We have up till now found the insects of the great family of bees
collected together in perfectly organised societies. But there are a
great number of species of this family which live alone. We will
briefly mention the most interesting of them.
The females of the solitary bees are impregnated like those of the
humble bees, and lay in spring, after having passed the winter asleep.
They build a nest divided into cells, fill it with eggs, and with a
honied paste shut it up, and die, without having seen their progeny
hatched.
[Illustration: Figs. 336, 337, 338.--Anthophora parietina.]
[Illustration: Fig. 339.--Carpenter Bee, Pupæ, Eggs, Galleries, and
Nests.]
The _Anthophoras_ (Figs. 336, 337, 338) resemble bees, but they are
more hairy, and of greyish colour. Their nest, composed of earth
tempered and agglutinated with their saliva, is made in the cracks of
old walls or in the ground. It has the form of a twisted tube, and is
divided, by partitions, into compartments, each of which is to receive
a larva. Each insect, when hatched, pierces its own wall, and profits
by the hole of exit of the brother which preceded it.
[Illustration: Fig. 340.--Mason Bee and Nest.]
These insects do not live together in societies. Indifferent
neighbours, they do not lend each other mutual assistance. They have
their parasites, the _Melactas_, like the humble bees. These parasites
are hairy, blackish insects, spotted with white, laying their eggs in
the nests of the _Anthophoras_, which permit them to do so, and, at
the expense of their own progeny, bring up the intruder's little ones.
The Carpenter Bee, or Wood-piercer (_Xylocopa_), hollows out
galleries in decayed wood, and builds in them cells placed one over
the other--a work often occupying many weeks. She then furnishes the
bottom of the cell with pollen mixed up with honey, lays an egg in the
middle of this paste, and closes the cell by a ceiling of saw-dust
agglutinated with saliva. On this ceiling she establishes a new cell,
and so on, right up to the orifice, which she closes in the same
manner. Réaumur is astonished, with reason, at the admirable instinct
which makes this provident mother determine the exact quantity of
nourishment which will be necessary for its larva. When this has
absorbed all its provisions, it alone quite fills up its cell, and
changes into a pupa. It is worthy of remark, that the head of the
young is always turned downwards, in such a way that it is by the
bottom of its cell that it comes out. The bottom of the first is very
near the surface of the wood, so that the insect it encloses has only
a thin layer of wood to pierce through in order to set itself free.
Each one of those which are born next has only to pierce the floor of
its hiding-place to find the road before it free. The _Xylocopæ_ pass
the winter in the pupa state, and the perfect insects, with wings of a
beautiful metallic violet, appear in the spring, but are not found in
this country.
[Illustration: Fig. 341.--Interior of the Nest of the Mason Bee.]
Other solitary bees have their hind legs unsuited for the gathering of
pollen, but have the rings of the abdomen furnished with hairs for
that purpose. Such are the Mason Bees of Réaumur, belonging to the
genera _Osmia_ and _Chalicodoma_,[98] which build their nests against
walls with tempered earth, which become very hard.
[98] At a meeting of the Entomological Society of London, Feb.
18th, 1867, Mr. Newman exhibited the lock of a door, one of
several which in 1866 were found at the Kent Waterworks,
Deptford, to be completely filled and choked up with nests of
_Osmia Bicornis_: a portion of the nest had been forced out by
the insertion of the key. The locks were in pretty constant
use, so that the nests must have been built in the course of a
few days.--_Journal of Proceedings of the Entomological Society
of London_, 1867, lxxvi.--ED.
[Illustration: Fig. 342.--Rose Megachile (_Megachile centuncularis_).]
These nests (Figs. 340 and 341) are filled with cells of oblong form
arranged irregularly. At first sight they might be taken for little
lumps of earth plastered against the wall. When the perfect insect
emerges, it is obliged to soften the mortar with its saliva, and to
remove it, grain by grain, with its mandibles. The nests of
_Chalicodomas_ are common in the environs of Paris, on walls of rough
stones exposed to the south. They are often to be found in the parks
of Meudon, of Conflans, of Vésinet, &c.
The Leaf-cutting Bees (_Megachile_) are not less worthy of remark in
their habits. These insects make their nests in tubes lined with the
leaves of the rose, the willow, the lilac, &c., placed in a
cylindrical burrow. Each nest contains generally from three to six
cells, separated by partitions of leaves. They cut off the pieces of
leaves they require with their mandibles, the notches being
wonderfully cleanly cut, as if they had been done with a punch.
They make as many as eight or ten envelopes in succession with the
leaves, which, as they get dry, contract, keeping, however, the form
given to them by the insect. The cells destined to receive the eggs
acquire thus a certain solidity. Fig. 342 represents the nest of the
Megachile.
[Illustration: Fig. 343.--Gallery of an _Andrena_.]
The Upholsterer Bees (_Anthocopas_) line their nests with the petals
of flowers, as, for example (_Papaver rhæas_), the corn-poppy. Their
burrows are made perpendicularly in the beaten earth of roads, and
each contains one solitary cell, lined with portions of petals. When
the egg has been laid at the bottom of this cell, the bee fills up the
rest of the hole with earth, to hide it from notice.
The Mining Bees (_Andrenæ_) hollow out in the ground tubular galleries
(Fig. 343). They are not larger than ordinary flies. A great number of
other bees are known, but their habits are little understood, and we
shall not occupy ourselves about them.