Of these 20 butterflies only 5 were of the pure Prorsa form.
10. Full grown larvæ of the fourth generation, found on August 20th, 1870, pupated on August 26th to September 5th. The pupæ were divided into three portions:—
A. Placed in the hothouse (12°-25° R.), immediately after pupation and left there till October 20th. Of about 40 pupæ only 4 emerged, 3 of which were Prorsa and 1 Porima. The remaining pupæ hibernated and all changed into Levana the following spring.
B. Kept in a room heated to 6°-15° R. from November. Not a single specimen emerged the same year. This lot of pupæ were added to C from November.
C. Placed on ice for a month immediately after pupation; then, from September 28th to October 19th in the hothouse, where no more butterflies emerged. The pupæ hibernated, together with those from lot B, in a room heated by water to 6°-15° R., and gave:—
| On the | 6th | of February, | 1 | female Levana. |
| ” | 22nd | ” | 1 | male Levana. |
| ” | 23rd | ” | 1 | male Levana. |
| ” | 24th | ” | 1 | female Levana. |
| ” | 25th | ” | 1 | male and 1 female Levana. |
| ” | 28th | ” | 1 | male and 1 female Levana. |
| ” | 1st | of March, | 1 | male Levana. |
| ” | 13th | ” | 1 | female Levana. |
| ” | 15th | ” | 1 | female Levana. |
| ” | 19th | ” | 1 | male Levana. |
| ” | 2nd | of April, | 2 | male and 1 female Levana. |
| ” | 7th | ” | 1 | female Levana. |
| ” | 21st | ” | 1 | female Levana. |
| ” | 2nd | of May, | 1 | female Levana. |
| Total | 18 | Levana, 10 of which were females. | ||
The exact record of the time of emergence is interesting, because it is thereby rendered apparent that different individuals respond more in different degrees to a higher than to the ordinary temperature. Whilst with many an acceleration of development of 1–2 months occurred, others emerged in April and May, i.e. at the time of their appearance in the natural state.
11. Reared the second generation from eggs of the first generation. Emerged from the eggs on June 6th, 1872, pupated on July 9th. The pupæ were placed on ice (0°-1° R.) from July 11th till September 11th, and then transferred to a hothouse, where all emerged:—
| On the | 19th | of September, | 3 | male Prorsa, 1 male Porima. |
| ” | 21st | ” | 13 | Porima (12 males, 1 female), 2 female Levana. |
| ” | 22nd | ” | 14 | Porima (12 males, 2 females) and 1 female Levana. |
| ” | 23rd | ” | 10 | female Levana, 3 male Porima. |
| ” | 24th | ” | 5 | female Levana. |
| ” | 25th | ” | 1 | female Levana. |
| ” | 27th | ” | 3 | female Levana. |
| ” | 4th | of October, | 1 | male Porima. |
| Total | 57 | butterflies (32 males and 25 females), | ||
| only 3 of which were Prorsa, 32 Porima, and 22 Levana. | ||||
It must be pointed out, however, that among those specimens marked as “Levana” there were none which entirely corresponded with the natural Levana, or which indeed approximated so nearly to this form as did some of the specimens in Exp. [9]. All were larger than the natural Levana, and possessed, notwithstanding the large amount of yellow, more black than any true Levana. In all artificially bred Levana the black band of the basal half of the hind wings is always interrupted with yellow, which is seldom the case with true Levana. The whole appearance of the artificial Levana is also coarser, and the contour of the wings somewhat different, the fore-wings being broader and less pointed. (See figs. 7 to 9, [Pl. I].).