232 THK CANADIAN ENTOMOLOGIST. 



FURTHER EXPERIMENTS UPON THE EFFECT OF COLD 

 APPLIED TO THE CHRYSALIDS OF BUTTERFLIES. 



h\ W. H. EDWARDS, COALBURGH, W. VA. 



In Can. Ent., vii., p. 236-240, I gave an account of experiments with 

 I'. AJax, placing the chrysahds on ice. In vol. ix., 4 and 203, of Ajax, 

 P. Tharos and L. Pscudarglolus. In Psyche, iii., 6 and 15, these were 

 all brought together, and additional observations on G. Interrogationis 

 were given ; also p. 174, on L. Disippus. In the case of the seasonally- 

 dimorphic AJax, the conclusion was reached, Psyche, iii., 18, that the 

 longer the exposure the more decided the change, but changes had been 

 produced at 1 1 to 30 days ; at and under 8 days no cliange was percep- 

 tible. That 30" to 40° Far. seemed to be the proper temperature for the 

 purpose. That the effect of the cold was to albinize the butterfly, the 

 black area being constantly reduced. 



That with G. Interrogationis, after the chrysalids had hardened, i. e., 

 about 1 2 hours after pupation, 14 days exposure, temp. 35° to 45°, had 

 been found sufficient to produce marked changes in coloration. That with 

 different species the degree of temperature required to produce the most 

 decided change varies ; the experiments best succeeding with P. Tharos 

 at 40°, Ajax 32" to 40^ At 32° had destroyed many Grapta Iiiterroga- 

 tio7iis chrysalids. The effect of the cold was to melanize the butterfly in 

 certain parts of the fore wings. 



In the case of P. Tharos a complete change of form was brought 

 about, the butterflies which naturally would have come out the summer 

 form, in every case coming out the winter form. Some chrysalids exposed 

 before they had hardened, at 30 to 60 minutes after pupation, were not 

 changed in form, but the colors had run, making what is called " suffused " 

 specimens ; but the butterflies from chrysalids which had been from i to 

 9 hours old, were completely changed. Tharos was the only species in 

 which it did not seem necessary that the cold should be applied only after 

 the chrysalis had hardened, in order to change the form. In other words, 

 this species was very susceptible to change either of form or color, and at 

 32" to 40°. 



This year, 1884, I have continued the experiments as follows, using 

 same treatment. 



I. Melit/EA Harrisii, Scud. In all cases the tin boxes containing 

 the chrysalids were laid on the surface of the ice in ice-house, where the 



