THE COCOON-BREAK /; li 



633 



tera, and in Micropteryx (Fig. 588), the jaws used by the pupa for 

 cutting its way out of the cocoon are even larger in proportion than 

 in the pupa of caddis-flies (Fig. 588), being of extraordinary size. 



In Myrmeleon the pupa 

 pushes its way half out of 

 the cocoon, and then re- 



mx. p 



FIG. 588. Mandibles (md) of Micropteryx purpuriella, enlarged. Author del. A, pupal 

 head of a hydropsychid caddis-fly, showing the large mandibles. After Keaumur, from Miall. 



mains, while the imago ruptures the skin and escapes (Fig. 589, a). 



Thus in the Neuroptera and Trichoptera we have already estab- 

 lished the more fundamental methods of escape from the cocoon, 

 which we see carried out in various ways in the more generalized 

 or primitive Lepidoptera. 



The most primitive method in the Lepidoptera of escaping from 

 the cocoon seems to be that of Micropteryx. 



"In this genus," says Chapman, "though it is nominally the pupa that 

 escapes from the cocoon, it is in reality still the imago, the imago clothed in the 

 effete pupal skin. To rupture the cocoon it uses not its own jaws, but those of 



FIG. 589. Larva of Myrmeleon with (a) its cocoon and cast pupa-skin. 



the pupal skin, energizing them, however, in some totally different way from 

 ordinary direct muscular action, their movements being the result of the ver- 

 micular movements of the pupa, acting probably by fluid pressure on the articular 

 structure of the jaws, by some arrangement not altogether different perhaps 

 from the frontal sac of the higher Diptera. In the Micropteryges the jaws of 

 the pupa not only rupture the cocoon, but appear to be the most active agents 

 in dragging the pupa through the opening in the cocoon and through any super- 

 incumbent earth, being merely assisted by the vermicular action of the abdomi- 



