HYBERNATION OF EGGS. 87 



an intimate connexion with heat in animated bodies. 

 The hving principle, to which we shall by and by 

 advert, must also be taken into account. 



In consequence of the minuteness of insect eggs, 

 notwithstanding the researches of enthusiastic ento- 

 mologists, we are still unacquainted with by far the 

 greater number. The hybernation of eggs is, there- 

 fore, a subject upon which little is known. In the 

 egg state insect life is, perhaps, less liable to acci- 

 dents, than in a more advanced stage of existence; 

 and it is most probable that the greater number re- 

 main unhatched during the cold season. Different 

 modes of depositing eggs are resorted to by different 

 species of the same genus, as may be exemplified in 

 the plant lice (^Jlphides). It was observed by De 

 Geer, that those of the birch and the blackthorn 

 {Aphis Alnij and A. Pruni) covered each egg indivi- 

 dually with a white cottony down, detached from their 

 bodies by means of their hind legs, and placed by the 

 same means over the eggs.* But the greater num- 

 ber of this family lay their eggs in an exposed situa- 

 tion, upon the plants where the young, when hatched, 

 may find food. Thus Kirby found the small black 

 eggs of a large species on the buds of birch-trees ; and 

 we have just discovered (Jan. 1830) a numerous de- 

 posit of the eggs of the magpie plant-louse {Aphis 

 Sambuci) on an elder tree, where the insect was 

 abundant the preceding summer. | These eggs are 

 exceedingly minute, but easily observed on account of 

 their shining black colour. They are placed in an ir- 

 regular patch upon the part of a trunk from which the 

 bark has been stripped off, and are entirely unprotected. 



The cochenille insects {Coccidce, Leach), so called 

 from one of the species furnishing the well-known 

 valuable dye-stuff, protect their eggs in a still more 



* De Geer, Mem. sur les Insectj?, iii, 48, 51. t J. R. 



