180 THYSANOURA. 



these voracious maggots, in that space of time increase in 

 weight two hundred fold, and that they are further capable 

 of giving birth in a short time to other insect legions, we 

 perceive at once their adaptation to the important duty 

 thus intrusted to them. 



The Spider Flies (Hippoboscd) * are parasitic, and, 

 strange to say, their females give birth to pupce instead 

 of eggs or larvce, hence they have been designated Pupi- 

 para."\ These pupaB are of considerable size, and at first 

 very soft, but their skin soon hardens into a pupa-case. 

 These insects are remarkable from having no wings. 

 Some of them inhabit the nests of birds, and live by 

 sucking the blood of the little nestlings, whose warmth 

 contributes to their development. 



The Forest Fly (Hippobosca equina) is notorious for 

 its incessant attacks upon horses ; and in some districts 

 appears in great numbers. Another species conceals 

 itself in the wool of sheep, from which animals it derives 

 its food ; and there are some not furnished with wings, 

 that are exclusively resident in the hair of bats. 



ORDER THYSANOURA.J 



These insects are without wings, and undergo no 

 metamorphosis ; they are 

 distinguished by the pos- 

 session of peculiar in- 

 struments of locomotion, 

 appended to the extre- 

 mity of their abdomen. 

 (Fig. 141.) The order in- 

 cludes but two genera, the 

 Sugar-lice and the Spring- 

 tails. 



Sugar-lice (Lepisma) 

 have a row of filaments 

 attached to the hindmost ring of the body, three of which 

 are of considerable length, and by their assistance the 

 Lepisma leaps into the air. Their legs are short, but 



* t TTTTOS, hippos, a horse ; <fo-/c<o, bosco, to feed on. 



f Pupa, a pupa ; pario, 1 bring forth. 



j Ovo-avos, thysanos, a tuft ; ovpd, oura, tail. 



