Fig. 593.—Shrunken larval skin of Vanessa antiopa, cut open from the back and showing (mr) the retaining membrane, (rl) the rectal ligament, and (tl) the tracheal ligaments.
The structures in the chrysalis are, first, the cremaster, with its dorsal (Fig. 594, dcr) and ventral (vcr) ridges, and the cremastral hook-pad (chp), said by 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 subjoint 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 corresponding letters in Fig. 595, except that r (the rectum) corresponds with pr in Fig. 595.
Fig. 595.—Anal parts of chrysalis of Vanessa antiopa, just prior to final extraction from shrunken larval skin: c, cremaster; chp, cremastral hook-pad; h, one of the hooks, more enlarged; vcr, ventral cremastral ridge; dcr, dorsal cremastral ridge; lr, larval rectum; pr, pupal rectum; rp, rectal plate; sr, sustentor ridges; mr, membrana retinens; rl, rectal ligament; tl, tracheal ligament; the 11th or last spiracle-bearing joint and the 12th joint being numbered.
Secondly, there are the other structures, viz., the sustainers (sustentors), two projections which Riley states “homologize with the soles (plantæ) 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, however, as Jackson[[111]] has shown, and as we are satisfied, the vestiges of the anal legs.
Fig. 596.—A, chrysalis of Terias. B, posterior end of chrysalis of Paphia. C, posterior end of chrysalis of Danais. E, one of the sustainers of Terias, greatly enlarged to show its hooked nature. All the parts of subjoint lettered to correspond with Fig. 595.