LEPIDOPTEEA. 



155 



Fig. 109. Caterpillar of the Pieris brassieae. 



gently over the last quarter of the circle. At last the caterpillar 

 finds itself bound on the second side ; the head rests on the 

 thread-covered plane, and the insect fixes the second end of the 

 thread." 



It has only to repeat the same manoeuvre as many times as 

 there are threads wanted to make a strong band. But each 

 thread embraces the head, 

 or rather the lower part 

 of the head, for it knows 

 how to make each thread 

 it spins glide into the 

 bend or crease of its 

 neck by a little movement of its head. It must disengage this 

 head from under the band, not a difficult opera- 

 tion. It causes it to slide along the threads near 

 one of the places where they are fixed, and it is 

 then in the position indicated by the foregoing 

 engraving (Fig. 109). 



About thirty hours after the caterpillars have 

 succeeded in making themselves fast, they have 

 completed their transformation into pupse (Fig. 

 110). In that the pupa of the above-men- 

 tioned caterpillar is seen in two different posi- 

 tions, and kept down by the same band which first 

 supported the caterpillar. 



Those caterpillars which construct cocoons, make 

 them of silk and other substances. These cocoons 

 are, for the most part, oval or elliptical, some- 

 times boat- shaped, and ordinarily white, yellow, or 

 brown in colour. The threads may very slightly 

 adhere together, or be closely united by a gummy 

 substance with which the caterpillar lines the in- 

 terior of the cocoon, and which it expels from the 

 anus. Some cocoons are composed of a double envelope, others are 

 of an uniform texture. Some are of a tissue so close that they 

 entirely hide the chrysalis contained within ; others form a very 

 light covering, through which the chrvsalis can be easily perceived 

 (Fig. HI). 



Fie. 110. Pupae of 

 Pieris brassicie. 



