

ANATOMY AND PHYSIOLOGY 51 



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 

 saw flies (Tenthredinidae) have seven or eight 

 pairs of abdominal legs and larvae of most 

 Panorpidae, eight pairs. Not a few coleopter- 

 ous larvae (some Cerambycidae, Hyper a) also 

 have abdominal tubercles that represent legs, 

 but are incompletely developed as compared 

 with those of Lepidoptera. 



The legless, or apodous, condition occurs 

 frequently among larvae and always in correla- 

 tion with a sedentary mode of life; as in the 

 larvae of many Cerambycidae, almost all Rhyn- 

 chophora, a few Lepidoptera, all Diptera, and FIG. 65. Foot of honeybee, 



f^ ' ,. ., ' .. Apis mellif era. c, c, claws; p, 



all Hymenoptera except Tenthredinidae, Sirici- puiviiius; *>-/, tarsai seg- 

 dae, and other Terebrantia. ments.-After CHESHIRE. 



Among adult insects, female scale insects are exceptional in being 

 legless. 



Walking. An adult insect, when walking, normally uses its legs in 

 two sets of three each ; thus the front and hind legs of one side and the 



p K 



FIG. 66. Caterpillar of Protoparce sexta. Natural size. 



middle leg of the other move forward almost simultaneously though 

 not quite, for the front leg moves a little before the middle one, which, 

 in turn, precedes the hind leg. During these movements the body is 

 supported by the other three legs, as on a tripod. The front leg, 

 having been extended and its claws fixed, pulls the body forward by 



