70 MANUAL OF VEGETABLE-GARDEN INSECTS 



or white, dry up and die. In some eases the plants may ])c 

 entirely killed. The bean thri})s has been most injurious in 

 California but also oecurs in Idaho, Utah, Nevada, Arizona and 

 Tennessee. It is not eonfined to the bean but attacks many 

 other plants, including beet, cabbage, lettuce, radish, potato, 

 tomato, i)ea, i)ear, alfalfa and cotton. Among weeds, its 

 favorite food plants are spiny lettuce, sow thistle and wild 

 heliotrope. 



The bean thrips hibernates in the adult condition on the 

 underside of the leaves of nasturtium, beet, wild heliotrope 

 and many other plants. It is also found in dried leaves 

 and under rubbish. In the warmer parts of its range, the insect 

 is active throughout the greater part of the year, feeding being 

 interrupted only for a short time during cool spells. On emerg- 

 ing from hibernation, the adults immediately seek their food 

 plants and after feeding for a short time the female deposits 

 her minute translucent white, bean-shaped eggs, about yw^ 

 inch in length in the tissue of the leaves, in the veins and even 

 in the stems of beans. The eggs hatch in thirteen to eighteen 

 days. The newly hatched nymph is about ^-^ inch in length 

 and uniform translucent white in color with the eyes reddish. 

 In the second stage, the nymph is about -^ inch in length 

 with the head and prothorax light yellow and with the re- 

 mainder of the body translucent white and stained on the side 

 with crimson. During the first two stages, the nymphs feed 

 on the leaves in the same way as the adults. AYhen full-grown, 

 they desert the plants and hide in rubbish and in cracks in the 

 ground and there molt. In the third stage, the nymph or so- 

 called prepupa is slightly smaller than in the preceding stage 

 and the wing-pads are well developed. The insect does not 

 feed in this stage but in from one to six days, depending on the 

 season, it molts again. In the fourth stage or so-called pupa, 

 the nymph is -^ inch in length, yellow or orange in color, 

 marked with crimson on the sides and across the abdomen and 



