THE HOME OF THE BEES.
[_Concluded._]
While the Andrena and Halictus bees, whose habits we now describe, are
closely allied in form to the Hive bee, socially they are the
"mud-sills" of bee society, ranking among the lowest forms of the family
of bees. Their burrowing habits ally them with the ants, from whose
nests their own burrows can scarcely be distinguished. Their economy
does not seem to demand the exercise of so much of a true reasoning
power and pliable instinct as characterizes bees, such as the Honey and
Humble bee, which possess a high architectural skill. Moreover they are
not social; they have no part in rearing and caring for their young, a
fact that lends so much interest to the history of the Hive and Humble
bee. In this respect they are far below the wasps, a family belonging
next below in the system of Nature.
A glance at the drawing (Fig. 28), of a burrow, with its side galleries,
of the Andrena vicina, reveals the economy of one of our most common
forms. Quite early in spring, when the sun and vernal breezes have dried
up the soil, and the fields exchange their rusty hues for the rich green
verdure of May, our Andrena, tired of its idle life among the blossoms
of the willow, the wild cherry, and garden flowers, suddenly becomes
remarkably industrious, and wields its spade-like jaws and busy feet
with a strange and unwonted energy. Choosing some sunny, warm, grassy
bank (these nests were observed in the "great pasture" of Salem), not
always with a southern exposure however, the female sinks her deep well
through the sod from six inches to a foot into the sandy soil beneath.
She goes to work literally tooth and nail. Reasoning from observations
made on several species of wasps, and also from studying the structure
of her jaws and legs, it is evident that she digs in and loosens the
soil with her powerful jaws, and then throws out the dirt with her legs.
She uses her fore legs like hands, to pass the load of dirt to her hind
legs, and then runs backward out of her hole to dump it down behind her.
Mr. Emerton tells me that he never saw a bee in the act of digging but
once, and then she left off after a few strokes. He also says, "they are
harmless and inoffensive. On several occasions I have lain on the grass
near their holes for hours, but not one attempted to sting me; and when
taken between the fingers, they make but feeble resistance."
[Illustration: Fig. 28.
Nest (natural size) of Andrena vicina, showing the main burrow, and the
cells leading from it; the oldest cell containing the pupa (_a_) is
situated nearest the surface, while those containing the larva (_b_) lie
between the pupa and the cell (_e_) containing the pollen mass and egg
resting upon it. The most recent cell (_f_) is the deepest down, and
contains a freshly deposited pollen mass. At _c_ is the beginning of a
cell; _g_, level of the ground.]
To enter somewhat into detail, we gather from the observations of Mr.
Emerton (who has carefully watched the habits of these bees through
several seasons) the following account of the economy of this bee: On
the 4th of May the bees were seen digging their holes, most of which
were already two inches deep, and one, six inches. The mounds of earth
were so small as to be hardly noticed. At this time an Oil beetle was
seen prowling about the holes. The presence of this dire foe of Andrena
at this time, it will be seen in a succeeding chapter on the enemies of
the bees, is quite significant. By the 15th of May, hundreds of Andrena
holes were found in various parts of the pasture, and at one place, in a
previous season, there were about two hundred found placed within a
small area. One cell was dug up, but it contained no pollen. Four days
later, several Andrenas were noticed resting from their toil at the
opening of their burrows. On the 28th of May, in unearthing six holes,
eight cells were found to contain pollen, and in two of them a small
larva. The pellets of pollen are about the size of a small pea. They are
hard and round at first, before the young has hatched, but as the larva
grows, the mass becomes softer and more pasty, so that the larva buries
its head in the mass, and greedily sucks it in. When is the pollen
gathered by the bee and kneaded into the pellet-like mass? On July 4th,
a cell was opened in which was a bee busily engaged preparing the
pollen, which was loosely and irregularly piled up, while there was a
larva in an adjoining cell nearly half an inch long. It would seem,
then, that the bee comes in from the fields laden with her stores of
pollen, which she elaborates into bee bread within her cell.
When the bee returns to her cell she does not directly fly towards the
entrance, since, as was noticed in a particular instance, she flew about
for a long time in all directions without any apparent aim, until she
finally settled near the hole, and walked into her subterranean retreat.
On a rainy day, May 24th, our friend visited the colony, but found no
bees flying about the holes. The little hillocks had been beaten down by
the pitiless raindrops, and all traces of their industry effaced. On
digging down, several bees were found, indicating that on rainy days
they seek the shelter of their holes, and do not take refuge under
leaves of the plants they frequent.
On the 29th of June, six full-grown larvæ were exhumed, and one, about
half grown. On the 20th of July, the colony seemed well organized, as,
on laying open a burrow at the depth of six inches, he began to find
cells. The upper ones, to the number of a dozen, were deserted and
filled with earth and grass roots, and had evidently been built and used
during the previous year. Below these were eight cells placed around the
main vertical gallery, reaching down to the depth of thirteen inches,
and all containing nearly full-grown larvæ of the bees, or else those of
some parasitic bee (Nomada) which had devoured the food prepared for the
young Andrena.
About the first of August the larva transforms to a pupa or chrysalis,
as at this time two pupæ were found in cells a foot beneath the surface.
As shown in the cut, those cells situated lowest down seem to be the
last to have been made, while the eggs laid in the highest are the first
to hatch, and the larvæ disclosed from them, the first to change to
pupæ. Four days later the pupæ of Cuckoo bees (Nomada) were found in the
cells. No Andrenas were seen flying about at this time.
On the 24th of August, to be still very circumstantial in our narrative
though at the risk of being tedious, three burrows were unearthed, and
in them three fully formed bees were found nearly ready to leave their
cells, and in addition several pupæ. In some other cells there were
three of the parasitic Nomada also nearly ready to come out, which
seemed to be identical with some bees noticed playing very innocently
about the holes early in the summer.
On the last day of August, very few of the holes were open. A number of
Oil beetles were strolling suspiciously about in the neighborhood, and
some little black Ichneumon flies were seen running about among the
holes.
During mid-summer the holes were found closed night and day by clods of
earth.
The burrow is sunken perpendicularly, with short passages leading to the
cells, which are slightly inclined downwards and outwards from the main
gallery. The walls of the gallery are rough, but the cells are lined
with a mucous-like secretion, which, on hardening, looks like the
glazing of earthenware. This glazing is quite hard, and breaks up into
angular pieces. It is evidently the work of the bee herself, and is not
secreted and laid on by the larva. The diameter of the interior of the
cell is about one-quarter of an inch, contracting a little at the mouth.
When the cell is taken out, the dirt adheres for a line in thickness, so
that it is of the size and form of an acorn.
The larva of Andrena (Fig. 29) is soft and fleshy, like that of the
Honey bee. Its body is flattened, bulging out prominently at the sides,
and tapering more rapidly than usual towards each end of the body. The
skin is very thin, so that along the back the heart or dorsal vessel may
be distinctly seen, pulsating about sixty times a minute.
Our cut (Fig. 28, _a_) also represents the pupa, or chrysalis, as seen
lying in its cell. The limbs are folded close to the body in the most
compact way possible. On the head of the semi-pupa, _i.e._, a transition
state between the larva and pupa, there are two prominent tubercles
situated behind the simple eyes, or ocelli; these are deciduous organs,
apparently aiding the insect in moving about its cell. They disappear in
the mature pupa.
[Illustration: Fig. 29. Fig. 30. Fig. 31.
Fig. 31. Larva of Halictus parallelus.
Fig. 29. Larva of Andrena vicina.
Fig. 30. Pupa of Halictus parallelus seen from beneath.]
To those accustomed to rearing butterflies, and seeing the chrysalis at
once assuming its perfected shape, after the caterpillar skin is thrown
off, it may seem strange to hear one speak of a "half-pupa," and of
stages intermediate between the larva and pupa. But the external changes
of form, though rapidly passed through, consisting apparently of a mere
sloughing off of the outer skin, are yet preceded by slow and very
gradual alterations of tissues, resulting from the growth of cells. An
inner layer of the larva-skin separates from the outer, and, by changes
in the form of the muscles, is drawn into different positions, such as
is assumed by the pupa, which thus lies concealed beneath the
larva-skin. But a slight alteration is made in the general form of the
larva, consisting mostly of an enlargement of the thoracic segments,
which is often overlooked, even by the special student, though of great
interest to the philosophic naturalist.
From Mr. Emerton's observations we should judge that the pupa state
lasted from three to four weeks, as the larvæ began to transform the
first of August, and appeared during the last week of the same month as
perfect bees.
The Andrena is seen as late as the first week in September, and again
early in April, about the flowers of the willow. It is one of the
largest of its genus and a common species.
Having, in a very fragmentary way, sketched the life history of our
Andrena and had some glimpses of its subterranean life, let us now
compare with it another genus of solitary bee (Halictus), quite closely
allied in all respects, though a little lower in the scale.
The Halictus parallelus excavates cells almost exactly like those of
Andrena; but since the bee is smaller, the holes are smaller, though as
deep. Mr. Emerton found one nest in a path a foot in depth. Another
nest, discovered September 9th, was about six inches deep. The cells are
in form like those of Andrena, and like them, are glazed within. The egg
is rather slenderer and much curved; in form it is long, cylindrical,
obtuse at one end, and much smaller at the other. The larva (Fig. 31) is
longer and slenderer, being quite different from the rather broad and
flattened larva of Andrena. The body is rather thick behind, but in
front tapers slowly towards the head, which is of moderate size. Its
body is somewhat tuberculated, the tubercle aiding the grub in moving
about its cell. Its length is nearly one-half (.40) of an inch. On the
pupa are four quite distinct conical tubercles forming a transverse line
just in front of the ocelli; and there are also two larger, longer
tubercles, on the outer side of each of which, an ocellus is situated.
Figure 30 represents the pupa seen from beneath.
Search was made on July 16th, where the ground was hard as stone for six
inches in depth, below which the soil was soft and fine, and over twenty
cells were dug out. "The upper cells contained nearly mature pupæ, and
the lower ones, larvæ of various sizes, the smallest being hardly
distinguishable by the naked eye. Each of these small larvæ was in a
cell by itself, and situated upon a lump of pollen, which was the size
and shape of a pea, and was found to lessen in size as the larva grew
larger. These young were probably the offspring of several females, as
four mature bees were found in the hole." The larva of an English
species hatches in ten days after the eggs are laid.
Another brood of bees appeared the middle of September, as on the ninth
of that month (1864) Mr. Emerton found several holes of the same species
of bee, made in a hard gravel road near the turnpike. When opened, they
were found to contain several bees with their young. September 2nd, of
this year, the same kind of bee was found in holes, and just ready to
leave the cell. It is probable that these bees winter over.
We have incidentally noticed the presence in the nests of Andrena and
Halictus of a stranger bee, clad in gay, fantastic hues, which lives a
parasitic life on its hosts. This parasitism does not go far enough to
cause the death of the host, since we find the young of the parasitic
Cuckoo bee, in cells containing the young of the former.
Mr. F. Smith, in his "Catalogue of British Bees," says of this genus:
"No one appears to know anything beyond the mere fact of their entering
the burrows of Andrenidæ and Apidæ, except that they are found in the
cells of the working bees in their perfect condition: it is most
probable that they deposit their eggs on the provision laid up by the
working bee, that they close up the cell, and that the working bee,
finding an egg deposited, commences a fresh cell for her own progeny."
He has, however, found two specimens of Nomada, sexfasciata in the cells
of the long-horned bee, Eucera longicornis. He also states, that while
some species are constant in their attacks on certain Halicti and
Andrenæ, others attack different species of these genera
indiscriminately. In like manner another Cuckoo bee (Coelioxys) is
parasitic on Megachile and Saropoda; Stelis is a parasite on Osmia, the
Mason bee: and Melecta infests the cells of Anthophora.
The observations of Mr. Emerton enable us still further to clear up the
history of this obscure visitor. He found both the larva and pupa, as
well as the perfect bee, in the cells of both genera; so that either
both kinds of bee, when hatched from eggs laid in the same cell, feed on
the same pollen mass, which therefore barely suffices for the
nourishment of both; or the hostess, discovering the strange egg laid,
cuckoo-like, in her own nest, has the forethought to deposit another
ball of pollen to secure the safety of her young.
Is such an act the operation of a blind instinct? Does it not rather
ally our little bee with those higher animals which undoubtedly possess
a reasoning power? Its _instinct_ teaches it to build cells, and prepare
its pollen mass, and lay an egg thereon. Its _reason_ enables it, in
such an instance as this, when the life of the brood is threatened, to
guard against any such danger by means to which it does not habitually
resort. This instance is paralleled by the case of our common summer
Yellow bird, which, on finding an egg of the Cow bunting in its nest,
often builds a new nest above it, to the certain destruction of the
unwelcome egg in the nest beneath.
In the structure of the bee, and in all its stages of growth, our
parasite seems lower in the zoölogical scale than its host. It is
structurally a degraded form of Working-bee, and its position socially
is unenviable. It is lazy, not having the provident habits of the
Working-bees; it aids not in the least, so far as we know, the
cross-fertilization of plants--one great office in the economy of nature
which most bees perform,--since it is not a pollen-gatherer, but on the
contrary is seemingly a drag and hinderance to the course of nature. But
yet nature kindly, and as if by a special interposition, provides for
its maintenance, and the humble naturalist can only exclaim, "God is
great, and his ways mysterious," and go on studying and collecting
facts, leaving to his successors the more difficult task, but greater
joy of discovering the cause and reason of things that are but a puzzle
to the philosophers of this day.
The larva of Nomada may be known from those of its host, by its
slenderer body and smaller head, while the body is smoother and more
cylindrical. Both sexes of Nomada imbricata and N. pulchella were found
by Mr. Emerton, the former in both the Andrena and Halictus nests, and
both were found in a single Andrena nest.
[Illustration: Wood Wasp.]