/VRTIIROPODA 



215 



There is one group of moths, however, which are very valu- 

 able, — the silkworm moths; of these there are about a dozen 

 species. The largest and strongest of the domesticated species 

 is the Chinese silkworm, Bombyx 111011 (Fig. 217), which feeds 

 on the mulberry and produces a very fine thread. It is exten- 

 sively cultivated in Asia and Europe. The cocoon is white or 

 yellowish white, and about three centimeters long by nearly halt 



: "T^-C- ; ? '■' *v^-' r~— \ 





Fig. 217. Bombyx mori, the silkworm moth, male and female. (After Shipley and Mac- 

 Bride.) 



as broad. The most hardy silkworm in the United States is 

 Telea polyphemus, which feeds on the oak. The silk is coarser 

 than that of the Chinese worm, but has a rich gloss, and is readily 

 unwound from the cocoon. 



Order 7. Diptera 



The Diptera (Gr. St?, two, and irrepov, wing) include all the 

 flies, properly so called, such as the common house fly, the horse- 

 fly, the long-legged crane fly, the mosquito, and many others. 

 They have only a single pair of wings, which are thin, transpar- 

 ent and membranous, and attached to the mesothorax ; the pos- 

 terior wings are represented by knobbed, threadlike processes, 

 borne on the metathorax, and called the halters. The mouth 

 parts are adapted to piercing and sucking, and the metamorpho- 

 sis is complete. This order has a wider geographical distribu- 

 tion than any other group of insects. A few flies are parasitic 

 in the adult state, such as the sheep tick, the horse louse, and 

 others which live on bats and some birds. The larva 1 are en- 

 tirely without feet and develop in various places ; some feed on 

 animals, some are known as maggots and suck up fluids or semi- 



