INSECTA 105 



tasteful to birds; its red color gives notice of its undesira- 

 bility, and it generally is let alone. The viceroy lives 

 on the monarch's " reputation. " It is apparently of good 

 flavor, for it is readily eaten by birds if its color is rubbed 

 off. Its color and general appearance, however, are very 

 much like those of the monarch, and it is consequently 

 avoided by predaceous animals. Probably the commonest 

 butterfly in the United States is the cabbage butterfly, 

 Pieris rapce, which is white with black spots on its wings. 

 Its larva is the green caterpillar which is often so destruc- 

 tive to cabbages. 



Moths are of much more economic importance than 

 butterflies. Many species do injury and some are highly 

 beneficial. Among destructive larvae may be mentioned: 

 the web worm, on trees and shrubs, tent caterpillars (trees), 

 cotton worm, tobacco worm, army worm (garden crops), 

 boll worm (cotton), canker worm (fruit trees), codling 

 worm (apple), and the larvae of the gypsy (trees), tussock 

 (trees), clothes, flour, and grain moths. The larvae of the 

 brown-tailed moth has lately attracted considerable atten- 

 tion in the Eastern United States. A person who accident- 

 ally touches one of the caterpillars may have poisonous 

 hairs imbedded in the skin, and a festering eruption results. 



The silkworm, Bombyx mori, stands preeminent among 

 beneficial insects. This larva is fed on mulberry leaves and 

 after attaining its growth spins the cocoon in which it 

 becomes a pupa. This cocoon is the only source of com- 

 mercial silk. The silk industry originated in China but 

 the propagation of silk worms is now carried on in most 

 parts of the world where conditions are suitable. To ob- 

 tain silk, the cocoons are plunged into hot water and un- 

 wound, thus unraveling the fine threads which originated 

 in the spinning glands of the silk moth larva. Silk indus- 

 tries in the United States amount to about $100,000,000 a 

 year. 



