temperature on the colouring of Lepidoptera. QS 



Moreover, when a considerable number of individuals, 

 say, 10 to 20, were brought out at the moderately low 

 temperature, the colouring as a whole, but not regularly, 

 gradually darkens in proportion to the length of the 

 exposure. I do not ascribe this directly to retardation, 

 but to the fact that the physiological changes go on very 

 slowly at the lower temperature ; so that several weeks are 

 necessary to produce as great an effect as several days at 

 a forcing temperature would be sufficient for. A striking 

 illustration of the delicacy with which the colouring 

 responds when the temperature is applied precisely at 

 the right time is afforded by the following circumstance. 

 I had about a dozen of the summer emergence, which 

 had been brought out at 80°, and, on looking them over 

 after they were set, I noticed that three were decidedly 

 deeper in colour than the rest. This perplexed me, until 

 I remembered — and I found, on referring to my record, 

 that I was right — that these three had been placed in 

 the forcing-box at a separate time, and must have been 

 more advanced when placed there, and consequently had 

 been less exposed to the influence of the high tempera- 

 ture ; for they occupied only from 3 to 5 days in emerging, 

 instead of occupying 6 to 8 days, as the others did. 



Of the spring emergence, it will be noticed that the 

 first one was for as much as 14 days at a temperature of 

 80% and it is much lighter than the rest of the family, 

 which were not forced till February and March. It was 

 one of six which were forced in November, the other five 

 having died, an event which usually happens when the 

 spring emergence is forced early in autumn. 



Illiistraria. — Five families, two of them (Families "T" 

 and "E") of the spring emergence, comprising about 80 

 individuals. These were placed during their penultimate 

 pupal stage at three different temperatures, viz., at 80°, 

 at about 60°, and out of doors (emerging April and early 

 in May at a temperature averaging, during April, about 

 42°, or a little over). These last were generally darker 

 than those at 60°. Every one of those at either of the 

 lower temperatures is darker than any one of those at 

 80°, with the exception of one imperfectly develoiDed 

 specimen. 



Three families ("I," "J," and "Bed C") are of the 

 summer emergence, and comprise more than 80 indi- 

 viduals. Each of these families was divided, and the 



p2 



