THE SWALLOWTAILS 61 



enemies, although they seem not to be effective against in- 

 sect parasites. 



The full-grown caterpillars are likely to leave their food 

 plants when ready to change to the chrysalis state. They 

 wander in various directions imtil suitable shelter is found. 

 A piece of board, a fence post, or possibly the bark of a 

 tree will answer for this purpose. Here the caterpillar 

 spins a mat of silk in which to entangle its hind legs and a 

 short distance away near the front end of the body it 

 spins a loop of silk attaching the ends to the support. 

 These serve to hold the chrysalis in place during this help- 

 less period. After the loop is made the caterpillar keeps 

 its head through it so that the loop holds the insect in po- 

 sition a short distance back of the head. It is now ready 

 to moult its last caterpillar skin and become a chrysalis. 



One who has watched hundreds of these caterpillars go 

 through this change, ISIiss Mary C. Dickerson, describes 

 the process in these words: "In tliis final moult the chrys- 

 alis has to work very hard. The bulk of the body is 

 again slipped forv^ard in the loosened caterpillar skin, so 

 that this becomes tensely stretched over the anterior end, 

 and very much wrinkled at the posterior end. The skin 

 splits back of the head and is forced back by its own taut 

 condition and by the efforts of the chrysalis, until only the 

 extreme posterior end of the chrysalis is within it. Then 

 the chrysalis withdraws this posterior end with its many 

 very tiny hooks, from the skin on the dorsal side, and, 

 reaching around, securely fastens the hooks into the button 

 of silk. Then the old skin is removed both from its fasten- 

 ing to the chrysalis and from its attachment in the button 

 of silk." 



A short time after the caterpillar's skin has thus been 



