Exp. 1.—In 1877 chrysalides of P. Ajax and Grapta Interrogationis (the eggs laid by females of the form Fabricii) were experimented upon; but the results were not satisfactory, for the reason that the author having been absent from home most of the time while the pupæ were in the ice-box, on his return found the temperature above 5°-6° R. And so far as could be told, the ice had been put in irregularly, and there might have been intervals during which no ice at all was in the box. Six chrysalides of the Grapta so exposed produced unchanged Umbrosa, the co-form with Fabricii. But all chrysalides from the same lot of eggs, and not exposed to cold, also produced Umbrosa. Nothing was learnt, therefore, respecting this species.
But chrysalides of Ajax, exposed at same time, did give changed butterflies to some extent. From a lot of 8, placed in the box when under twelve hours from pupation, and left for twenty-four days, there came 5 males and 3 females. Of these was 1 Telamonides in markings and coloration, and all the rest were between Marcellus and Telamonides. Two other chrysalides on ice for twenty-three days gave Telamonides, but 3 more exposed twenty-six days, and all one hour old when put on ice, were unchanged, producing Marcellus.
During the same season 6 other Ajax chrysalides were placed in the box, and kept at about 0°-1° R. One was one hour old, and remained for five days; 1 was one hour old, and remained for two days and three-quarters; 3 at three hours old for eight days; and 1 (age omitted), six days. All these gave unchanged butterflies of the form Marcellus.
Exp. 2.—In May, 1878, many chrysalides were placed in the ice-box, being from eggs laid by Ajax, var. Walshii. The youngest were but ten to fifteen minutes from pupation, and were soft; others at intervals up to twenty-four hours (the chrysalis is hard at about twelve hours); after that, each day up to eight days after pupation. All were removed from the box on the same day, 28th May. The exposure was from nineteen to five days, those chrysalides which were put on ice latest having the shortest exposure. The author wished to determine if possible whether, in order to effect any change, it was necessary that cold should be applied immediately after pupation or if one or several days might intervene between pupation and refrigeration. Inasmuch as no colour begins to show itself in the pupæ till a few hours, or at most a day or two, before the butterfly emerges, it was thought possible that cold applied shortly before that time would be quite as effective as if applied earlier and especially very soon after pupation. The result was, that more than half of the chrysalides exposed before they had hardened died: 1 exposed at ten minutes, 2 at one hour, 1 at two hours, 2 at three hours after pupation. On the other hand 1 at fifteen minutes produced a butterfly, 1 at two hours, another at twelve hours. The temperature was from 0°-1° R. most of the time, but varied somewhat each day as the ice melted. The normal chrysalis period is from eleven to fourteen days, in case the butterfly emerges the same season, but very rarely an individual will emerge several weeks after pupation.
On the 14th day after taking the pupæ from the ice, 1 Telamonides emerged from a chrysalis which had been placed in the ice-box three days after pupation, and was on ice sixteen days.
On 19th day, 1 Telamonides emerged from a pupa put on the ice twelve hours after pupation, and kept there eleven days.
On 19th day, 1 Walshii emerged from a pupa two hours old, and on ice eleven days.
All the rest emerged Marcellus, unchanged, but at periods prolonged in a surprising way.
| 1 on | 43rd | day exposed | 15 minutes | after pupation. |
| ” | 46th | ” | 2 hours | ” |
| ” | 53rd | ” | 24 hours | ” |
| ” | 62nd | ” | 6 days | ” |
| ” | 63rd | ” | 4 days | ” |
| ” | 66th | ” | 7 days | ” |
| ” | 77th | ” | 4 days | ” |
| ” | 81st | ” | 12 hours | ” |
| ” | 91st | ” | 5 days | ” |
| ” | 96th | ” | 19 hours | ” |
Five chrysalides lived through the winter, and all gave Telamonides in the spring of 1879.
It appeared, therefore, that the only effect produced by cold in all chrysalides exposed more than three days after pupation was to retard the emergence of the butterfly. But even in some of these earliest exposed, and kept on the ice for full nineteen days, the only effect seemed to be to retard the butterfly.
Exp. 3.—In June, 1879, eggs of the form Marcellus were obtained, and in due time gave 104 chrysalides. Of these one-third were placed in the ice-box at from twelve to twenty-four hours after pupation, and were divided into 3 lots.