INJURIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 271 



Nature of Work. — The adults are leaf eaters and their work is easily 

 recognized by the fact that the beetles are usually to be found where the 

 damage is done. Occasionally only the epidermis of the leaves is 

 devoured, but more often holes are eaten through and irregular portions 

 around the edges or the entire leaves are devoured. Buds and open 

 flowers are also injured in the same manner. The work of the larva? 

 is more difficult to ascertain and requires a close examination of the 

 roots of dead or dying plants to find the grubs at work. They eat the 

 roots from the outside and do not bore into them, as does the Eastern 

 species (Z>. 12-punctata). 180 



Distribution. — This is an exceedingly common beetle throughout the 

 entire State. 



Food Plants. — This species is a very general feeder, the adults 

 having been observed eating the foliage of the following plants: alfalfa, 

 bean, clover, beets, citron, cucumbers, cabbage, squash, muskmelon, 

 watermelon, corn, peas, peanut, potato, spinach, lettuce, lemon, mustard, 

 apricot, orange, prune, weeds and many other plants. The buds and 

 flowers of the rose, chrysanthemum, daisy, aster, zinnia and other orna- 

 mentals are also often seriously injured or entirely destroyed. The 

 larvae also work upon the roots of many plants and have been observed 

 upon the following : peanut, pea, alfalfa and beet. Nearly every year 

 the beetle has proven to be quite a serious pest in one or more localities 

 in the State. 



Control. — When necessary, control measures must be applied with 

 promptness and thoroughness to prevent loss. Arsenate of lead (neu- 

 tral preferred, because it does not burn foliage) at the rate of from 6 

 to 10 pounds to 100 gallons of water and a combination spray of 

 arsenate of lead and Bordeaux mixture (6 pounds of arsenate of lead 

 to 100 gallons of Bordeaux mixture) have each given good results, as 

 reported by H. O. Marsh. 181 



Natural Enemies. — The two common natural enemies of this beetle 

 are the tachina fly, Celatoria diabroticm Shim., 182 the maggots of 

 which live within and destroy the adult beetles, and a spider, Xysticus 

 gulosus Keys. 183 



THE TWELVE-SPOTTED CUCUMBER BEETLE OR SOUTHERN 



CORN ROOT-WORM 



Diabrotica 12-punctata Olivier 184 



(Fig. 262) 



Description. — The adults of this species greatly resemble the 

 Western species (D. soror), but are somewhat larger, a little paler green 

 in color, with the twelve black spots on the elytra distinctly separated 

 and seldom run together, as often occurs in the markings of the latter. 

 The head is black and the body light green or yellow. The first three 

 joints of the antenna? and the bases of the femora are yellow, the 

 remainder being very dark or black. The eggs are pale yellow, oval, 



""Chittenden. F. H., Bui No. 82. Pt. VI. Bur. Ent. U. S. Dept. Agric., pp. 71-75, 1910. 



ls 'Bul. No. 82, Pt. VI. U. S. Dept. Agric, pp. 81-82, 1910. 



182 Coquillett, D. W., Insect Life II, pp. 233-236, 1890. 



,s:, Coquillett, D. W., Insect Life II, p. 74, 1889. 



'"This species does not occur in the State, according to Dr. Van Dyke. 



