temperature on the colouring of Lepidoptera. 39 



light band, to grow darker as the length of the period of 

 pupation, and consequently of exposure to the low 

 temperature, increases. 



Var. callume. " Family A:'—k few sent from Aber- 

 deen were placed at 80°, and two emerged in from 27 to 

 46 days. I exhibit these, which are a good deal lighter 

 than usual, especially the female, which can scarcely, if 

 at all, be distinguished from the southern form. Another 

 familij, " J5," from Perth, similarly forced, produced 

 three males and two females. These are darker, but 

 light for calhnue. I produce a fair sample of each sex; 

 the males exhibited are perhaps slightly lighter than the 

 average of the three. Another, >?»?,/?/ " C," from Perth, 

 was divided ; five males and five females were forced at 

 80°, appearing in from 29 to 42 days, and I exhibit two 

 pairs of these — fair samples — one of the males slightly 

 lighter than the average of the five. Six males and nine 

 females were placed in the open air, and emerged in June 

 and early in July ; these varied but little. I produce 

 two pairs which emerged between 28th June and 1st 

 July, fair samples of the 11, except that one male is 

 slightly darker than the average of the six males. It 

 will be seen that the males especially are darker than 

 those which had been forced. 



To sum up as to quercus and callwKe. The same 

 general result which has been noticed in other cases 

 obtains here ; that is, those at the higher temperature 

 are lighter than those at the lower temperature. This 

 particularly applies to the males, the females varying 

 less; but in both males and females the forced ones 

 have a reddish tint, which is wanting in the others. In 

 some cases the effect of temperature is so considerable 

 that I think some of the forced callunce would, so far 

 as regards colouring, be classed as quercus, while the 

 individual quercus brought out in 71 days at the lower 

 temperature is very dark for quercus. 



I think these experiments tend to show that the 

 southern form and its northern var. are respectively 

 varieties of so fixed a kind when they reach the pupal 

 stage that it is probably only in exceptional instances, if 

 at all, that temperature could convert the one form, so 

 far as its appearance is concerned, into the other. But 

 further experiments should be made, especially in the 

 application of a low temperature to the southern form 



