ANATOMY AND PHYSIOLOGY 



55 



as in Stenobothrus and such other Acridiidae as stridulate by 

 rubbing the femora against the tegmina. -'. 



Legs of Larvae. Thoracic legs, terminating in a single 

 claw, are present in most larvae. Caterpillars have, in addi- 

 tion, fleshy abdominal legs (Fig. 64) ending in a circlet of 

 hooks. Most caterpillars have five pairs of these legs (on 

 abdominal segments 3, 4, 5, 6 and 10), but the rest vary in 

 this respect. Thus Lagoa has seven pairs (segments 2-7 and 

 10 ) and Geometridae two (segments 6 and 10), while a few 

 caterpillars (Tischeria, Limacodes) have none. Larvae of 



FIG. 65. 



ec 



Mechanics of an insect's leg. a, axis of coxa; c, coxa; cl, claw; e, extensor of 

 tibia; ec, extensor of claw; et, extensor of tarsus; f, flexor of tibia; fc, flexor of 

 claw; ft, flexor of tarsus; r, r, rotators of coxa; s, spur; t, trochanter muscle (elevator 

 of femur) ; ti, tibia. After GRABER. 



saw flies (Tenthredinidae) have seven or eight pairs of abdom- 

 inal legs and larvae of most Panorpidae, eight pairs. Not a 

 few coleopterous larvae (some Cerambycidae, Phytonomus) 

 also have abdominal legs, which are incompletely developed, 

 however, as compared with those of Lepidoptera. 



The legless, or apodous, condition occurs frequently among 

 larvae and always in correlation with a sedentary mode of life; 

 as in the larvae of many Cerambycidae, nearly all Rhynchoph- 

 ora, a few Lepidoptera, all Diptera, and all Hymenoptera ex- 

 cept Tenthredinidae, Siricidae, and other Terebrantia. 



