REPOET OF THE ENTOMOLOGIST. 211 



the mine of tlie latter is only observable from tbe upper side of tlie leaf, 

 wbiie tbat of oar insect can be seen from both sides and is also of a 

 darker color. 



The mine when completed is an irregular, frequently more or less 

 triangular, ratber dark colored blotob, averaging 6 or 7""" in its longest 

 diameter and observable from both surfaces of the leaf. Up to the tune 

 when the larva has attained full growth the mine is translucent, the 

 only dark spots being the larva itself and the excrement which is col- 

 lected in an irregular cake of minute pellets in the region where the 

 mine was first begun. Soon^ however, the translueency of the broader 

 end of tlie mine begins to be obscured in an oval spot, and if it could be 

 opened the larva would be found busily engaged in lining both surfaces 

 of the leaf with white silk, mapping out the size and shape of its future 

 case. After this lining has become sufficiently thick, the larva com- 

 mences to cut through, both surfaces of the leaf at the edge of the oval 

 lining, and to draw them together and fasten them with silk as it goes. 

 When the circumference of the oval has been cut and fastened, witli the 

 exception of a small portion at one end, the larva at that point cuts 

 through the ujyper surface alone, partly issues from its case, and weaves 

 a strong cord of silk from the surface of the leaf on beyond the mine 

 back to the mouth of the case. Then, everything being securely fast- 

 ened, it cuts the last band of the lovrer membrane which still remains 

 intact, and stauds upon the upper surface of tlie leaf with its completed 

 case upon its back. The next step is to cut the supporting cord, and 

 the larva is free to start upon its travels. 



In walking, the head and first tbree thoracic segments alone are pro- 

 truded from the case, the soft hinder parts being thus protected. The 

 abdomen with the inclosing case is lifted erect in the air, so that it does 

 not drag upon the insect as it walks. After progressing for an inch or 

 so the larva usually drops from, the leaf, spinning a long silken thread 

 as it falls. In this way it either reaches the ground, or, what is much 

 more common, falls upon or is blown by the wind to a limb or the trunk. 

 It travels a greater or less distance further until it finds what seems to 

 it to be a proper i)lace, and there, after attaching the case firmly to the 

 bark by a button of silk, it sooner or later transforms to a pupa. 



Ko food is taken after the case is begun. The posterior end of the 

 case is left slightly open, although there is no necessity for an anal open- 

 ing through which to pass the excrement, as in Coleophora; neither is 

 any excrement to be found in the case, all having been left behind in 

 the mine. After fastening its case permanently, but before transforming 

 to the inipa state, the larva reverses its position in the case, so that its 

 head is towards what was formerly the posterior end. 



When the time arrives for the moth to make its exit, the pupa works 

 its way out through the posterior slit in the case until it is half emerged, 

 and in that position gives forth the moth. 



Dr. Packard* speaks of the forming of the cases in the latter part ot 

 August and September. Mr. Chambers t also states this to be the cus- 

 tomary time, and August was the month in which Dr. Clemens t found 

 them. In Washington, however (and this would probably hold true in 

 the field of Mr. Chambers's observations), there are two broods in the 

 course of tlie season. During the past summer the first cases were ob- 

 served on July 16, and July 23 the first moth issued, and from this date 

 tiU the middle of August they were continually issuing. This first brood 



* Guide to the Study of Insects, p. 355, 

 t Canadian Entomologist, vol. iii, p. 223. 

 t Proc. Acud. Nat. Sci. Phil., 18G0, p. 13. 



