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TEXT-BOOK OF ENTOMOLOGY 



membrane (membrana retinens, Fig. 593, mr), which is the stretched part of 

 the membrane around the rectum and in the anal legs, and which is intimately 

 associated with the rectal ligament. 



The structures in the chrysalis are, first, the cremaster, with its dorsal (Fig. 

 594, dcr) and ventral (t>cr) ridges, and the cremastral hook-pad (cAp), said by 



FIG. 593. Shrunken larval skin of Vanessa antiopa, cut open from the back and showing () 

 the retaining membrane, (rl) the rectal ligament, and (tl) the tracheal ligaments. 



Riley to be "thickly studded with minute but stout hooks, which are sometimes 

 compound or furnished with barbs, very much as are some of our fishing-hooks, 

 and which are most admirably adapted to the purpose for which they are 

 intended." 



FIG. 594. Ideal representation of the anal 

 8ubjoint of Vanessa antiopa, from behind, with 

 the spines removed, and all parts forced apart by 

 pressure so as to show the homologies of the 

 parts in the chrysalis which are concerned in 

 pupation : homologies indicated by correspond- 

 ing letters in Fig. 595, except that ; (the rectum ) 

 corresponds with pr in Fig. . r >!T>. 



Fio. 595. Anal parts of chrysalis of V- 

 nffixii (intiojxt, just prior to final extraction 

 from shrunken larval skin: c, en-master ; <!//>, 

 cremastral hook-pad : It, one of the hooks, more 

 enlarged ; rcr, ventral ercmastral ridge ; dcr, 

 dorsal cremastral ridge : fi'. larval rectum ; /</, 

 pupal rectum; ;y>. rectal plate; st\ sustentor 

 rid ges ; rnr, iiieiiiliriitin r<-titn-iin; rl. rectal 

 ligament ; //, traclieal ligament; the llth or 

 last spiracle-hearing joint and tlie 12th joint 

 being numbered. 



Secondly, there are the other structures, viz., the sustainers (sustentors\ 

 two projections which Riley states "homologize with the soles (plantce) of the 

 anal prolegs, which take on various forms (3), but are always directed forward 

 so as easily to catch hold of the retaining membrane." These sustentors are, 



