EXTERNAL ANATOMY OF INSECTS. 4.99 
The sétuation of compound eyes differs in different 
tribes. In some, as in the Staphylinida, they are planted 
laterally in the anterior part of the head; in others, the 
Carabi, &c., in the middle ; in others again, Locusta, in 
the posterior part. In some, their station is more in the 
upper surface, either before or behind; so that a very 
narrow space separates them, or perhaps none et all. 
Instances of this position of the eyes occur in a minute 
weevil (Ramphus*), and many Diptera, &c. Of those 
that form an union on the top of the head, some are 
placed obliquely, so as to leave a diverging space below 
them, as in many Lzbellulina’, the drone’, &c. Others, 
as Atractocerus, in which the eyes occupy nearly the 
whole head, and unite anteriorly, have this diverging 
space above their conflux. In Rhzna barbirostris, another 
kind of weevil, they are confluent delow the head, at the 
base of the rostrum, and a very narrow interval separates 
them above. In a large number of the Heteromerous 
beetles, they are set ¢ransversely, in the Capricorn ones 
longitudinally. ‘Their surface, when they are lateral, has 
usually two aspects, one prone to see below, the other 
supine to see above. In general the eyes are situated 
behind the antennz, so that their position, whether it 
shall be anterior or posterior, depends upon that of those 
organs. Often, indeed, as in the last-named beetles, 
part of the eye is behind and part before the antenne ; 
but except where there are four eyes, as in Tetraopes, 
they are never placed before or below them. 
Though the eyes of insects are generally sessz/e, yet to 
give them a wider range they are sometimes, but it rarely 
* Ent. Helvet. i. t. xii. > Pirate VI. Fic. 10. 
© Kirby Jon. Ap. Angl. i. t. xi. Apis **, e. 1. f, 2. 
2K2 
