BUTTERFLIES 107 



These were of a faded sky blue color, with a small black 

 spot in the center ; but as they had not been fertilized by 

 males, they did not hatch anything at all. 



In September, at Poggio Imperiale, I ordered a large 

 quantity of greenish yellow caterpillars to be gathered; 

 they were feeding on cabbage-stalks. I put them in 

 boxes, giving them the same food, i.e., cabbage. After 

 four days, they all climbed to the lids of the boxes, and 

 fixed themselves there motionless ; during this time some 

 had laid minute eggs, wrapped in yellow silk. After re- 

 maining quiet for three days, they shed, not all, but that 

 part of the skin which covers the head ; then slowly they 

 began to change shape and the skin commenced to 

 harden; they remained firmly attached to the boxes by 

 means of silken threads issuing from the tail and sup- 

 porting different parts of the body. In this guise they 

 remained all winter, but towards the month of March, 

 many became dry and ceased to move when touched, 

 others remained alive, with the power of partial motion 

 and these, abandoning their shells that still held to the 

 boxlids, escaped in the shape of pale, greenish-yellow 

 butterflies, having two round black spots on the upper 

 wings and two yellow horns on the head. Being led by 

 curiosity to open some of those chrysalides that had be- 

 come dry, and had ceased moving in March, I found that 

 the shell was empty, excepting in the part corresponding 

 to the chest, where I discovered a reddish pur- 

 ple Qgg, full of matter like milk or white of egg. On 

 May nth, from all these eggs there hatched flies of the 

 kind that ordinarily inhabit houses. These were at first 

 heavy, dull and misshapen, like those, described at the 

 beginning of this letter, and which originated from 

 worms bred in meats. In the meanwhile minute eggs, 



