66 
INTRODUCTION. 
attaching them to the plant and defending them from 
the action of the weather. They differ essentially from 
the eggs of birds, as no lime enters into their composi- 
tion, and, instead of being covered with a crustaceous 
shell, they are merely enveloped by a thin membrane. 
They are. also very unlike each other in different 
species, whether we regard them in respect to co- 
lour, form, or sculpture. Some of them are nearly 
orbicular or oval, others cylindrical, and not a few 
conicaL The surface is often beautifully carved, as 
will be seen by the accompanying figures, which re- 
present several varieties, as they appear when highly 
magnified. Plate I. fig. 3, Egg of Vanessa urticm , 
with several longitudinal ridges. Fig. 4, Subeonical 
egg of Pontia brassica, with granulated longitudina, 
ribs, connected by elevated cross lines ; the colour 
bright yellow. Fig. 5, Egg of Hipparchia Tithonus. 
Fig. 6, Of Hipparchia Jurtina, crowned with a se- 
ries of imbricated scales. Fig. 7, Globular egg of 
Hipp. Hyperanthus, ornamented with regular rows 
of minute elevated points. Fig. 8, Egg of Hipp. 
(cge.ria, having the whole surface covered with hex- 
agonal meshes. 
After the fly has fixed her eggs on a plant, she 
takes no further care of them, but leaves them to be 
hatched by the heat of the atmosphere. This gene- 
rally takes place in the course of a few days, but the 
period varies according to the degree of warmth to 
which they are subjected, and the greater or less 
density of the shell or outer covering. Such, indeed, 
