36 BEITISH LEPIDOPTERA. 



applied in the very early stages of the pupa, will generally mature 

 rapidly under the same treatment if applied some two or three months 

 afterwards. 



There must be, however, a great deal in the individual constitution, 

 for, of pupae from the same batch of ova, identically treated through- 

 out their whole existence, some will come out at the normal time 

 whilst others will last on as pupae for another year, and then, will only 

 emerge at the proper season for the insect to take on the imaginal 

 form, thus Baxter notes " fourteen Sphinx ligustri pupated in 1887, 

 eight emerged in June, 1888, and six in June, 1889 ; all fourteen were 

 subjected during the first year to the same conditions of heat, damp- 

 ness, &c." We ourselves note a long series oi Emmelesia albidata that 

 emerged in April, 1890, a large number of specimens having emerged in 

 April, 1889, from the same lot of pupa? received from Shetland in the 

 autumn of 1888. Bayne notes that, of a brood of Uucullia verbasci 

 that pupated in 1888, part emerged at the usual time in 1889, the 

 remainder on May 3rd, 1890. Miss Kimber records the pupation of 

 nineteen Notodonta trepida in 1888, in January, 1889, they were put in 

 a forcing-house (in one of the hottest parts of a hothouse), some came 

 out in May 1889, the other pupse went over, the heat in summer was 

 intense, hut in March and April, 1890, five fine imagines emerged. 



Even, in a state of nature, the influence of temperature on over- 

 wintering pupae is apparently very variable and uncertain. In 1893, we 

 had a remarkably hot and early spring and summer with the result 

 that Lepidoptera that hybernated normally in the egg stage had 

 hatched, and those that hybernated in the larval stage had 

 pupated, whilst imagines from both appeared, long before their usual 

 time, many getting in an abnormal second brood in August and 

 September. Of overwintering butterfly pupae the temperature appears 

 to have affected some, whilst others (of the same species) were quite 

 unaffected. Thus in early June, 1893, we note the possession of living 

 winter pupae of Pieris brassicae and P. rapae, and also pupae from eggs 

 laid in April ; at the same time we had overwintering pupae of Euchlo'e 

 cardamines, and eggs, larvae, and pupae of the year, &c. It is difficult to 

 find an explanation of this varying effect on different pupae of the same 

 species. 



There are species that are almost regularly double-brooded in this 

 country, and the fact that double-broods are more particularly notice- 

 able in hot summers, such as 1893, makes it certain that temperature 

 is an important factor in their development, but the fact ^hat partial 

 double broods are common almost every year, i.e., that from a single 

 batch of eggs laid in spring or early summer, a part of the larvae will 

 feed up rapidly and emerge in late summer or autumn, and produce 

 eggs, larvae, or pupae to over-winter in due course, whilst the re- 

 mainder linger on as over-wintering larvae or pupae (according to the 

 species) although treated exactly similarly, suggests that there is some 

 hereditary difference in the individuals themselves, as, indeed, has 

 already been shown in Arctia caia [ante, p. 16). Of species, the bulk 

 of which are single-brooded, but which produce a partial double-brood 

 on occasion, a very fair share of our lepidopterous fauna might be 

 enumerated — Papilla machaon, Peucophasia sinapis (always double- 

 brooded in south Europe), Brenthis euphrosyne, B. selene, Dryas paphia, 

 Nisoniades tages, &c, will at once occur to every lepidopterist. Clos- 



