INSECTS AND OTHER ORGANISMS 



419 



The gypsy moth has been known as a pest for nearly two 

 hundred years. The larvae feed upon the foliage of many kinds 

 of forest and orchard 

 trees, ruining the plants 

 completely (see Figs, 220, 

 221). 



The codling moth is 

 familiar to everyone who 

 has found a wormy apple. 

 This insect is present 

 wherever apple trees are 

 grown, and in some re- 

 gions it destroys from 40 

 to 7 5 per cent of the crop 

 (see Fig. 222). 



The Hessian fly is so 

 called because it was sup- 

 posed to have come to 

 this country with the Hes- 

 sian soldiers during the 

 Revolutionary War. It 

 has spread to all parts of 

 the world, probably at- 

 tached in the pupal stage 

 to wheat straw used as 

 packing for merchandise 

 or as bedding for horses 

 and cattle. It has caused 

 great damage to wheat, 

 and it sometimes attacks 

 barley and rye. 



The San Jose scale 

 has been very destructive to fruit trees, attacking the leaves 

 and twigs as well as the fruit of many cultivated species. It 

 was introduced from China on some nursery stock and was 



Fig. 220. The gypsy moth [Poiihetiia dispar). 

 {a, b, c, shghtly enlarged ; d, shghtly reduced) 



This animal was introduced into this country about 

 i86g, in the course of some experiments made to 

 find a substitute for the silk moth, and in twenty 

 years it became so great a nuisance that the legis- 

 lature of Massachusetts made an appropriation for 

 the study of methods to be used in checking the 

 insect. In ten years over a million dollars was 

 spent in the fight, but further work was stopped 

 by some of the legislators whose regions had not 

 been affected. The insects then multiplied to such 

 an alarming extent that in 1906 about a quarter of 

 a million dollars was again spent in the fight. 

 a, male adult ; b, female ; c, larva ; d, pupa 



