142 TWENTY-FOURTH REPORT ON THE STATE MUSEUM. 



away this portion, a flat surface is seen beneath, covered with a mat- 

 ting of intermingled hairs and silk ; if this matting be removed, a 

 moderate pressure of the fingers upon the sides of the cocoon, 

 will cause the flattened apex to detach itself in part from the body, 

 disclosing a perfectly fitting lid, of which its connection with the 

 cocoon for about one-third of its circumference, serves as a hinge. 

 The margin of the lid is slightly recurved ; that of the cocoon to a 

 greater degree, so as, in some examples, to render this portion as 

 broad as the central diameter. 



The lid is woven by the caterpillar separately from the rest of the 

 cocoon, and is not a section cut from it after its completion. This 

 interesting fact, at variance with the generally received opinion upon 

 the subject, was clearly shown, when, upon springing open the lid, 

 there was found to be resting upon and partly overlapping its margin, 

 and quite distinct from the matting inclosed, a packing of stout, 

 parallel threads and hairs, not forming an entire circle, but inter- 

 rupted by returns at each side of the hinge, over which its extension 

 would not be needed; underneath this, and more closely united to 

 the margin 1 was a more slender silken cord arranged in like manner. 

 The construction of the packing and its curious disposition, prior to 

 the formation of the lid, as from their relative position it must neces- 

 sarily be, is ample evidence that, in continuation of the plan adopted, 

 the lid is subsequently woven to its shape, with the packing serving 

 for its base and guide. 



The lids are usually of an ovate form, but in some specimens they 

 assume a subtriangular shape, or present one or more projecting 

 angles ; in such instances, these irregularities are met by comple- 

 mentary variations in *the margin of the cocoon, by which a 

 perfectly fitting lid is insured. 



A tranverse section of the cocoon displays an ingeniously con- 

 trived structure for the firm support of the margin of the lid, without 

 which, notwithstanding the partial support provided for it in the 

 inflated margin of the cocoon, it might too easily yield to outward 

 pressure from some inquisitive enemy. While as before stated, the 

 main body of the cocoon consists of a single w r all, its superior third 

 is seen to divide in several laminae (seven were counted in one 

 specimen), slightly separated and carried to the proper height to 

 meet and sustain the lid; the interior ones are thin, while that 

 forming the inner wall is firm and smoothly coated by a gummy 

 secretion probably from the inouth of the larva, uniform with 



