454 E, A. ANDREWS 



quent vertical columns in which the same cuticular substance is 

 continuous from the upper to the lower shell of the elytron. 

 These columns are the above red dots. 



The exoskeleton, or shell of the lower surface, is thin and made 

 up, for the most part, of several parallel layers or laminae, of 

 which the outermost differs but little from the inner ones, but 

 bears numerous fine, oblique spinules, and in some parts of the 

 elytra, long setae. 



The upper exoskeleton is very thick, and plainly of two por- 

 tions, the inner like that of the lower surface, but thicker; and 

 the outer of dark dense material, yellow-red in sections. It is 

 this outer part of the shell that gives the dark red color to the 

 beetle as seen from the outside. This outer layer is not, how- 

 ever, all alike in structure, but is in turn divided into a thicker 

 inner and a very thin outer portion, the latter only 8 ju in thickness. 



When the section is allowed to dry out, the shell changes to 

 light color but this change is only in this thin outermost lamina. 

 Where the shell has naturally red spots, the dry shell still pre- 

 serves these spots and the section shows that here, again, the 

 outermost lamina is the only part that is responsible for this 

 difference in color. The outermost lamina does not lose its dark 

 color in the region where natural spots are found. 



The substance of this color-determining lamina is seen, under 

 the immersion lens, to be penetrated vertically by pores or slits 

 or some lack of continuity at intervals measured as about 0.6 /x. 

 Where the dark red spots of the shell occur, the lamina seems more 

 homogeneous, as if infiltrated with some material that filled its 

 pores or cracks. 



As indicated in the figure, the shell is underlaid by the epi- 

 dermis, and this cellular layer supplies large glands from which 

 tubes perforate the inner part of the shell and then suddenly 

 becoming more narrow, continue on through the outer part to 

 the very surface as only 2.5 ^ wide. 



The laminated inner part of the exoskeleton is evidently the 

 secondary cuticula of Tower, ^ and the colored layer is his pri- 



' Development of colors and color patterns in Coleoptera. Chicago University 

 Pul)lications, 1903. 



