246 MANUAL OF VEGETABLE-GARDEN INSECTS 



The onion thrips passes the winter in both the adult and 

 nymphal state on onion plants left in the field. It is also 



probable that the thrips 



Fig. 



148. — The onion thrips, adult 

 female (X 30). 



hibernates in the rubbish 

 around the edge of the field, 

 since the infestation usually 

 begins along the weedy 

 borders and gradually 

 spreads over the remainder 

 of the field. 



The adult female thrips 

 (Fig. 148) is about ^ inch 

 in length and varies from 

 light yellow to brownish 

 yellow in color. The wings are long and narrow and bear on 

 the hind margin a fringe of long hairs. The male is rarely 

 found and the females normally reproduce with- 

 out being fertilized. The egg is translucent 

 white, irregularly bean-shaped and about t^ 

 inch in length. It is inserted nearly its full 

 length into the tissue of the leaf; the tip of 

 the smaller end projects slightly above the 

 surface. The eggs hatch in five to ten days, 

 the longer period being the more common. 

 The newly hatched nymph is about 5V inch in 

 length and translucent white in color with the 

 eyes bright red (Fig. 149). After feeding, the 

 body assumes a greenish color from the ingested 

 food. The first stage lasts about two days but in 

 some cases the period is longer. In the second 

 stage, the insect is about 2V inch in length and 

 varies in color from pale yellow to lemon-yellow 

 (Fig. 150). These second-stage nymphs complete their growth 

 in about ten days after hatching ; they then leave the plant and 



Fig. 149. — The 

 onion thrips, 

 first stage 



nymph (X 75). 



