

Eruciform Larvae. Tin- prevalent type d larva among bol< 

 oloua inserts is thi /. illustrated I-;. :i!lar 



IIcr<- the body i- ( \ lindrit ;il ;IIK| <>Mni flefthyj ' be i 



iiincn! weak; the legs, anteu and mouth part- redu< 



to disappearance; tin- habits sedentary ami Hi' 



spondingly reduced. These eharacterisl interpreted as being 



result- <>f partial or entire disuse, the amount o! re<lii(tion b< 

 portional to tin- decree of inactivity. Kxtreme rrdin tion n the 



OtS of parasitic and Mich other Diptrra as, -<. uring their food with 

 almost no exertion, arc simple in form, thin-skinned, legless, with only 

 a mere vestige of a head and with sensory powers of but the simplest 

 kind. 



Transitional Forms. The cruciform is dearly derived from the 



A U 



' mtispa. /I, larva at hatching thy sanun form; B, same larva just before 

 first molt now becoming cruciform. C, imago, the wings omitted; D, winged imago, 

 slightly enlarged. A and B after BRAUER; C and D after EMERTON, from Packard's Text- 

 Book of Entomology, by permission of the Macmillan Co. 



thysanuriform type, as Brauer and Packard have shown, the continuity 

 between the two types being established by means of a complete series 

 of intermediate stages. The beginning of the cruciform type is found 

 uroptera, where the campodeoid sialid larva assumes a quiescent 

 pupal condition. The key to the origin of the complete metamorpho- 

 sis, involving the eriu iform condition, Packard finds in the neuropterous 

 tieiuis Mtintispii i Fig. 214), the first larva of which is truly campodei- 

 form and active. Beginning a sedentary life, however, in the egg-sac of 

 a spider, it loses the use of its legs and the antennae become partly 

 aborted, before the first molt. In Packard's words. "Owing to this 

 change of habits and surroundings from those of its active ancestors, it 



