i66 



THE AMERICAN ENTOMOLOGIST. 



abundantly proved, at least ten or twelve 

 times the weight of the chrysalis ; while it 

 will support, if held by the larval skin, 

 several times the weight of the chrysalis, 

 before separating therefrom. E.xperimen- 



and always intimately connected with and 

 forming but a branch of the rectal ligament. 

 When extended from its attachments, as 

 when the chrysalis rises to the silk, this 

 membrane dries, and in the cast-off larval 



[Fig. 69.] 



A, chrysalis of Terias : B^ posterior end of chrysalis of Paphia ; C, do. of Danais : E, one of 

 the sustainers of Terias, greatly enlarged to show its hooked nature ; all the parts of subjoin! let- 

 tered to correspond with the same parts in Fig. 68 (after Riley). 



tal proof is easily obtained by pinning the 

 larval skin, which has been flayed from the 

 chrysalis, to a small piece of cork and then, 

 while grasping the chrysalis as indicated, 

 sticking additional pins in the cork, until 

 the increasing weight breaks the ligament. 



skin retains, more or less perfectly, the 

 stretched form. If the mucous membrane 

 of the larva was thick and strong, as in 

 Vanessa, the dried membrane will be broad, 

 with two indentations where it was held by 

 the retainers; if more delicate, as in Danais, 



[Fig. 70.] 



Pupation of Butterflies :— a, attachment of \3.rv2ioi Danais archippus : p,do.o{ Pafi/iia rlycerium .- 

 b Ideal larva soon after suspension ; d, do. a few hours later, the needle (n) separating the forming membrane from 

 the sust.-iiners ; e, do. just before splitting of larval skin, with retaining membrane loosened from the sustainers 

 and showing Its connection both with the larval and pupal rectum. In all the figures the joints of body are 

 numbered ; the forming chrysalis is shaded in transverse lines ; the intervening space between it and larval skin 

 IS dotted ; h is the hillock of silk ; hi, hooks of hind legs ; a/, anal plate ; /r, larval rectum ; /r, pupal rectum ; 

 mr. retaining membrane ; c, cremaster; s, sustainers (after Riley) . .r .- .- , 



In brief, the retaining membrane is that 

 part of the inner larval skin surrounding 

 the prolegs, drawn down by the sustainers, 



Paphia, or Apatura, the dried membrane 

 is more forked, showing how the retainers 

 have acted upon its elasticity. In every 



