66 INTRODUCTION. 



attaching them to the plant and defending tit em 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 urticce, 

 with several longitudinal ridges- Fig. 4, Subconical 

 egg of Pontia brassicce, 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, 

 (egrria, 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. Tbis 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, 



