DEVELOPMENT I/ 1 



of silk around a twig, then a fibre is attached to a leaf near 

 by, and by many times doubling this fibre and making it 

 shorter every time, the leaf is made to approach the twig at 

 the distance necessary to build the cocoon ; two or three leaves 

 are disposed like this one, and then fibres are spread between 

 them in all directions, and soon the ovoid form of the cocoon 

 distinctly appears. This seems to be the most difficult feat 

 for the worm to accomplish, as after this the work is simply 

 mechanical, the cocoon being made of regular layers of silk 

 united by a gummy substance. The silk is distributed in zig- 

 zag lines of about one-eighth of an inch long. When the 

 cocoon is made, the worm will have moved his head to and 

 fro, in order to distribute the silk, about two hundred and 

 fifty-four thousand times. After about half a day's work, the 

 cocoon is so far completed that the worm can hardly be dis- 

 tinguished through the fine texture of the wall ; then a gummy 

 resinous substance, sometimes of a light brown color, is spread 

 over all the inside of the cocoon. The larva continues to work 



for four or five days, hardly taking a 



. FIG. 216. 



few minutes of rest, and finally another 



coating is spun in the interior, when 

 the cocoon is all finished and completely 

 air tight. The fibre diminishes in thick- 

 ness as the completion of the cocoon 

 advances, so that the last internal coat- 

 ing is not half so thick and so strong 

 as the outside ones." (Trouvelot.) 

 Emergence of Pupa. Subterranean 



wriggle their way to the surface Subterranean P u P a of 



f. . , r i ,i 1 r Anisota. Enlarged. 



ot the ground, often by the aid of spines 

 (Fig. 216) that catch successively into the surrounding soil. 

 These locomotor spines may occur on almost any part of the 

 pupa, but occur commonly on the abdominal segments, as in 

 lepidopterous pupae ; the extremity of the abdomen, also, bears 

 frequently one or more spinous projections, as in Tipulidae, 

 Carabidae and Lepidoptera, to assist the escape of the pupa. 



