FORMS OF EGGS. 



41 



the true cause of the varied forms of the eggs of in- 

 sects. 



Eggs of a butterfly and of a moth, magnified. 



The cause of the eggs of birds being nearly the 

 same in shape, arises, we should say, from the similar 

 forms of the animals themselves; while insects being 

 much more varied in shape, require corresponding 

 varieties in the forms of their eggs. The ostrich, 

 the eagle, and the wren, for example, differ much 

 more in size than in their general form; but the 

 earwig, the garden-spider, butterflies, beetles, and 

 grasshoppers, differ much more in form than in size, 

 and consequently require eggs of varying forms to 

 contain their progeny. We confess, however, that 

 we cannot always trace the mathematical causes of 

 these diversities of form in the eggs of insects; for 

 though there prevails a general resemblance in those 

 families and groups the most nearly allied, yet in 

 others, even the species of the same genus exhibit 

 differences which cannot be thus accounted for. In 

 two species of Vanessa, for instance, the small and 

 the great tortoise-shell butterflies, which differ in 

 little but size, the egg of the small is cylindric with 

 eight prominent ribs, while that of the great is shap- 

 ed like a Florence flask, and quite smooth and uni- 

 form.* 



The ribbing of the eggs of the small tortoise-shell 



* Sepp, der Wonderen Gods, Tab. ii, and viii. 

 VOL. vi. 4* 



