INSECTS INJURIOUS TO POTATOES AND TOMATOES 261 



History. As is probably known to most of the older genera- 

 tion who watched its spread eastward, the Colorado potato-beetle, 

 as its name indicates, was a native of the Rocky Mountain region, 

 and until about 1855 was satisfied with feeding upon various com- 

 mon weeds of the same genus as the potato-plant, principally 

 Solanum datura, and closely allied genera. But with the settle- 

 ment of this country and the introduction of the Irish potato, 

 these bugs also began to take advantage of the fruits of civilization 

 and transferred their feeding-grounds from the roadside to the 

 potato-patch, and rapidly spread eastward from one to another, 

 as well as being transported in the shipping of the potatoes. 



Thus, in 1859 they had reached a point one hundred miles west 

 of Omaha, Neb. ; five years later they crossed the Mississippi into 

 Illinois; and they advanced steadily eastward till recorded in 

 the Atlantic States in 1874. Though slow to be introduced into 

 some few sections of the country, it is safe to assert that this pest 

 may to-day be found almost wherever the potato is grown in the 

 United States or southern Canada. 



Life History. During October the beetles enter the earth and 

 there hibernate till the warm sunshine of April or May brings 

 them forth. As soon as the young plants appear, the female 

 beetles deposit their yellow eggs upon the underside of the leaves 

 near the tips, each female laying an average of about five hundred 

 eggs during the course of a month. Meanwhile the beetles have 

 done considerable damage by eating the young and tender plants. 

 In about a week there hatch a horde of very 

 small but very 'hungry larvae, which fairly 

 gorge themselves with potato-foliage and 

 increase in size with astonishing rapidity. 

 In two and a half to three weeks, after 

 having eaten an amount of food out of a 

 all proportion to their size, the larvae become FIG. 223. _ a, beak of pre- 



full grown, and enter the earth, where they daceous bug; 6, Podi- 

 . , ,, , sus spinosus Dall.; c, 



form smooth, oval cells, and transform to beak of plant-feeding 



ft 



pupae. In a week or two the adult beetles bu S- ( After 

 emerge from the pupal skins and after feeding for a couple of 

 weeks, deposit eggs for a second generation, which develops in 

 the same way, and the beetles from which hibernate as already 

 described. Throughout the territory where the beetles are most in- 



