THE COMPOUND EYES. 11 



These organs are divided into two parts - namely, the 

 scape, or long joint nearest the head, Fig. 2a, and the 

 club, 2b. This latter portion is subject to most extra- 

 ordinary variations of form, as will be seen in the 

 following pages. 



The head itself is shown at Fig. 5, the upper 

 surface being here given. $aa are the eyes, %b the 

 vertex, or crown of the head, ^c is the occiput, or 

 back of the head ; and $d the clypeus, or shield, 

 which covers the actual mouth. Fig. 6 shows the 

 under side of the head. 6aa are the eyes, 6b the 

 insertion of the antennae. 



As reference has been made to the eyes, it must 

 be mentioned that these organs, although apparently 

 only two in number, are in reality compound eyes, 

 being made of a vast number of facets gathered into 

 two groups, one on each side of the head. There is 

 an apparent exception to this definition in the well- 

 known Whirligig Beetles (Gyrini), which appear to 

 have four eye-groups, two above and two below. 

 This exception is, however, more apparent than real ; 

 the eye-groups being in fact only two, but each pair 

 being crossed by a band of the horny material of 

 which the outer skeleton is composed. The com- 

 pound eyes can be seen to great perfection in some 



8a. Sternum. 8/>. Insertion of coxse. 9. Meso-thorax and upper surface of 

 abdomen. ga. Mesothorax alone. 9^. Abdomen, upper surface alone. 10. 

 Metasternum and abdomen. iort. Metasternum alone. io. Abdomen, under 

 surface alone. loc. Parapleura, or side pieces. ic*/. Episterna, or breast pieces. 

 12. Scutellum. 



Legs. n. Anterior, or first pair of legs. n. Tarsi, or feet. n3. Tibia, or 

 shank. i\c. Femur, or thigh. i\d. Trochanter. \\e. Coxa. 13. Inter- 

 mediate pair of legs. 15. Posterior pair of legs. 



The lyings. 14. Elytra. 14^. Suture. 14^. Lateral margin. 14^. Apex. 

 i4</. Rase. 14^. Di.c. 16. Wings folded on abdomen. 17. Left wing ex- 

 panded. 18. Right wing 'olded. 



