VARIATION AND ABEKRATION IN BUTTERFLIES. 145 



other i^laces also this darkening occurs at the edge of the silver 

 spots ; otherwise these show no substantial deviation from normal 

 specimens. 



10. Dasychiya ahietis, Schiff. 

 a. Warmth. 

 Sixty hours at 37° C. (98°— 99° F.) killed 18 pupa? of this 

 species so quickly that not one of them showed anything even 

 approaching a perfect insect. 



b. Cold. 



Forty-two days refrigerator, then 12 — 15 days at the normal 

 temperature, 6 male and 6 female pupae gave 1 male and 4 

 females, all perfectly developed. In the remaining 7 pupas the 

 imago was fully formed, but did not emerge. 



The blackish-brown scales besprinkled over the light ground 

 colour are increased in amount. Moreover, the few scattered 

 shades towards the anal angle of the hind wing are darker and 

 more sharply defined. 



From the facts now adduced it should be sufficiently clear 

 that the influence of temperature in the pupal stage operates 

 upon the aspect of the resulting perfect insect in an eminently 

 delinite manner. This, it is true, is clearly recognisable only in 

 respect of the colouring and marking of the wings, but it is at 

 times certainly visible in the shape as well. 



In the first place we witness in part, by the experiments here 

 communicated, the production of "seasonal forms" (as in the 

 case of V. c-album, and to some extent in that of P. machaon) ; 

 forms, that is, with a similar aspect to those that occur among 

 the palsearctic fauna at certain definite seasons of the year.* 



Secondly, there arise in part local forms and races ; forms, 

 that is, that occur constantly in certain definite localities, as in 

 the case of V. urticce, V. cardid, and to some extent P. machaon 

 and V. antiopa. 



In both of these results we have to deal with forms which, 

 under the received nomenclature of the present day, come within 

 the definition of "varieties," inasmuch as they constitute devia- 

 tions from the types of the species which have become constant, 

 and which keep to definite times of year (seasonal forms) or 

 localities (local races). 



Thirdly, there seem to arise forms of an entirely similar 

 aspect to some which also occur exceptionally here and there at 

 the present stage of the earth's history — that is to say, " aber- 

 rations." 



■•'■ It should here be mentioned that autumnal pupae ought also to be sub- 

 mitted to these experiments, as was done by Weismanu in the methodical 

 conduct of his investigations. The experiments discvissed above weie only 

 undertaken with siimmer pupae. 



