POTATO INSECTS 



147 



in earthen cells to pupse. The pupa is a little over ^ inch in 

 length and orange-yellow in color (Fig. 84). After a pupal 

 period of five to ten days the adults emerge. The beetle is 

 about f inch in length, strongly convex above and yellow in 

 color. The head has a triangular black spot between the 

 eyes ; the prothorax is marked with two divergent elongate 

 black spots near the middle and four to six smaller spots on 

 each side. Each wing-cover has the sutural margin and five 

 narrow stripes black, the second and third united at the tip; 

 the knees and tarsi are blackish (Fig. 85). The beetles are 

 often called hard-shells to distinguish them from the larvae, 

 which are known as slugs or soft-shells. 

 After feeding a few days, the beetles may 

 either go into the ground for a more or 

 less extended period of aestivation or they 

 may immediately lay eggs for a second 

 generation. Owing to the long period 

 over which egg-laying takes place, all 

 stages of the insect may be found at any 

 time during the latter part of the summer. 

 There are normally two generations pro- 

 duced annually but in some cases a small 



third brood of larvae may develop and in INIontana it is 

 claimed that there is only one generation. 



Fig. 85. — The Colorado 

 potato beetle (X 2§). 



Control. 



For many years paris green has been the standard insecti- 

 cide for the control of the Colorado potato beetle. It is some- 

 times applied in the form of a dust, 1 pound in 50 pounds of 

 land plaster or hydrated lime. It is more effective, however, 

 when applied in water, 1 pound in 50 gallons. To avoid burn- 

 ing the foliage, 2 pounds of lime should be added. Paris green 

 is most effective and least liable to injure the vines when ap- 

 plied with bordeaux mixture as used for the control of fungous 



