INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 57 



appearance. The fruit may be scabbed and curled or otherwise deformed 

 by the constant chafing. 



Life History.— As stated above, the eggs are inserted in the stem, 

 leaf or small fruits of the host. They hatch in from four to five days, 

 the larvas or "white thrips" beginning to feed at once and to do 

 damage. When full grown, which takes from two to three weeks, these 

 drop to the ground and after penetrating several inches enclose them- 

 selves in a small earthen cell, where they remain throughout the trans- 

 forming or pupal period. This period usually begins about September 

 and continues throughout the months of October, November and 

 December, when adult insects are formed. These remain in the ground 

 until February before emerging. The transformation from the larval 

 to the adult stage occupies several months, the slow growth being prob- 

 ably due to the cold winter season. 



Nature of Work. — The chief injury by this species is to the blos- 

 soms, so many of which may be destroyed as to greatly reduce or entirely 

 eliminate the crop. 



Distribution.— According to Paul R. Jones, formerly in charge of 

 the pear thrips investigations in California for the United States Depart- 

 ment of Agriculture, the pear thrips are now reported only in parts of 

 the following counties: Ala- 

 meda, Contra Costa, Napa, ^ 

 Sacramento, San Benito, San 

 Joaquin, Santa Clara, Solano, 

 Sonoma and Yolo. 



Food Plants.— This insect 

 is particularly a deciduous 

 tree pest and works great 

 damage to the leaf and flower 

 buds, as well as to the young 



fnm"+ TIio inifiol ^o mo « Q ic Fig - 49 - — The pear thrips, Taniothrips pyri 



irillt. lUe initial damage IS (Daniel). Head and tip of the abdomen. (After 



done just before or after Mouiton, u. s. Dept. Agric.) 

 blossoming time. The pear suffers probably more than any other tree 

 due to ravages of this insect, although prunes and plums are also 

 severely attacked. Almonds, apricots and peaches also receive serious 

 damage some seasons. The following are other hosts of this pest: 

 apple, cherry, fig, grape and English walnut. 



Control. 33 — Government Formula: The formula which has given 

 the best results is made up of the 3 per cent distillate oil emulsion, to 

 which is added from 1 per cent to If per cent of tobacco extract No. 1 

 (black leaf containing 2.75 per cent nicotine) or tobacco extract No. 2 

 (sulphate of nicotine or black leaf 40), which is 40 per cent nicotine, 

 at the rate of 1 part to from 1,500 to 2,000 parts of the spray mixture. 

 The distillate oil emulsion may be obtained from several dealers in 

 chemical and spraying supplies, or may be made at home. By the 

 use of the home-made emulsion, a considerable proportion of the cost 

 of spraying is often saved, and, what is more important, the quality 

 of the emulsion is above reproach, when good materials are properly 

 used in its manufacture and the emulsion properly made. 



S3 By Paul R. Jones, San Jose, Cal. 



