LEPIDOPTERA. 



151 



Fig. 109.— Caterpillar of the Pieris brassicse. 



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 gUde into the 

 bend or crease of its 

 neck by a httle move- 

 ment of its head. It 

 Tnust disengage its head 

 from under the band, not 

 a difficult operation. It 

 causes it to slide along 



the tifreads 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 chrysalides 

 (Fig. no), where the chrysalis of the above- 

 mentioned caterpillar is seen in two different posi- 

 tions, and held 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, 

 sometimes 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 interior of the cocoon, and which it 

 expels from the anus. Some cocoons are com- 

 posed of a double envelope, others are of a 

 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 chrysalis can be easily perceived 

 (Fig. III). 



Among caterpillars that make a very slight 

 cocoon, some, as the Catocalas, gather together 

 two or three leaves into a ball, to protect them. 

 Others strengthen their cocoons, and render them Pupae of pferis brassicse 

 opaque by adding earth or other substances, often 

 obtained from their own bodies. Some, after having spun their 

 cocoon, cast forth through the anus three or four masses of a matter 



