122 



APPLIED ENTOMOLOGY 



occurs. Rotation of crops has proved a successful control for this insect in 

 practically every case where it has been tried. 



Another species (Diabrotica vergifera Lee.) having similar habits and similarly 

 controlled, is often destructively abundant in Colorado. 



On the Pacific Coast a different species, the Western Twelve-spotted Cucum- 

 ber Beetle or Flower Beetle (Diabrotica soror Lee.), appears to have the same gen- 

 eral habits as its eastern relatives, but observations thus far indicate that the 

 grubs are injurious mainly to alfalfa, beet, pea and peanut roots, while the adults 

 do much damage to many plant leaves, buds and flowers. The winter appears 

 to be spent in the adult stage and the eggs are laid from March to May in 

 different latitudes. There are probably two generations each year. The adult 

 is one-fifth to one-fourth of an inch long. The head, antennae, legs and body are 

 black; the pronotum and elytra green or yellowish, the latter with twelve black 

 spots often partly fused. Control thus far has been directed mainly against the 

 beetles, spraying plants on which they are feeding with arsenate of lead (neutral) 

 at the standard formula, using either water or Bordeaux mixture. 



FIG. 113. Adult Flea Beetles: a, Spinach Flea Beetle, enlarged nearly five times; 

 6, Potato Flea Beetle, enlarged about seven times; c, Egg-plant Flea Beetle, enlarged about 

 seven times. (From U. S. D. A. Bulletins.) 



Flea Beetles. Many tiny beetles belonging in the Chrysomelidse 

 are known as Flea beetles because when disturbed they hop away like 

 fleas. The economic forms vary in size from about a fifth to a fifteenth 

 of an inch in length (Fig. 113). Most of them are blackish or steel- 

 blue, though some have portions of the body yellow, whitish, red or 

 other colors. The hind femora are very large, enabling the insects to make 

 vigorous leaps. The adults feed on the leaves, eating tiny holes, while in 

 most cases the Iarva3 are root feeders, generally on the same plants which 

 their adults attack, though in some cases they also attack the leaves. 

 Many attack garden crops such as the potato, turnip, beet, spinach, 

 rhubarb and radish, while other species feed on the strawberry, grape, 

 tobacco, hop, clover, apple, Virginia creeper, willow, alder, etc. In most 

 cases there are two generations a year, the first appearing early in the 

 season and the second in mid-summer or early fall, though some species 

 have but one generation and some have several. 



Control. These insects which are often serious pests, appear to be 

 repelled by Bordeaux mixture, but it is better to combine this with 



