I06 GENERATION OF INSECTS 



sembling those silkworms that sicken and almost spoil 

 before they make the cocoon and are vulgarly called 

 "cows." In this state they remained vmtil the night of 

 the fourth of August, when six of these caterpillars, 

 having shed their skin for the third time, changed into 

 chrysalides of a blackish color, resembling so many 

 babies in swaddling clothes. I had occasion on the fol- 

 lowing morning to see the way in which these caterpillars 

 transformed themselves; the external skin opens at the 

 back near the head, separating from it and cleaving into 

 two parts, and from the cleft the chrysalis begins 

 to come out, writhing constantly, twisting, and contorting 

 itself, until it has pushed all the skin down to the end 

 of its tail; in the meanwhile the head grows noticeably 

 larger, and the tail becomes thinner, so much so that 

 when the process of transformation is completed, the 

 chrysalis has taken on the shape of a cone, is soft to the 

 touch and of a green color. But the green color, be- 

 ginning from the end of the tail, changes over the whole 

 body, little by little, and with this change of color the 

 skin hardens; the neck is the last part to change, but 

 wdien it has turned red, then all the rest of the chrysalis 

 has become black and has entirely hardened. This process 

 is begun and ended in scarcely more than half an hour, as 

 I have had ample opportunity to observe on many occa- 

 sions. When all the caterpillars w^ere changed into chrys- 

 alides, which was on August sixth, they retained 

 this shape until the following Spring, and then near the 

 end of April, the butterflies were born : they were all of 

 the same kind, but did not appear at the same time, as the 

 caterpillars had taken on the chrysalis stage at different 

 times. Many of these butterflies, soon after birth, laid 

 their eggs to the number of thirty or forty at most. 



