THE LEPIDOPTERA 255 



loose bark or in crevices. These eggs hatch about the time the leaves 

 open and the larvae feed during about the same period as the other species, 

 and enter the ground to pupate at nearly the same time. This insect 

 also has the habit of spinning down on a thread when disturbed. 



Control of Canker Worms. The wingless condition of the females 

 which necessitates their crawling up the trunks of the trees in order 

 to reach the places where their eggs are laid, offers an opportunity 

 for control by banding the trunks, in the fall for the Fall Canker Worm, 

 and at the first warm days after winter has broken (even in February 

 in New England, in some seasons) for the spring species, either with 

 sticky bands which the insects are unable to cross, or with loose fluffy 

 cotton in which they become entangled. Care should be taken to keep 

 the bands fresh or in order so that no gaps through which they can crawl, 

 or bridges of their dead bodies over which they can cross, are formed. 

 If the caterpillars are already feeding when their presence is discovered, 

 spray with arsenate of lead, standard formula. 



FIG. 256. Silk Worm (Bombyx mori L.) : adult moth and its cocoon. About natural size. 



(Original.') 



Family Bombycidse (True Silk Worms). The only representative of 

 this family in North America is the Silk Worm (Bombyx mori L.) intro- 

 duced many years ago because of the silk obtained from its cocoon. 

 It does not appear to have established itself anywhere in this country 

 and silk-raising has not proved profitable here because of the cost of 

 the labor required, as compared with that in the Orient. 



The adult moth (Fig. 256) spreads about an inch and three-quarters 

 and is creamy-white in color, with two or three faint lines across the fore 

 wings. The larvae feed on the leaves of the mulberry and Osage orange 

 trees, and when full-grown leave their food and spin their cocoons (Fig. 

 256). When spinning has been completed these are gathered and the 

 insects within are killed by heat or fumigation. Now the loose silk of the 

 outside is removed and the cocoons are ready to market. Nearly 

 73,000,000 Ib. of raw silk were produced in the world in 1918, and the 

 importance of the industry is enormous. 



