264: MODERN CLASSIFICATION OF INSECTS. 
ones being 4-jointed, and resembling the maxillary, which have always 
six joints. The mandibles are simple, or terminated by one or two 
notches (fig. 90. 5. mand. of A. armata g ). The antenne are 
elbowed (fig. 90. 6. antenna of Andrena $); the hind legs ( fig. 
90. 7. hind leg ?, 8. ditto ¢ Andrena) are generally completely 
clothed with hairs; the trochanters and femora in the females being 
pollinigerous; the basal joint of the posterior tarsi is never externally 
dilated into an angle, and the second joint of the tarsi arises from the 
centre of the lower edge of the preceding joint. 
These insects are all solitary, each species consisting only of males 
and females. The latter collect pollen from the stamens of flowers, 
rather by means of the general hirsuties of the body than with the 
posterior tarsi. This they form, by the addition of a little honey, into 
a paste for the food of their progeny. They burrow in the ground, 
often to a considerable depth, in sandy situations; sometimes even 
upon foot-paths, especially if exposed to the sun. At the foot of 
these burrows they deposit an egg in the midst of a supply of this 
paste sufficient for the entire consumption of the future grub, and 
which is then covered up: they thus proceed, cell after cell, each 
being of the width of the burrow, closing up the hole at the top with 
earth, to prevent the attacks of parasites, which, however, often succeed 
in entering the hole, and depositing their eggs in the cells. Some 
species, however, are parasites upon the others, the nature of whose 
economy I have already detailed. 
In the structure of the mouth, some of these insects are nearly 
related to certain burrowing wasps, as Crabro, Philanthus, &c.: with 
these, therefore (forming a first division, which may be termed Obtusi- 
lingues), the arrangement of the bees is commenced; and in which the 
central portion of the labium is obtuse, being either transverse or 
heart-shaped, and very short (fig. 90. 20. labrum of Colletes). This 
division comprises only two genera, both of which are British. 
The species of Hylaeus (which as a genus has been greatly confused 
by Fabricius) have naked bodies, and are consequently destitute of 
apparatus for carrying pollen, and are stated by St. Fargeau (Ane. 
Méth. tom. x. p. 213.) to be parasitic upon other Mellifera (fig. 90. 21. 
hind leg 9). They are generally found in the flowers of various 
species of Reseda; I have also observed them repeatedly in those of 
the onion. They emit, when handled, a strong, yet agreeable odour, 
resembling the scent of balm, or rather Dracocephalum Moldavicum. 
