. It might be supposed that the bee would gladly welcome this
change, for the adoption of the substituted cell would save it a great deal
of work. Not so, however; the bee in such a case will take to the
substituted cell, but will go on building at it although it is already of
the full height, and will continue building at it until the cell is made as
much as a third more than the regulation height. In fact the bee, being in
the building stage of its operations, goes on building, although in so
doing it is carrying on a useless, if not an injurious, work. A similar
state ensues when the Insect ceases to build and begins to bring provisions
to the nest; although a substituted cell may contain a sufficient store of
food, the bee goes on adding to this, though it is wasting its labours in
so doing. It should be noted that though the bee must go through the
{42}appropriate stages of its labours whether the result of so doing be
beneficial or injurious, yet it is nevertheless to some extent controlled
by the circumstances, for it does not in such cases complete what should
have been the full measure of its own individual work; it does not, for
instance, raise the cell to twice the natural height, but stops building
when the cell is about one-third larger than usual, as if at that stage the
absurdity of the situation became manifest to it.
Fabre's experiments with the _Chalicodoma_ are so extremely instructive as
regards the nature of instinct in some of the highest Insects, that we must
briefly allude to some other of his observations even at the risk of
wearying the reader who feels but little interest in the subject of Insect
intelligence.
Having discovered that a mason-bee that was engaged in the process of
construction would go on building to an useless or even injurious extent,
Fabre tried another experiment to ascertain whether a bee that was engaged
in the process of provisioning the nest, would do so in conditions that
rendered its work futile. Taking away a nest with completely built cell
that a bee was storing with food, he substituted for it one in which the
cell was only commenced, and therefore incapable of containing food; when
the bee with its store of provisions reached this should-be receptacle it
appeared to be very perplexed, tested the imperfect cell with its antennae,
left the spot and returned again; repeating this several times it finally
went to the cell of some stranger to deposit its treasure. In other cases
the bee broke open a completed cell, and having done so went on bringing
provisions to it, although it was already fully provisioned and an egg laid
therein: finally, the little creature having completed the bringing of this
superfluous tale of provisions, deposited a second egg, and again sealed up
the cell. But in no case does the bee go back from the provisioning stage
to the building stage until the cycle for one cell of building,
provisioning, and egg-laying is completed: but when this is the case, the
building of a fresh cell may be again undertaken. This is a good example of
the kind of consecutive necessity that seems to be one of the chief
features of the instinct of these industrious little animals. Another
equally striking illustration of these peculiarities of instinct is offered
by interfering with the act of putting the provisions into the cell. It
will be recollected that {43}when the bee brings provisions to add to the
stock, it carries both honey and pollen; in order to deliver these it
begins by entering head first into the cell and disgorging the honey, then
emerging it turns round, enters backwards and scrapes off the pollen from
its body. If after the honey has been discharged, the bee be interfered
with and gently removed to a slight distance with a straw, it returns to
complete its task, but instead of going on with the actions at the point at
which the interruption took place, it begins the series over again, going
in—at any rate partially—head first, although it has no honey to discharge,
and having performed this useless ceremony it then emerges, turns round and
adds the pollen. This illustration is in some respects the reverse of what
might have been expected, for the Insect here does not continue the act at
the interrupted point, but begins the series of actions afresh.
It would be reasonable to suppose that an Insect that takes the pains to
provide for the safety of its progeny by constructing a complex edifice of
cement, secures thereby the advantage of protection for its young. But this
is far from being the case. Notwithstanding the cement and the thick dome
of mortar, the _Chalicodoma_ is extremely subject to the attacks of
parasites. The work performed by the creature in constructing its mass of
masonry is truly astounding; Fabre calculated from measurements he made
that for the construction and provisioning of a single cell, the goings and
comings of the bee amounted to 15 kilometres, and it makes for each nest
sometimes as many as fifteen cells. Notwithstanding all this labour, it
would appear that no real safety for the larvae is obtained by the work.
Some sixteen—possibly more—other species of Insects get their living off
this industrious creature. Another bee, _Stelis nasuta_, breaks open the
cells after they have been completely closed and places its own eggs in
them, and then again closes the cells with mortar. The larvae of this
_Stelis_ develop more rapidly than do those of the _Chalicodoma_, so that
the result of this shameless proceeding is that the young one of the
legitimate proprietor—as we human beings think it—is starved to death, or
is possibly eaten up as a dessert by the _Stelis_ larvae, after they have
appropriated all the pudding.
Another bee, _Dioxys cincta_, is even more audacious; it flies about in a
careless manner among the _Chalicodoma_ at their {44}work, and they do not
seem to object to its presence unless it interferes with them in too
unmannerly a fashion, when they brush it aside. The _Dioxys_, when the
proprietor leaves the cell, will enter it and taste the contents; after
having taken a few mouthfuls the impudent creature then deposits an egg in
the cell, and, it is pretty certain, places it at or near the bottom of the
mass of pollen, so that it is not conspicuously evident to the
_Chalicodoma_ when the bee again returns to add to or complete the stock of
provisions. Afterwards the constructor deposits its own egg in the cell and
closes it. The final result is much the same as in the case of the
_Stelis_, that is to say, the _Chalicodoma_ has provided food for an
usurper; but it appears probable that the consummation is reached in a
somewhat different manner, namely, by the _Dioxys_ larva eating the egg of
the _Chalicodoma_, instead of slaughtering the larva. Two of the
Hymenoptera Parasitica are very destructive to the _Chalicodoma_, viz.
_Leucospis gigas_ and _Monodontomerus nitidus_; the habits of which we have
already discussed (vol. v. p. 543) under Chalcididae. Lampert has given a
list of the Insects attacking the mason-bee or found in its nests;
altogether it would appear that about sixteen species have been recognised,
most of which destroy the bee larva, though some possibly destroy the bee's
destroyers, and two or three perhaps merely devour dead examples of the
bee, or take the food from cells, the inhabitants of which have been
destroyed by some untoward event. This author thinks that one half of the
bees' progeny are made away with by these destroyers, while Fabre places
the destruction in the South of France at a still higher ratio, telling us
that in one nest of nine cells, the inhabitants of three were destroyed by
the Dipterous Insect, _Anthrax trifasciata_, of two by _Leucospis_, of two
by _Stelis_, and of one by the smaller Chalcid; there being thus only a
single example of the bee that had not succumbed to one or other of the
enemies. He has sometimes examined a large number of nests without finding
a single one that had not been attacked by one or other of the parasites,
and more often than not several of the marauders had attacked the nest.
It is said by Lampert and others that there is a passage in Pliny relating
to one of the mason-bees, that the Roman author had noticed in the act of
carrying off stones to build into its nest; being unacquainted with the
special habits of the bee, he {45}seems to have supposed that the insect
was carrying the stone as ballast to keep itself from being blown away.
[Illustration: Fig. 20—_Anthidium manicatum_, Carder-bee. A, Male; B,
female.]
The bees of the genus _Anthidium_ are known to possess the habit of making
nests of wool or cotton, that they obtain from plants growing at hand. We
have one species of this genus of bees in Britain; it sometimes may be seen
at work in the grounds of our Museum at Cambridge: it is referred to by
Gilbert White, who says of it, in his _History of Selborne_: "There is a
sort of wild bee frequenting the garden-campion for the sake of its
tomentum, which probably it turns to some purpose in the business of
nidification. It is very pleasant to see with what address it strips off
the pubes, running from the top to the bottom of a branch, and shaving it
bare with the dexterity of a hoop-shaver. When it has got a bundle, almost
as large as itself, it flies away, holding it secure between its chin and
its fore legs." The species of this genus are remarkable as forming a
conspicuous exception to the rule that in bees the female is larger than
the male. The species of _Anthidium_ do not form burrows for themselves,
but either take advantage of suitable cavities formed by other Insects in
wood, or take possession of deserted nests of other bees or even empty
snail-shells. The workers in cotton, of which our British species _A.
manicatum_ is one, line the selected receptacle with a beautiful network of
cotton or wool, and inside this place a finer layer of the material, to
which is added some sort of cement that prevents the honied mass stored by
the bees in this receptacle from passing out of it. _A. diadema_, one of
the species that form nests in hollow stems, has been specially observed by
Fabre; it will take the cotton for {46}its work from any suitable plant
growing near its nest, and does not confine itself to any particular
natural order of plants, or even to those that are indigenous to the South
of France. When it has brought a ball of cotton to the nest, the bee
spreads out and arranges the material with its front legs and mandibles,
and presses it down with its forehead on to the cotton previously
deposited; in this way a tube of cotton is constructed inside the reed;
when withdrawn, the tube proved to be composed of about ten distinct cells
arranged in linear fashion, and connected firmly together by means of the
outer layer of cotton; the transverse divisions between the chambers are
also formed of cotton, and each chamber is stored with a mixture of honey
and pollen. The series of chambers does not extend quite to the end of the
reed, and in the unoccupied space the Insect accumulates small stones,
little pieces of earth, fragments of wood or other similar small objects,
so as to form a sort of barricade in the vestibule, and then closes the
tube by a barrier of coarser cotton taken frequently from some other plant,
the mullein by preference. This barricade would appear to be an ingenious
attempt to keep out parasites, but if so, it is a failure, at any rate as
against _Leucospis_, which insinuates its eggs through the sides, and
frequently destroys to the last one the inhabitants of the fortress. Fabre
states that these _Anthidium_, as well as _Megachile_, will continue to
construct cells when they have no eggs to place in them; in such a case it
would appear from his remarks that the cells are made in due form and the
extremity of the reed closed, but no provisions are stored in the chambers.
The larva of the _Anthidium_ forms a most singular cocoon. We have already
noticed the difficulty that arises, in the case of these Hymenopterous
larvae shut up in small chambers, as to the disposal of the matters
resulting from the incomplete assimilation of the aliment ingested. To
allow the once-used food to mingle with that still remaining unconsumed
would be not only disagreeable but possibly fatal to the life of the larva.
Hence some species retain the whole of the excrement until the food is
entirely consumed, it being, according to Adlerz, stored in a special pouch
at the end of the stomach; other Hymenoptera, amongst which we may mention
the species of _Osmia_, place the excreta in a vacant space. The
_Anthidium_ adopts, however, a most remarkable system: about the middle of
its {47}larval life it commences the expulsion of "frass" in the shape of
small pellets, which it fastens together with silk, as they are voided, and
suspends round the walls of the chamber. This curious arrangement not only
results in keeping the embarrassing material from contact with the food and
with the larva itself, but serves, when the growth of the latter is
accomplished, as the outline or foundations of the cocoon in which the
metamorphosis is completed. This cocoon is of a very elaborate character;
it has, so says Fabre, a beautiful appearance, and is provided with a very
peculiar structure in the form of a small conical protuberance at one
extremity pierced by a canal. This canal is formed with great care by the
larva, which from time to time places its head in the orifice in process of
construction, and stretches the calibre by opening the mandibles. The
object of this peculiarity in the fabrication of the elaborate cocoon is
not clear, but Fabre inclines to the opinion that it is for respiratory
purposes.