152 ENTOMOLOGY 



Emergence of Pupa. Subterranean' pupae wriggle their way to 

 the surface of the ground, often by the aid of spines (Fig. 219), 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. These structures are found also in pupae, 

 as those of Sesiidae, that force their way out of the 

 stems of plants in which the larvae have lived. The 

 emergence from the cocoon is accomplished in some 

 cases by the pupa, in others by the imago. Hemero- 

 biidae, Trichoptera and the primitive lepidopteron 

 FIG. 219. Sub- Eriocephala use the pupal mandibles to cut an open- 



terranean pupa of f ^ * 



Anisota. Enlarged, ing in the cocoon; while many lepidopterous pupae 

 have on the head a beak for piercing the cocoon, or 

 teeth for rending or cutting the silk. 



Eclosion. During the last few hours before the emergence of a 

 butterfly the colors of the imago develop and may be seen through the 

 transparent skin of the chrysalis (PL II A) . No movement occurs, how- 

 ever, until several seconds before emergence; then, after a few convul- 

 sive movements of the legs and thorax of the imprisoned insect, the 

 pupa skin breaks in the region of the tongue and legs (B), a secondary 

 split often occurs at the back of the thorax; and the butterfly emerges 

 (C-E) with moist body, elongated abdomen and miniature wings. 

 Hanging to the empty pupa case (F), or to some other available sup- 

 port, the insect dries and its wings gradually expand (G, H) through the 

 pressure of the blood. At regular intervals the abdomen contracts 

 and the wings fan the air, and sooner or later a drop or two of a dull 

 greenish fluid (the meconium) is emitted from the alimentary canal. 

 The expansion of the wings takes place rapidly, and in less than an 

 hour, as a rule, they have attained their full size (7) . 



T. polyphemus is "provided with two glands opening into the mouth, 

 which secrete during the last few days of the pupa state, a fluid which is 

 a dissolvent for the gum so firmly uniting the fibres of the cocoon. This 

 liquid is composed in great part of bombycic acid. When the insect has 

 accomplished the work of transformation which is going on under the 

 pupa skin, it manifests a great activity, and soon the chrysalis covering 

 bursts open longitudinally upon the thorax; the head and legs are soon 



