ENTOMOLOGY 



twig; Tropcea tuna and Tclca polyphcmns spin among leaves, 

 and their cocoons (with some exceptions) fall to the ground; 

 Callosamia promethea, whose cocoon is covered with a curved 

 leaf, fastens the leaf to the twig with a wrapping of silk, so 

 that the leaf with its burden hangs to the twig throughout the 

 winter. The leaves surrounding cocoons - may render them 

 inconspicuous or may serve merely as a foundation for the 

 cocoon. While silk and often a water-proof gum or cement 



FIG. 215. 



Cocoon of Samia cecropia, cut open to show the two silken layers and the enclosed 



pupa. Natural size. 



form the basis of a cocoon, much foreign material, such as bits 

 of soil or wood, is often mixed in ; the cocoons of many com- 

 mon Arctiidse, as Diacrisia virginica and Isia Isabella, consist 

 principally of hairs, stripped from the body of the larva. 



Butterflies have discarded the cocoon, the last traces of 

 which occur in Hesperiidae, which draw together a few leaves 

 with a scanty supply of silk to make a flimsy substitute for a 

 cocoon. Papilionid and pierid pupae are supported by a silken 

 girdle (Fig. 27), and nymphalid chrysalides hang freely sus- 

 pended by the tail (Fig. 212). 



Cocoon-Spinning. The caterpillar of Telea polyphemus 

 " feels with its head in all directions, to discover any leaves 

 to which to attach the fibres that are to give form to the co- 

 coon. If it finds the place suitable, it begins to wind a layer 



