INSECTS. 



265 



other common name, hawk-moths, has reference to their 

 powers of flight. 



Another group of moths are known as Bombycids. 

 While some of these are unmitigated pests, others are of 

 value to man, the silkworms leading in this respect. These 

 are, in fact, the most valuable of all insects. The true 

 silkworm is a native of China, but has been distributed to 

 all of the warm parts of the earth. Like other caterpil- 



FIG. 83= Sphinx-moth (Everyx myron). From Riley. 



lars, they form their cocoons, and then these are heated 

 to kill the pupa and the silk of the cocoon is unwound, 

 and after proper treatment becomes the silk of commerce. 

 We have several species of silkworms in this country 

 some of which make a stronger silk than the Chinese 

 species; but although a few articles have been made 

 from it, it has no economic importance. These large 

 American silkworm-moths are known as Polyphemus-, 

 Prometheus-, Cecropia-, and lo-moths, and they, together 

 with the beautiful green Luna-moth, are great favorites 

 with collectors. 



The skippers are a group of small butterflies in which 

 the clubbed antennae are bent into a hook at the tip. They 

 are called skippers on account of their jerky flight. 



