THE OVUM OR EGG. 15 



April ; of the Catocalids, from July and August to April, and so on. 

 The condition of the egg during the hybernating period is very 

 interesting. In some species, such as Aryynnis adippe, Pampldla 

 comma, Parnasxiux apolln, etc., the fully formed caterpillar remains 

 coiled up within the shell all the winter ; in others, the eggs appear to 

 remain until spring, almost in the same condition, so far as the con- 

 tents are concerned, as that in which they were laid. Buckler records 

 that eggs of Sombyx mori, Trichiura crataeiji, Ennotnos (alniaria) tiliaria, 

 E. quercinaria, Cheimatobia brumata, C. boreata, Scotosia vetulata, 

 Ptilopkora plumiyera and Polio, chi, have been examined from time to 

 time until the middle of January, and nothing but the faintest traces 

 of the future larvae have been detected by a microscopic examination of 

 their still fluid contents. In the case of Tiliacea (Xanthia) aurai/o, 

 however, an egg was found to contain a partially developed larva on 

 January 14th. It occasionally happens, as in the case of Polio, 

 .rantJioiiiista var. nii/rocincta, that part of a batch of eggs, which 

 should normally hybernate during the winter, hatches in the autumn, 

 and the larvae attempt to feed up, whilst the remainder of the 

 batch goes over normally. It is recorded, also, that in a batch 

 of Oryyia antiqua eggs, the hatching takes place most irregularly, a 

 few larvae appearing at a time, and the emergence of the whole brood 

 thus spread over a long period. This happens also in Epione apiciaria, 

 Laiiocampa tnfolii, Catocalia species, etc. 



The influence that temperature has on the hatching period, and on 

 the vitality of lepidopterous eggs, has been well shown by Merriiield. 

 lie has recorded that eggs of Selenia bilnnaria, and those of Selenia 

 tetralwiaria, were quite uninjured by exposure to a temperature of 

 from 80 F. to 90 F., their development, on the contrary, being 

 greatly accelerated. Spring-laid eggs of 8. bilunaria began to have 

 their vitality affected after being " iced " (at a temperature of 32 F., 

 when they were in the central red stage), for 28 days, and none 

 hatched after 60 days' icing. The result was even worse with spring- 

 laid eggs of 8 den i a tetralwiaria, none of which survived 42 days' 

 icing, and some summer-laid eggs of the same species, exposed to the 

 same conditions, fared no better. In all the experiments, up to 60 

 days' exposure, nearly all the eggs, after being removed from the ice, 

 matured so far as to admit of the formation of the young larva, which 

 could be seen through the transparent shell. The failure was a failure 

 to hatch. 



Standfuss has recorded that eggs of Arctia fasciata, Dasychim 

 alictix, Odoneatis (Lasiocampa) pruni and Dendrolinnia pini, which were 

 exposed to a temperature of 30 C. (93 F.), during the process of 

 laying by the female, and up to the time of hatching, produced larvae 

 in two-thirds or less of the normal time, and there emerged as perfect 

 insects in the same year, i.e., without hibernation of the larva, in the 

 case of A. fam-iata, 71 per cent.; of D. abietis, 90 per cent. ; of (.). 

 jn-uni, 100 per cent. ; and of D.pini, 81 percent. The larvae and pupae 

 of the broods were kept, as far as possible, at a mean temperature of 

 25 C. The eggs of the same females as those used in the above experi- 

 ment, which had already been laid at a normal temperature (22 C.), 

 and were left in this until hatched, afterwards remaining in the same 

 mean temperature of 25 C., as the other larvae and pupae, produced a 

 considerably smaller number of perfect insects, without hibernation of 



