168 THE entomologist's record. 



NocTU^, &c. Many of the species that follow this course remain in 

 the egg for a very long period. Among the observations anent the 

 Geometr.*;, already referred to, will be found the following instances : 

 — Epione apiclaria, 9| months; Eugonia antmitnaria, 7| to .10 months; 

 Himera pennaria, 5 months ; Oporahia filigrammaria, 4| months ; 

 Cidaria testata, 8 months ; Chesias spartiatn, 4^ months. 



The condition of the egg during the hybernating period is much 

 more interesting. It is possible that some remain almost in the initial 

 condition as laid all the winter. Buckler records that eggs of Bombyx 

 mori, Trichiura crataegi, Engonia tiliaria, E. angnlaria {qnercinarui), 

 Cheimatohia hrumata, G. boreata, Scotosia vetulata, Vtilophora plnmlgera, 

 Xanthia aurngo and Pol/a 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, except in the case of A', aurago, the egg of which 

 on January 14th was found to contain a partially developed larva. 

 Some species, on the other hand, hybernate with the larva fully-formed 

 inside the egg-shell, and only waiting for the spring to eat its way out 

 and commence larval life. This appears to be a very similar condition 

 to that of many larvaj which hatch from the egg, bvjj: hybernate at once 

 without feeding ; only in the one case the larva? hybernate inside, in the 

 latter outside, the egg-shell: in both cases the larva is equally well- 

 formed. Thus in Parnassius apoUo the larva is fully formed in the egg 

 in autumn, but it does not hatch till early spring. 



12. — On the period over which the hatching process may extend. 

 — One of the most imjjortant facts in connection with the preservation 

 of a species, is, that in many species of more or less wandering habit, 

 the eggs do not all hatch at one time. I have frequently noticed that 

 of a batch of Orgyia antiqua eggs laid in August a few Avill hatch at 

 once and produce autumnal larvae, the remainder going over the winter ; 

 of these a few will hatch in May and after\vards at irregular j^eriods, 

 until when the last hatch they will have been in the egg state almost 

 twelve months. It is very clear that by this means many insects which 

 would, if the eggs all hatched simultaneously and under unsatisfactory 

 conditions, rapidly become extinct or suffer very considerably, are 

 much aided in their struggle for existence. 



13. — On the effects of exposing eggs to extreme tempera- 

 tures. — Mr. Merrifield, whose researches into the effects upon the 

 various stages of Lei^idoptera of varying degi'ees of temperature have 

 interested us so much of late years, has made some of his experiments 

 on the eggs of certain species. In The Transactions of ihe Entomological 

 Society of London, 1890, pp. 132-133, he reports that spring-laid eggs 

 of Selenia bilunaria began to have their vitality affected after being 

 " iced " (at a temi^erature of 33°) in the central red stage 28 days, and 

 none hatched after 60 days' icing. The case " Avas worse with spring- 

 laid eggs of S. tetralunarin, none of "udiich survived 42 days' icing, and 

 some summer-laid eggs of the same species fared no better. In all the 

 experiments up to 60 days' exposure, and I think beyond that period, 

 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. Tlic failure was a failure to hatch." 



Mr. Merrifield makes the folloAving remark (which, in the face of 

 the rest of the experiments, almost suggests an error of observation) : — 



