488 EXTERNAL ANATOMY OF INSECTS. 



versatile head, the part now under consideration curves 

 inwards from the vertical line, so as with the temples and 

 under parts of the head to form a concavity adapted to 

 its movement upon the trunk. 



vi. Gence a . — The cheeks of insects (Gence) usually 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 (Cicin- 

 dela, Carabus L. &c), they are very short, and of course 

 longer where the eyes are further removed from the 

 month; as in the Rhyncophorous beetles [Curculig L.), 

 where they form the sides of the rostrum, and often con- 

 tain a channel which receives the first joint of the anten- 

 nas, when they are unemployed. In the Scarabceidce and 

 many other Lamellicorn beetles, their separation on each 

 side from the nose is marked by a ridge b ; and in the 

 wasps (Vespa) by an impressed line or channel. In an 

 African tribe at present arranged with Cetonia F., to 

 which C. bicomis Latr. c and another, which he has named, 

 I believe, C. 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 Goliathi Lam., the horns of the male 

 are rather a process of the cheek than of the nose. In 

 Alurnus, Hispa, 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 ; in many Cimicidce, by a similar eleva- 

 tion of the cheeks, the bed of the promuscis is formed. 



1 Plates VI. VII. f. h Plate XXVII. Fig. 4. f. 



c Cuv. Regne Animal iii. t, xiii f. 4. 



