EEPOET OF THE ENTOMOLOGIST. 229 



tained raoth begin to be plainly visible, and it seems to be completely 

 differentiated a day or two before it makes its exit. 



Eight days after the tirst pnpae were found the moths began to make 

 their appearance. Each pupa first sawed through tlie cocoon near its 

 juncture with the leaf and worked its way tlirough the gap, by means 

 of the minute backward-directed spines upon its back, until it reached 

 the upper cuticle of the leaf. Through this cuticle it sawed in the same 

 way that it did through the cocoon. The hole was in each case just 

 large enough to i^ermit the chrysalis to work its way out, holding it 

 firmly when partly emerged. When half way out it stopped, and pres- 

 ently the skin split across the back of the neck and down in front along 

 the anteunal sheaths, and allowed the moth to emerge. 



The moth is a delicate little creature, with a body about 3""" (.12 inch) 

 long, and with a stretch of wing of about 7""" (.28 inch). The front 

 wings are white, with three broad irregular bronze bands across each 

 one, each band being bordered with black on its inner side. The hind 

 wings are silvery. 



From the time when these insects were first observed until the end of 

 the season the moths were constantly issuing, there being almost no 

 regularity in the generations, so that from this season's observations it 

 would not be easy to state definitely the number of broods. The cycle 

 of. the insect's life occupying, as it does, but asingle month, more or 

 less, in this latitude, with seasons varying in length and degree of 

 warmth, the number of broods will vary by one or two. Five or six is 

 probably a close approximation. 



Upon the approach of cold weather, all the larvae which have entered 

 upon the last larval stage, the round form, undergo no further transfor- 

 mations at that time, but remain in this stage through the winter. The 

 larvae which have not yet reached this stage continue their develop- 

 ment up to this point, unless frost and the fall of the leaves cut them 

 ofi", and also hibernate as round larvae. This arrest of development, if 

 it may be so termed, of the larva before its last molt, took place this 

 year (and it is probably usually the same) with the advanced larvae 

 several weeks before cold weather set in, at just that point when the 

 development of another generation would have been impossible, thus 

 securing the hibernation of a;lmost every individual. * An examination 

 of the leaves in December revealed the fact that dead partially grown 

 larvae were very rare indeed in the mines. All through the winter the 

 dead leaves on and under the oaks most infested daring the summer 

 were full of the round larvae. Kot a single pupa was found, though 

 hundreds of mines were opened and examined. Such pnpae as there 

 may be upon the fall of the leaves (though they are probably very few, 

 if indeed there are any at all, from the reasons just stated) either give 

 forth the moths or are killed by the frost. The moths may possibly 

 hibernate in small numbers, though we have no evidence of such hiber- 

 nation.* 



Early in Jrarch the hibernating larvae revived after a few days of 

 warm weather and began spinning their cocoons. During the winter 



*Mr. Chambers saya (ibid., }>. 148): "Neither can I conceive any good reason why 

 moths disclosed late in the fall might not winter, and indeed the moths of L. robinieUa 

 and L. aalicifoUeUa do ; hut I have never met with any others hibernating, and indeed 

 I have not seen L. salicifoUella later than November. There are, however, some facts 

 about the hibernation of the species which need further explanation. Thus, I have 

 known L. tubiftrella Clem. andX. aescnlisella Cham, to pass into their last larval state 

 in the middle of August and to remain in that condition imtil late in the fall, when 

 my last observations were made upon them, and in such cases there was abundant 

 warmth and time for another brood before the fall of the leaves." 



