46 LEAF-MINING INSECTS 



I had shut up in a little box 2 chose the angles between the sides 

 and the bottom and cover of the box to spin cocoons. I went out 

 at once to examine the branches and stalks of the rose-bushes, in 

 the leaves of which I had noticed empty mines, in order to discover 

 the natural and unusual retreats of the insects. I found a good 

 many of them enclosed in cocoons which were ordinarily placed 

 in a chink or crevice of the bark of the stalks. Often they are 

 found in the angles with the branches made with one another or 

 in the angle formed by a large thorn with the branch to which it is 

 attached. The caterpillars chose such places because they find it 

 easier to fasten the threads of the cocoon all around their bodies 

 in such a place; a flat surface would not be so suitable. 



The cocoons in which they enclose themselves are oval and of 

 a white color; the white of some of them borders on yellow. 

 Although the walls are thin, they are closely fitting and very strong 

 and one can hardly tear them open without wounding the insect 

 within. In order to get the insect out of the cocoon without hurt- 

 ing it, it is necessary to use very fine scissors. I have often seen 

 the caterpillars begin and complete their cocoons, but their work 



has nothing peculiar about it As their bodies are supple 



they can bend and turn them in every way. It is easy to fasten 

 threads on all sides, to reinforce them and finally to make cocoons 

 of them. 



In the cocoons they very soon take on the form of chrysalids 

 of a fine yellow orange color, on which the parts of the future 

 adult are marked more distinctly than on ordinary chrysalids. 

 Their shape is oval. The abdomen which terminates in a trun- 

 cate cone is divided into segments. The sheaths which cover the 

 wings extend nearly to the end of the abdomen and have consider- 

 able width. The antennae and legs are arranged in the usual 

 order between the wings. 



It was not till June of the following year that I had occasion 

 to see what had become of my little miners. I found them changed 

 into winged insects; but what insects? — into Ichneumon flies. 

 They had pierced in the cocoons little circular holes which had 

 gained them their exit. This discovery struck me with astonish- 



* "Pou drier"— sand or dust box from which the sand was shaken to dry 

 ink as a blotter. 



