XVI. On some Variations observed in Bombyx Cynthia, 
in 1866. By ArtexanperR Wattace, M.D, 
M.R.C.P. 
[Read February 4, 1867.] 
Durine the summer of 1866 I bred over 4,000 specimens of 
Bombyx Cynthia. My first specimen came out on May 30th when 
the weather was temperate, about 55°—60° F. during the day: 
the last one emerged on August 8th: there was thus a period of 
seventy-one days between the first and last emergence. 
The cocoons were strung up in chaplets of fifty each, and sus- 
pended round the walls of a room which had an eastern aspect. 
Hence the sunshine fell during a portion of the day on some only 
of the cocoons. When the moths appeared, I noticed that the 
darkest and richest coloured specimens were invariably on the 
west wall, especially in the angle of the room which was the most 
remote from the light; one portion of cocoons, however, which 
had been allowed to retain their leafy covering produced the 
darkest specimens, whereas all the other cocoons had been de- 
nuded as far as possible of their leafy envelope. Hence I came to 
the conclusion that shade, during the pupa stage, is c@leris paribus 
most favourable to the production of the darker tints, whereas 
sunshine tends to diminish the intensity of coloration. The larvee 
which had spun their cocoons were freely exposed to the sunshine 
in 1865, being fed in the open air on a plantation of Ailanthus 
trees on arailway bank near Colchester. 
Another observation on coloration I was also able to make, that 
the earliest bred specimens were of a predominant olive-green 
ground-colour, whereas the later bred, and especially those that 
escaped from pupe in September, not having passed a winter in 
cocoon, were of a predominant yellow tint. Specimens of these 
tints are brought for exhibition. The three first males in the 
box are of the dark summer hue, and the fourth is a later and 
lighter tinted specimen. Exceptions of course occur to this rule, 
but they are very few. It is hardly necessary to observe, that 
these tints closely resembled the shades of the Ailanthus leaflets, 
