i So 



\V. L. TOWER. 



ula and the new to help form the exuvial fluid. Eventually 

 nearly all of the contents of the glands are extruded, leaving 

 them small and shrunken as shown in Fig. 3, A. 



After ecdysis and especially after pupation the degeneration of 

 these glands is rapid, as shown in Fig. 3, the cell speedily return- 

 ing to a normal hypodermal cell in size and ultimately it breaks 

 down completely. 



As far as I can discover these glands are exactly like those 

 found by Gonin in Pieris brassiac, and I have observed the same 

 structure in Pieris rape? and frotodice, and Clisiocampa aincri- 

 cana among the Lepidoptera and they are widespread in the 



B C 



FIG. 3. L. dedmlineata. Three stages in the degeneration of the exuvial glands. 

 A, gland immediately after ecdysis ; B, stage of gland during the period of recon- 

 struction ; C, gland nearly reduced to normal hypodermal cell in period of growth. 



Chrysomelidae and Coccinnellidae, especially in the tropical species. 

 Nowhere have I found these unicellular glands in larvae that live 

 in burrows, or in the soil or in cells, but only in larvae living 

 freely exposed upon plants where there exists the greatest liability 

 to rapid desiccation. In L. dedmlineata, innltitccniata and their 

 tropical allies these glands developed in the embryo in small 

 numbers over the entire body surface and are active at each ecdy- 

 sis. As the larva grows, however, the number of these glands 

 increase until at the time of pupation there are very many of them 

 scattered over the body, but they are most numerous upon the 

 pronotum. During the pupal period nearly all degenerate rap- 

 idly and but few are functional at the final transformation. 



These glands and their increase in number is, I believe, an 

 adaptation in these freely exposed larvae, to enable them to pass 

 with the least mortality through such critical periods of their life 

 as ecdysis and pupation. I can see no reason why this adapta- 



