10 



CnRTSOMELIM. 



The beetle winters as an imago in the soil, or under leaves, 

 stones, etc. The eggs are laid in heaps on the leaves, mostly 

 on their lower sides, but also on the stalks ; they are slightly 

 stuck together, and each heap contains from five to twenty-five 

 or more eggs. The egg stage lasts four days, the larva stage 

 eighteen to twenty-one and the pupal ten to twelve days ; the 

 larva burrows into the earth to a depth of about half an inch to 

 pupate. The principal damage is done by the larvse, which live 

 in colonies and pass from one plant to another. The imagines 

 clo not fly readily, and remain on the mustard until it has been 

 cropped ; they then pass to cruciferous weeds or vegetables. 

 The beetles also do much harm to cabbages early in spring by 

 destroying the terminal buds. 



North America. 



The Colorado Beetle, Leptinotarsa decemlineata, Say. 



The history of how this insect became a pest in America is 

 interesting. It was a native of the Rocky Mountain region, and 

 until about 1855 was satisfied with feeding upon various common 

 weeds of the same genus (that is, Solanum) as the potato-plant, 

 and of closely-allied genera. With European immigration and 

 the consequent introduction and cultivation of the Irish potato, 

 the balance of Nature was disturbed. The beetles, finding large 

 quantities of food easily available, began to make the potato 

 patch their feeding-ground, and rapidly spread eastward. It must 

 also be remembered that they were beinpr continually transported 

 by the shipping of potatoes. In 1859 they had readied a point 

 one hundred miles west of Omaha, and in 1864 they crossed 

 the Mississippi into Illinois. They advanced steadily eastward 

 till they were recorded from the Atlantic States in 1874. To- 

 day they are found wherever the potato is cultivated in the United 

 States and Southern Canada. 



Lije-liistory. — In the month of October the beetles go under- 

 ground, where they hibernate till April or May, when the warm 

 weather brings them out. When the food-plant appears above 

 ground, the females lay their yellow eggs on the underside of the 

 leaves near the tips. On an average a female can lay about five 

 hundred eggs during the course of a month. Meanwhile the 

 adult beetles have done considerable damage by eating the young 

 and tender plants. A large number of larva? hatch out within a 

 week and eat ravenously, increasing in size considerably and very 

 rapidly. The larval life covers a period of about two and a half 

 to three weeks, by which time the larvse are full-grown and enter 

 the earth, where they form smooth, oval cells in which they 

 undergo their metamorphosis. The adult beetles emerge in about 

 a week or two and, after feeding for a couple of weeks, deposit 

 eggs for a second generation. Throughout the districts where the 

 insect is most injurious there are two generations a year, but 

 farther south there may be at least a partial third generation, 

 and in the north the species has but one generation a year. 



