Ailanthiculture. 209 
pin, so that the young worms on emerging at once crawl on to 
the tip of the leaflet, and being on its concave under-surface are 
protected equally from wind, wet and sun, and in a few days mi- 
grate further. 
There is a reason why I have restricted the number of eggs to 
100. I have frequently put more on, often 500, sometimes more 
than 1,000, but I have found that smaller quantities do better, 
because at first the young larve are very gregarious and the under 
surface of the leaf is so crowded that its green colour can scarcely 
be seen; it then happens that portions of the leaf are eaten off and 
fall to the ground, having small larve upon them, and these larvze 
mostly perish, Again, if there is much wind, leaf chafes against 
leaf, and the larvee at the edge fall down ; also during their moults, 
if too numerously crowded, those backward to change are eaten 
off*by their companions who have already moulted, and so tumble 
to the ground; once on the ground, very few when young re- 
ascend, but fall a prey to their enemies. Hence I advise not to 
put more than 100 eggs on a single leaf. 
The eggs will not I believe retain their vitality during the winter, 
as is the custom with L. Mori. Indeed it seems contrary to nature 
that an egg, which naturally emerges in about fourteen days, should 
retain its vitality uninjured during six months’ cold; however, I tried 
last winter to keep some eggs laid late in the autumn, in November; 
I placed them in a chip-box and exposed them out of doors to all 
weathers, but not one hatched out in the spring ; so in the previous 
winter I placed some in ice, but they all lost their vitality. Simi- 
larly in Guernsey Dr. Collins tried, but failed, to keep eggs alive 
during the winter, Though B. Mori may have an advantage over 
B. Cynthia in passing the winter in the egg-stage, inasmuch as 
it can more easily be carried from one country to another, and 
obtains a lengthened period for the sale of the eggs, yet I am 
inclined to think that as regards English Sericiculture it is better 
to possess a species which, like B, Cynthia, passes the winter in 
cocoon. For protected as it is by a stout silken cocoon, it needs 
but little other protection from winter’s frost and cold. Healthy 
and fine specimens emerged in the following summers, though ex- 
posed out of doors to the severe weather of 1863-4, 1864-5; it is 
possible that in the egg-state the insect may be less hardy. But 
further, the eggs of LB. Mori hatch out and require food early in the 
spring ; not so B. Cynthia, whose imago being the first to appear in 
the spring, more time is afforded for the development of the food 
of the larva; and whereas Z. J/ori requires sustenance in May and is 
killed by a temperature of 40° F, in the tender stage of the newly- 
