164 



THE AMERICAN ENTOMOLOGIST. 



/igament {Figs. 66, 68, r/) or shed intestinal 

 canal; 3d. The Osborne or retaining mem- 

 brane {ynembrana retinens, Figs. 66, 68, mr), 

 which is but a stretched and specialized 

 part of the mucous membrane* that accu- 

 mulates around the rectum and in the 

 anal prolegs, and that is intimately con- 

 nected with the rectal ligament. 



In the second category we have certain 

 structural features of the chrysalis. (See 

 Figs. 68, 69, where corresponding parts are 

 similarly lettered.) These are: 



First. The cremaster proper (r), which 

 is the homologue of the anal plate of the 



Shrunken larval skin of Vanessa antio/>a^ cut open from the back, and 

 showing (mr) the retaining membrane, (r /) the rectal ligament and (^ /) 

 the tracheal ligaments (after Riley). 



larva, and the form of which is fore- 

 shadowed in that of said anal plate. This 

 cremaster assumes a great variety of dif- 

 ferent forms, but in general may be said 

 to be a tapering piece, more or less incurved 

 ventrally, and having the ventral and dorsal 

 margins thickened or ridged, and these 

 ridges may be respectively called the vett- 

 tral and the dorsal cremastral ridges {v c r 

 and^^r). This cremaster is surmounted 

 at the apex and sometimes along the ven- 

 tral ridges by what may be called the 

 cremastral ho ok-pad {c hp), thickly studded 



* I designate by this name the colorless lining of the larval 

 skin that separates from the forming chrysalis. If, as recent 

 physiological research indicates, it is only the outer half of 

 the outer or epidermic layer of tho skin (cuticula of modern 

 histologistf) which is cast off in the exuviation of inverte- 

 brates, then this mucous lining is developed between the two 

 separating layers of said cuticula. 



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. 68, /i.) 



Secondly. We have the sustainers {siis- 

 tentores), two projections which homologize 

 with the soles {plantce) of the anal prolegs, 

 and which take on various forms [s), but 

 are always directed forward, so as to 

 easily catch hold of the retaining mem- 

 brane. In the yellow butterflies (as Caly- 

 drias, Terias, Colias), where the body of the 

 chrysalis is so thrown 

 back that mere 

 projecting tubercles 

 would not suffice, we 

 find them transformed 

 into actual hooks (Fig. 

 6g,A, s and E) ; while in 

 some of the succincti 

 they are little more than 

 a thickening of the an- 

 terior margin of the 

 subjoint. In all Lepi- 

 dopterous pupae these 

 remnants of the anal 

 prolegs are more or 

 less indicated, while in 

 certain moths [Ptero- 

 phorid(£), where the pu- 

 pa is partly suspended 

 as it is in the Nympha- 

 lidce, they are covered with long hooks simi- 

 lar to those at the tip of the cremaster 

 and to those which, in the larva, armed 

 the hind plantae. 



Thirdly. We have what may be called 

 the sustentor ridges (x r) usually connected 

 with the sustainers, and embracing them 

 on the outside, and extending backward 

 to the inside of the ventral cremastral 

 ridges, and sometimes, as in Paphia (Fig. 

 69, B) and Limenitis, there forming quite a 

 deep notch, which doubtless assists in 

 catching hold of the larval skin in the 

 efforts to attach the cremaster. These 

 sustentor ridges are homologous with the 

 limb of the anal prolegs, and the exposed 

 edge with the posterior border of said 



