334 



BRITISH BUTTERFLIES. 



f. Number unstated. Kept at 33°F. for ten weeks, then at 55°F. for five weeks 

 (winter and spring temperatures) (figs. 2 and 2a). About half died or were crippled. 

 In those which emerged all the effects of the low temperature are shown in their 

 extreme — light colour of coppery parts, reduced size of spots (one or two of which 

 have almost disappeared) ; the breadth and conspicuousness of the coppery band on 

 hindwings, which ceases to be serrated, though coppery scales are often prolonged 

 along nervures, from band towards base of wings. 



7]. Six pupae. Exposed at 33°F. for nine or ten weeks, then at 90°F. ; all 

 emerged in from 5-6 days. These have most of the features of lot a, which were 

 never at a lower temperature than 80°F.-90°F., and especially the dusky suffusion 

 of bases of forewings, and reduced size of coppery band on hindwings. The 

 contrast in colouring between these and the last lot, f , is noticeable. 



Merrifield observes that the principal effects on -colour appear to be 

 produced, not by long exposure to severe cold, but by exposure, during 

 the period when the active part of the pupal changes has begun, to 

 (1) great heat, producing duskiness ; (2) moderate cold, producing 

 vividness and intensity of colouring in both the coppery and the dark 

 parts, smallness of spots, and great enlargement of the copper band 

 on the hindwings. Merrifield further remarks the interesting 

 parallelism apparently produced naturally by temperature in the 

 American insect — B. hypophlaeas, of which, Scudder remarks that 

 the spring individuals (i.e., those which emerge in colder weather) 

 are of a more fiery red, and the orange band on the undersurface of 

 the hindwings is broader ; while, in later broods, viz., those emerging 

 in the hot American summer, the markings are less vivid and less 

 distinctly defined. He adds that there is also a longer tooth 

 on the margin of the hindwings, a feature that appears to exist 

 in a slight degree in the p.hlaeas reared by Merrifield at a high 

 temperature, the orange band on the undersurface of the hindwings 

 being, in all these examples, very inconspicuous. Frohawk, however, 

 notes that the markings on the undersides of all the wings are consider- 

 ably stronger in those exposed to high, than in those developed 

 at lower, temperatures, and in those at the lowest temperature the 

 spots on the forewings are much reduced in size, and on the hindwings 

 are almost obliterated. Weismann's comparison of these experi- 

 ments (Ent., xxix., p. 38) is interesting, and there is no doubt 

 that the difference observed in the appearance of the specimens 

 is merely due to a modification of the chemical processes in 

 the development of the colour-material in the scale in which a high 

 temperature produces darkening, and moderate cold a brightening of 

 the colour. It is clear, however, that the changes that may be 

 produced artificially are limited by the racial variation exhibited in 

 this species in the widely different latitudes that it inhabits, and 

 that the races of warm climates react more readily to higher, and 

 less readily to low, temperatures, whilst those from cold climates 

 react more readily to low, and less readily to high, temperatures. 

 Weismann gives (Ent., xxix., pp. 74 et seq.), too, considerable details of 

 the variation in the markings of }>hlaea.s, independent of climate. He 

 notes, with regard to the development of blue spots on the outer margin 

 of the upperside of the hindwings in both sexes, that as many as four 

 may be present, but often one or other of the spots is only indicated by 

 scattered blue scales, frequently only by a single one, and not infre- 

 quently no trace of the spots is to be seen at all. If specimens from 

 the south be compared with those from the north, it is seen that well- 

 developed spots and their indications are much more frequent, but 



