348 



A COURSE ON ZOOLOGY. 



produce other eggs, which are preserved until the follow- 

 ing season. Twenty ounces of cocoons yield about an 

 ounce of eggs. The cocoons from which silk is to be 

 made are exposed to steam ; the pupa are thus killed, 

 and the silk is unrolled and reeled. 



The sericaria mori, or bombyx mori, which produces 

 the best silk, can be reared only where the mulberry 

 flourishes, but there are other silk-producing worms, 

 species of bombyx, that feed on oak-leaves, rice-leaves, 

 and on the leaves of poplar, elm, white thorn, and cas- 

 tor-oil bean. 



The cochineal insects are species of hemiptera in which 

 FIG. 311. 



COCHINEAL (Coccus cacti). a, living on cactus (Opuntia) ; b, male ; c, female. 



the female lives flattened out on the leaves of certain 

 plants ; as soon as the eggs are laid she swells up and 



