100 STATES OF INSECTS. (Ege.) 
ranged like tiles on a roof one laid partly over another, 
on the under side of the leaves of the water-plantain, from 
white become green, and then change to olive green. 
Those of the hemipterous enemy of the larch, more than 
once mentioned in this letter, are first mouse-coloured, 
then they assume a reddish hue, and lastly a blackish 
one. Those of the gnat from white in a short time as- 
sume a shade of green, in a few hours they are entirely 
green, and at length become gray*. ‘Those of the silk- 
worm, which at first are of a yellow or sulphur colour, 
acquire a violet shade. ‘The eggs of that rare and beau- 
tiful moth Endromis versicolor, are at first sulphur-co- 
loured, then green, next rose-coloured, and _ lastly 
blackish. The colour of almost all eggs changes when 
they are near hatching; but this change depends more 
frequently upon the colour of the included larva, which 
appears through the transparent shell of the egg, than 
upon any actual alteration in the egg itself. 
vill. Period of hatching. The general rule for the 
hatching of the eggs of insects is the absorption by the 
embryo of all the superabundant moisture included in 
them ; but the time varies according to the state of the 
atmosphere, to the action of which they are subjected. 
Like those of other animals, they require a certain degree 
of heat for the due evolution of the included larva. This 
heat in much the greater number of instances is derived 
from the temperature of the air, but often also from 
other sources. The eggs of the gad-fly tribe are hatched 
principally by the heat of the body of the animal to which 
they are committed ; and doubtless the vital heat of va- 
 Reaum. iy. 617. 
