256 MODERN CLASSIFICATION OF INSECTS. 
they do not cast their skins. That this, however, is not the case, is 
evident, not only from analogy, but from an interesting specimen of 
Colletes succinctus in my collection, which I have represented in jig- 
90. 13., and in which the pupa is in the act of bursting through the 
dorsal skin of the larva; and it would seem as if the insect had not 
sufficient strength to enable it to make its escape, but that it remained 
alive in that position until the enclosed parts of the perfect insect had 
attained their ordinary colours, the thin skin with which they are 
covered being also scaled off in several places. 
Probably, no group of insects has attracted so much attention as 
the present, either amongst general observers or professed naturalists ; 
hence we find that the bees have afforded subjects for some of the 
most interesting memoirs which have hitherto been produced upon 
the insect tribes. Réaumur, De Geer, Huber, Latreille, and Kirby, 
have especially devoted themselves to the investigation of the habits 
and structure of these insects. The Monographia Apum Anglia of 
the last-named author may be cited as a model of a complete mono- 
graph. In it, and other more recent publications, about 250 species 
of bees found in Great Britain are enumerated. 
The classification of the Mellifera depends considerably upon the 
variations in the structure of the mouth; hence, and because the oral 
apparatus of the bec is perhaps one of the most interesting and com- 
plicated pieces of insect mechanism, I may perhaps be allowed to give 
a somewhat more extended notice of it*, selecting for illustration one 
of those species in which it is most fully developed, namely, the An- 
thophora retusa, and illustrating it minutely in various positions.¢ If 
* This account of the mouth of Anthophora retusa, and the subsequent obsery- 
vations upon the nature of the parasitic connection existing amongst certain bees, 
form the subject of a memoir read by me at the Entomological Society, on the Ist 
of December, 1834. 
+ Fig. 89. 1. represents the head of A. retusa, laterally, with the mandibles 
closing upon the extremity of the labrum, and the maxille and labium bent beneath 
the breast, as in inaction; jig. 89. 2. the head in front, with the latter organs 
in the act of being brought forwards; jig. 89. 3. the labrum detached ; fig. 89. 4. 
mandible of the female ; fig. 89. 5. ditto of the male; jig. 89. 6. profile of the head, 
with the labium and maxille partially unfolded and separated, showing the tubular 
mentum (m 2.) partially sheathed by the basal part of the maxille (m 1.) ; 
fig. 89. 7. shows the basal parts of these organs still more unfolded, to exhibit the 
manner in which the fulerum, K. (d), and the cardines, K. (dd), shut together, so as 
to lie between the lora, K. (y); jig. 89. 8. is a lateral view of the head, and lower 
parts of the mouth extended (the labrum and mandibles being removed); m x 
