141 BIOGRAPHY OF HEMILEUCA MAT A. 9 



Dr. Speyer, and in this country by Mr. Riley. They have been found 

 by Mr. Riley, in clusters, beneath the bark of the trees upon which the 

 larvae feed, appressed closely together and partly overlapping, with no 

 protection beyond that afforded by the shelter of the bark. 



But that these coverings are not indispensable to a safe hybernation 

 is shown by the entirely naked and exposed egg-belts of H. Maia y 

 and of the Lackey Moth (Clisiocampa neustria) of Europe. The eggs 

 of the former moth, from which emerged the larvae which form the 

 subject of this paper, endured a winter in which the thermometer in 

 their immediate vicinity fell to 8 below zero of Fahrenheit.* 



Some experiments which have been made to ascertain the effects of 

 cold upon the eggs of insects have disclosed the fact that they possess 

 a remarkable power of retaining their vitality under very low tempera- 

 tures. The eggs of a Yanessa and of several other Lepidoptera, were 

 exposed by Spallanzani for five hours to a freezing mixture indicating 

 22, without the least injury resulting to them, for they all subse- 

 quently disclosed their larvae. 



It is probable that the eggs are in reality not frozen, but that their 

 contents continue fluid under the greatest cold to which they may be 

 subjected in their natural exposure. Some eggs of 0. leucostigma 

 before referred to, which I had divested of their covering and left 

 exposed during a portion of the winter, were examined by me under a 

 temperature of 18 below zero, and were found to be in their natural 

 fluid condition. 



For this extraordinary capability of resisting cold, no satisfactory 

 reason has been assigned. Among other conjectures, it has been sug- 

 gested that a spirituous or an oleaginous element might possibly enter 

 into the composition of the eggs. 



Hatching. The larvae emerged on the 27th of May, sixteen days 

 after they had been brought within doors, and deposited in a glass- 

 covered box. Their escape from the shell was, without a single excep- 

 tion, from the apex, through a regular elliptical opening eaten by the 

 larvae, corresponding in outline to a depression previously existing. A 

 very few of the eggs did not develop.f 



Egg-shell. The shells are translucent, of a brownish-yellow color 

 superiorly, and whitish on their basal half. J^o portion of the shells, 

 beyond that above mentioned, was eaten by the larvae. 



* The eggs of our November Motli (OporaUa dilutata Albin) pronounced by 

 Fitch identical with the European species are doubtless deposited in the month 

 of November, nakedly, upon the twigs or buds, as are those of its European allies. 



f In the belts subsequently collected, there were found quite a number of unde- 

 veloped ova. In one belt, but one of the eggs composing the first ring had produced 

 its inclosed larvae. 





