56 INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 



are numerous on the foliage. In spraying for this insect it is advisable 

 to use angle nozzles and from 175 to 200 pounds pressure, care being 

 taken that every portion of the tree is thoroughly drenched. The spray- 

 ing for this species in California, however, has not proven profitable 

 enough to justify its continuance, except in nurseries. 



THE ONION THRIPS 



Thrips tabaci Lindeman (Family Thripidse) 



Description. — The adult female is pale yellow in color with an 

 elongated dusky spot on the dorsal surface of the middle thoracic seg- 

 ment . The length of the body varies from -fa to -jV inch. The eyes are 

 brown, while the antennae and legs are dusky. The wings are faintly 

 yellowish, their fringes being dusky. The antennae are seven jointed. 

 The male larvae are somewhat smaller than the female and of a 

 darker color and often with a greenish tint. The eyes are red. 



Life History.— The life history is practically the same as that of 

 the bean thrips. 



Nature of Work. — The constant chafing of the thrips upon the 

 leaves produces countless numbers of small white or silvery spots which 

 are very noticeable. The growth of the plant is often stunted by the 

 attacks. 



Distribution. — This species is generally distributed throughout the 

 entire State. It is often very troublesome to onion growers in the warm 

 interior valleys and in the Imperial Valley. 



Food Plants. — The onion thrips is especially destructive to onions 

 grown for seed. It damages the seed buds before the seeds have hard- 

 ened and in many instances causes a complete failure of the seed crop. 

 It is also destructive to cabbage, fruit trees, grass, muskmelon, pigweed, 

 sunflower and many truck crops. 



Control.— The remedies are the same as for the bean thrips. 

 Natural Enemy.— The internal hymenopterous parasite, Triph- 

 octt nus russelli Crawford, has also been reared from this species. 32 



THE PEAR THRIPS 



Twniothrips pyri (Daniel) (Family Thripidae) 



(Euthrips pyri Daniel) 



(Fig. 49) 



Description. — The eggs are very minute, white and bean-shaped. 

 They are embedded in the tender tissues of the host, The first born 

 larvae are white, with distinct red eyes, and move slowly. They are often 

 very thick on the trees and are known as "white thrips." Pupation 

 takes place in the ground, the pupae being white and seldom met with 

 except by careful investigation. The adult insect is dark in color, vary- 

 ing from an amber to a dark brown or almost black and about 1-20 inch 

 long. The presence of this species is usually told by ravages on the 

 tender tissues of the expanding flowers and leaf buds' and later by the 

 attacks on the young fruit, In badly infested orchards the buds 'often 

 fail to open and the whole orchard may present a brown fire-swept 



"Russell, TI. M., Tech. Ser. M. 23, Pt. II, Bur. Ent. U. S. Dept. Agric, 1912. 



