io8 The Life-History of Insects 



tion, however, can be traced in the structure of 

 different eruciform larvae. The grubs of most Saw- 

 flies are caterpillars like those of moths, but there are 

 from six to eight pairs of prolegs present ; in moth- 

 caterpillars there are hardly ever more than five 



pairs, while 

 in some cases 

 there are 

 only two 

 pairs, those 

 on the sixth 

 and ninth 

 segments of 

 the hind- 

 body. In 

 the grubs of 

 Flies, legs 

 like the 

 thoracic 

 limbs of the 

 c a terpillar 

 are entirely 

 wanting. In 

 some cases — 

 the "rat- 

 tailed grub " 

 of the Drone- 

 fly for ex- 



FlG 



, 68. — a. Full-grown Maggot of Housefly (ISInsca 

 domcstica), magnified 5 times ; /■. fan-shaped closed 



spiracle on first body-segment ; c. head-region pro- a m D 1 C 1 h e 



traded ; li. tail-segment showing functional spiracles; 

 e. head-region from side ; _/C from above showing hook- 

 jaws ; g^. head of young maggot, from above ; h. egg. 

 b. — h. more highly magnified. From Howard, Bull. 

 4 (n.s.) Div. Ent. U.S. Dept. Agr. 



insect crawls 

 by means of 

 seven pairs 

 booklets like 

 all traces of 



of circular sucker-feet, provided with 



those of the caterpillar's prolegs. Or 



limbs of any kind may disappear and the grub become 



a maggoty like the offspring of the House-fly (fig. 68) 



