Dl \ I I M| 





pupa- are supported by a silken girdle i ad n\ mphalid < h 



lidcs haim freely suspended by t In- tail i 



Cocoon-Spinning. The i aterpillar of Tdea polyphemu vith 



its head iii all direction^, l> di my leaves 1<> whi< li ' '> the 



lil>re> that arc to uivr form to the cocoon. If it finds t he pla< -nit able, 

 it begins to wind a layer of silk around a t witf, then a fibre i> a Mai lu-d to 

 a leaf near by. and by many times doubling this fibre and making it 

 shorter every time, the leaf i> made to approa< h the twi^ at the di-' 



-ary to Imild the cocoon; two or three Leaves are disposed lik( thi- 

 oiu- and llu'ii the tihres are spread between them in all directions, and 

 >oon the ovoid form of the cocoon distinctly appears. This seems to 



Fu;. 218. Cocoon of Satnia cecropia, cut open to show the two silken layers and the 

 enclosed pupa. Natural size. 



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 

 zigzag lines 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 distrib- 

 ute- 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 distinguished through the fine texture of the wall; then 

 a mimmy 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 few minutes of rest, and finally another 

 coating is spun in the interior, when the cocoon is all finished and com- 

 pletely air tight. The fibre diminishes in thickness as the completion 

 of the cocoon advances, so that the last internal coating is not half so 

 thick and so strong as the outside ones." (Trouvelot.) 



