102 STATES OF INSECTS. (£gg.) 
tries where they are reared, the women effect their ex- 
clusion in a much shorter period by carrying them in 
their bosoms: yet to retard their hatching with particu- 
lar views is in many circumstances impossible. When 
the heat of the atmosphere has reached a certain point, 
the hatching cannot be retarded by cellars; and M. 
Faujas has remarked, that in June the silk-worm’s eggs 
would hatch in an ice-house ?. 
The period of exclusion does not, however, depend 
solely upon temperature : the hardness or softness of the 
shell, and possibly differences in the consistence of the 
included fluid, intended to serve this very purpose, cause 
some eggs to be hatched much sooner than others ex- 
posed to the same degree of heat. Thus the eggs of many 
flesh-flies are hatched in twenty-four hours®; those of 
bees and some other insects in three days; those of a 
common lady-bird (Coccinella bipunctata) in five or six 
days ; those of spiders in about three weeks ; those of the 
mole-cricket in a month; while those of many Lepidoptera 
and Coleoptera require a longer period for exclusion. 
The hard eggs of Trichoda Neustria and castrensis, 
noticed above, remain full nine months before being 
hatched *, as do those of another moth (Hypogymna 
dispar), which, though laid in the beginning of the warm 
month of August, do not send forth the included cater- 
* Young’s France, ii. 34. This author asserts, that no art will 
hatch the eggs of the common silk-worms the first year, or that in 
which they are laid; but that there is a sort brought from Persia, 
which are hatched three times a year, and which will hatch in fifteen 
days in the proper heat. In 1765, it is said, the common sort hatched 
in the first year. Ibid. 226—. 
> In the N. Dict. d’ Hist. Nat. xii. 564, the eggs of the flesh-fly 
are said to hatch in two hours. This is true I believe in very warm 
weather. © Brahm. 310. 
