THE CREMASTER 



639 



however, as Jackson 1 has shown, and as we are satisfied, the vestiges of the 

 anal legs. 



Thirdly, the susteiitor ridges, which, as Riley states, may be more or less 

 obsolete in some forms, in Paphia (Fig. 596, J5) and Liiuenitis form "quite 



FIG. 596. 4, 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. 



a deep notch, which doubtless assists in catching hold of the larval skin in the 

 efforts to attach the cremaster." 



" It is principally," adds Riley, " by the leverage obtained by the hooking of 

 the sustainers in the retaining membrane, which acts as a swimming fulcrum, 



FIG. 597. Pupation of butterflies : a, attachment of larva of Danais archippus ; p, attach- 

 ment of larva of Paphia glycerium ; b, ideal larva soon after suspension ; d, ideal larva a few 

 hours later, the needle (n) separating the forming membrane from the sustainers ; I, ideal larva 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 the 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 ; ap, anal plate ; Ir, larval 

 rectum ; pr, pupal rectum ; mr, retaining membrane ; c, cremaster ; s, sustainers. This and 

 Figs. 593-596 after Kiley. 



1 In his remarkable studies on the morphology of the Lepidoptera, Professor W. 

 Hatchett-Jackson states his belief that Riley's homology of the sustentors with the 

 soles or plantre of the anal prolegs, and the sustentor ridges with their limbs, is 

 wrong, and that the eminences on either side the anal furrow, or the "anal promi- 

 nences," as they are termed by Riley, represent the prolegs, and that the sustentor 

 ridges and sustentors are probably peculiar developments of the body of the 10th 

 somite, found only in some Lepidoptera. From our examination of pupa of different 

 families of moths, we are satisfied that Jackson's view is the correct one. We have 

 not found the sustentors and their ridges in the pupae of the more generalized moths, 

 but the vestiges of the anal legs are almost invariably present, their absence in the 

 pupa of Nola and Harrisina being noteworthy. 



