1911] Life-History of the Larch Case-Bearer 69 



silk. One larva must attack a great number of the small 

 young leaves, for in cases observed the larvae were not abundant 

 enough to do the damage they did unless each case-bearer 

 attacked and injured several leaves. As bearing on this 

 point I selected a branch 6 inches long and found that it bore 

 24 whorls of leaves, one whorl, at this particular stage, contain- 

 ing 54 small leaves and other nascent ones in the center that 

 could not be counted. If we take 54 leaves as the average, 

 the branch bore 1296 leaves that were of a size to be attractive 

 to the larvae. On this branch were 10 case-bearers. They 

 had injured every leaf on the branch except those in the last 

 whorl evidently having begun near the base of the branch and 

 worked outward. These ten larvae had probably attacked 

 and injured over a thousand leaves the majority of which, of 

 course, were small. 



On April, 26th I found the first pupa in the breeding cages. 

 When ready to pupate, the larvae attach their cases securely to 

 the branches or to the leaves often in clusters of 4 or 5. A 

 favorite place for attachment seems to be the center of a whorl 

 of leaves. The period of pupation, in the breeding cages at 

 least, proved to be from two to three weeks. We found moths 

 emerging in the insectary May 11, 13, 15, 16 and on. 



The moths begin pairing in a few days after emergence 

 and on May 31, their pinkish-red eggs were found deposited on 

 leaves in the 'breedings jars. The eggs are shaped as though 

 moulded in a tea-cup with many ridges radiating from the upper 

 and smaller end, for they are glued to the leaves by their 

 bases. 



On June 6th, in the field, an abundance of moths were found 

 and many of them were pairing. Some had probably emerged 

 a few days earlier. On June 10th I found eggs on the leaves in 

 abundance but there were still many pupae in cases showing 

 that the moths emerge over a Jong period. The eggs are 

 evidently placed indiscriminately on either side of the leaves. 



On June 28th and 29th the eggs were found hatching in the 

 field. The egg-shells remain glued to the leaf and show no 

 rupture of any kind for the emergence of the larva. Investi- 

 gation shows that the larva bores through the base of the egg- 

 shell and goes directly through the epidermis into the leaf 

 beneath the egg. Here the larvae live mining in the tissues of 

 the leaf but growing very slowly. The excrement of the tiny 



