GENERAL CROP PESTS 



89 



The Onion Thrips (Thrips tabaci Lind.). — Few gardeners 

 are unacquainted with "thrips," of which there are several 

 species injurious to plants grown under glass. The commonest 

 and most destructive vegetable-feeding species in America are 

 the onion thrips and the wheat thrips. 



All thrips are exceedingly minute, the common species not 

 exceeding one-twentieth of an inch in length. They have 



Fig. 50. — Onion thrips. a, Adult; b, antenna of same; c, young larva; d, fuU-grovm 

 larva— greatly enlarged. (Howard, U.S. Dept. Agr.) 



elongate bodies, and the winged lorms have four very slender 

 wings fringed with long, delicate hairs. These insects are 

 somewhat anomalous in the manner of their feeding: their 

 mouth-parts are fitted chiefly for sucking, but they also have 

 bristle-like mandibles. 



The general appearance of the onion thrips is shown in 

 figure 50, Oj highly magnified. It is pale yellow, with the thorax 

 somewhat darker. The wings are paler yellow, with dusky 

 fringes and bristles. 



The parent insects are usually found on the lower sides of 

 leaves or imbedded in flowers of various kinds. In their attacks 

 they induce the withering of the parts affected, and they some- 

 times destroy entire plantings. The onion thrips injures a great 

 variety of field and garden crops, to which it is quite as de- 

 structive as to plants grown artificially. Besides onion it in- 

 juriously affects garden leek, parsley, cabbage, celery, melon, 



