44 BULLETIN 322 



In the spring of 1910 the larvae had begun migrating to the buds by April 

 15, but in 1911 they were about ten days later owing to the retarded 

 opening of the buds. Before leaving its place on the branch the larva 

 sheds its skin. The cast skins, with the dark-colored skeletons of the 

 head, can be found among the tangled silk on the twigs where the case- 

 bearers were fastened during the winter. 



The young larva attacks a leaf in an interesting manner. It eats a 

 tiny hole through the epidermis of the leaf and mines out the inside tissues 

 of the leaf as far on each side of the entrance opening as it can reach. 

 During this time it does not let go its hold of the case, but remains attached 

 to it by its posterior prolegs and wriggles back into it when disturbed. 

 Attacked leaves soon assume a bleached, whitened appearance (Fig. 10), 

 and when deserted by the larva they shrivel and curl. 



One larva must attack a great number of the small young leaves, for 

 in cases observed in 1910 the larva? were not abundant enough to do the 

 damage that they did unless each case-bearer attacked and injured several 

 leaves. As bearing on this point, a branch six inches long was selected 

 and it was found that this branch bore 24 whorls of leaves; one whorl, 

 at this particular stage, containing 54 small leaves and other nascent ones 

 in the center that could not be counted. If 54 leaves be taken as the 

 average, then the branch bore 1,296 leaves that were of a size to be attrac- 

 tive to the larvae. On this branch were ten case-bearers. These larvae 

 had evidently begun at the bottom of the branch, for they were now near 

 the tip, and every leaf of any size had been injured except those in the last 

 whorl. Moreover, the larvae had injured the outside leaves first because 

 these were largest, and now they were going down into the middle of the 

 buds to get at the small growing green leaves in the center. These ten 

 larvae had probably eaten and injured over a thousand leaves. 



About the first thing that a case-bearer does after it reaches the fresh 

 buds in the spring is to enlarge its old winter case. This it does by slitting 

 the case lengthwise on the underside and then inserting a gore of silk. 

 The buds are not far enough out at this time so that the larva can obtain 

 leaves for enlarging its case. In the spring of 1912 the case-bearers first 

 began migrating to the buds on April 2 1 , a warm, sunny day. They lived 

 on the growing buds for nearly ten days before they were able to find 

 leaves long enough to cut off and fasten to their cases over the slit already 

 made and filled with silk. In addition to this enlargement in diameter 

 of the case, it is also now increased in length by the addition of silk to the 

 anterior end. The new leaf is usually cut longer than the old case, so 

 that on the underside of the case the leaf extends the whole length 

 (Fig. 9). At this period in the life of the larva it destroys many leaves, 

 for it passes from one to another as has been already pointed out. Cecconi 



