18 



ENTOMOLOGY. 



sometimes left in fine wet sand on the banks of streams or 

 by the seaside. 



In Fig. 16 the black dots are made by the fore, the clear 



Fig. 13.— Diagram of the knee-joint of a vertebrate (A) and an insect's limb (B). 

 a, upper, b, lower, shank, united at A by a capsular joint, at B by a folding 

 joint; d, extensor or lifting muscle; d 1 , flexor or lowering muscle of the lower 

 joint. The dotted line indicates in A the contour of the leg. — After Graber. 



circle by the middle, and the black dashes by the hind legs 

 (Graber). 



The wings are developed as folds of the integument, and 



Fig. 14. — Cross-section through the thorax of 

 a butterly. a b, muscles for raising, c d, 

 for drawing downward and inward, the less: 

 d, entothorax arising from the sternum. fc, 

 st: ny, wing-vein; g, fulcrum, or turning- 

 point; c h, muscles for lowering-, b f, for 

 raising, the wing; i k and m n. muscles for 

 lowering, lop, for raising, the dorsal plates. 



Fig. 15.- Diagram of muscles of 

 an insect's leg-. Besides the mus- 

 cles at the insertion <>f the limb 

 for raising and lowering it. in 

 the trochanter (tr) is a muscle 

 for rotating the leg ; «', for 

 stretching the tibia (tu>)\ n, flex- 

 or of tibia; o, flexor of the tar- 

 sus; m. retractor of the tarsus 

 and claws {cl).~ After Graber. 



