of the Oil Beetle, Meloë. 355 
tion from a carnivorous to a truly vegetable-feeding insect, the transition itself 
being in reality gradual, like the change which takes place in the form of its 
manducatory organs. The manner in which the change in the structure of 
these parts is effected, and the slender, jointed, unguiculated, pediform organ 
of the young larva, fitted only for piercing and for prehension, is altered to 
the short, obtuse, and powerful jaw, is by the relative sbortening, consolida- 
tion, and anchylosis of the coxal, femoral, and tibial divisions of the pediform 
mandible, whilst the long claw-like and acute apex is deciduated and entirely 
thrown off as a portion of the tegument at the next change of skin. This 
relative shortening is continued throughout the metamorphoses, and in this 
way the organ is gradually more and more altered in structure ( fig. 9), is fitted 
for a new function, and is adapted for a complete change in the habits of the 
imago. 
A general correspondence in structure thus seems to indicate similar corre- 
spondence in habit and function. "Those families of insects which are most 
nearly allied in organization approach the most nearly to each other in their 
economy. But they differ from each other in the divergence of their particu- 
lar habits or instincts from one general character, according as the structures 
which minister to those habits or instincts depart from the common type of 
formation. The larva of Sitaris, in the general conformation of its body, re- 
sembles that of Meloë, and both, as we have seen, are parasitic in their habits 
in the nests of the same genus of insects ; but they differ in their special eco- 
nomy as well as in particular details of structure. All we yet know of the habits 
of Horia shows that this family also is parasitic in its larva state in the nests 
of the carpenter-bee. The perfect insect has long been known to be allied 
in general structure to the perfect Meloé, and I have little doubt that it 
approaches closely to that of Meloë and Sitaris in the early stage of its larva, 
The drawing given by the Rev. L. Guilding of the advanced stage of the larva 
of Horia, and the fact that Mr. Guilding's specimen has six short legs, so 
closely agree with the advanced stage of Meloé, that we may fairly regard the 
general form of the larva in the earlier stages of these two insects as similar, 
and conclude that Horia, Sitaris and Meloé all at first are parasitic on the 
bee-larva. 
VOL. EL, es 3 A 
