EXTERNAL ANATOMY OF INSECTS. 437 
versatile head, the occiput forms an angle with the vertex, 
often rounded, and sometimes acute. This structure 
may be seen in Latreille’s Trachelides, and several other 
beetles. In the Hymenoptera, Diptera, and others with 
a versatile head, the part now under consideration curves 
inwards from the vertical line, sc as with the temples and 
under parts of the head to form a concavity adapted to 
its movement upon the trunk. 
vi. Gene *.—The cheeks of insects (Gene) usualiy sur- 
round the anterior part of the eyes, and lie between them 
and the mandibles or their representatives. Where 
they approach the latter, as in the Predaceous beetles 
( Adephagana), they are very short, and of course longer 
where the eyes are further removed from the mouth ; 
as in the weevils (Rhyncophora), where they form the 
sides of the rostrum, and often contain a channel which 
receives the first joint of the antennee, when they are 
unemployed. In the Scarabaide and many other La- 
mellicorn beetles, their separation on each side from 
the nose is marked by a ridge; and in the wasps (Vespa) 
by an impressed line or channel. In an African genus 
Gnathocera‘, to which Cetonia bicornis and vitticollis 
belong, the cheeks are porrected on each side of the 
mouth into a horizontal horn. These horns have at 
first the aspect of a pair of open mandibles. In the 
magnificent Golzath7, the horns of the male are rather a 
process of the cheek than of the nose. In Alurnus, Aispa, 
and other beetles, these parts, by their elevation and 
conjunction with the lower side of the head, form a kind 
of fence which surrounds and protects the oral organs ; 
* Pirates VI. VIL. f. > Prave XXVII. Fie. 4. f 
Linn. Trans. xiv. 57). 
