208 Dr. Wallace oz 
emerge ; some will be wasted at the beginning, some at the end 
of the season, some will be cripples. 
Again, of my main crop in 1865 of about 600 cocoons, 563 
moths emerged between May 22nd and July 27th; of these 20 
fertile pairs were obtained; their eggs laid from May 24th to 
July 26th were 37,000 in number, or about 160 eggs to each 
female, and about 65 eggs to each insect. 
The eggs are much larger than those of &. Mort (but that 
insect lays twice as many); they are about the size of the eggs of 
Lasiocampa Quercus or Odonestis Potatoria, are oval, equally large 
at both ends, white or greyish-white, and scantily marked with 
black spots or specks or streaks, owing to the particles of gum 
without (see Pl. XVI.j. When the eggs are near hatching they 
flatten a little, lose their weight and assume a greyish tint, pro- 
duced by the caterpillar inside ; when empty they still are of a 
greyish tint; the shell is very hard and tough, it is difficult to cut 
it with a knife, and will resist a considerable amount of pres- 
sure; when deposited it is covered during the act with a thin 
gum, which binds it tolerably firmly to adjacent objects; when 
the gum is dry the egg may easily be detached by pressure, and, 
if placed on moist paper, will adhere to the paper as if originally 
Jaid thereon. 
Various modes have been adopted to incubate the eggs ; some 
retain them in glass vessels, others in boxes, some in muslin bags 
attached to the tree; in all cases a slight amount of moisture 
must be rendered to imitate nature. ‘The simplest plan undoubt- 
edly would be to place them in muslin or paper bags on the tree, 
sheltered by some cover from rain and weather, so that when the 
young worms are hatched they may at once eat the living leaf as 
in a state of nature ; care must be always taken to number and 
mark the bags with the date of the deposition, and to keep all 
eggs of the same parcel as nearly as possible of the same date. 
Some have confined the fertile female among Ailanthus trees netted 
over, when she will readily deposit her eggs on the leaf-stalks ; 
others gum the eggs on paper, and cutting out a certain number 
attach these again to the tree. I prefer, however, as more con- 
venient and admitting of easier observation, the mode I have re- 
commended of keeping the eggs on bibulous paper under a glass 
funnel in a warm moist spot; and the night before they hatch 
out pinning on the tree a little paper or muslin bag, containing 
not more than 100 eggs; the pin which fastens the bag should be 
pushed into the leaf-stalk just below the base of a leaflet, and the 
leaflet folded down into the bag and there retained by a second 
