THE HIDDEN TYPE OF WING-GROWTH 139 



(p. 63) a specialized dorsal tail-region (or cremaster) (Fig. 33 cr) 

 armed with hook-like spines serves to fasten the pupa to its 

 silken cocoon or suspensory pad. 1 This cremaster is a modifi- 

 cation of the caterpillar's spiny suranal plate, lying dorsal to 

 the intestinal opening. After liberation from the larval 

 cuticle this cremaster is worked into the silken meshes so that 

 the pupa is safely anchored ; in the case of those butterfly 

 pupae which hang head downwards from a pad of silk those 



FIG. So. 



a, " Free " Pupa of primitive Moth (Ertocrania), ventral view ; 

 (td, mandible ; m, maxillary and I, labial palp). x 10. 

 After Packard, Mem. Nat. Acad. Sci. VII. b, " Incomplete " 

 Pupa of clothes moth (Tinea), side view, x 8. In part after 

 Packard. 



of the brightly-coloured " Red Admiral," " Peacock," and 

 other of our native vanessids for example the cremaster thus 

 becomes an essential means of support. 



Some interesting transitional conditions between the typical 

 free and obtect pupae can be observed among insects of various 

 groups. Thus in the pupa of some two-winged flies (Diptera), 

 while the head-appendages and wings are adherent to the 

 body, the legs are free. Moths of the more primitive families 



1 W. Hatchett Jackson : " Morphology of the Lepidoptera ". Trans. 

 Linn. Soc. Zool. (2), Vol. V., 1890. E. B. Poulton : " External Morphology 

 of the Lepidopterous Pupa ". T. c. 1898. 



