10 



DECIDUOUS FRUIT i;^SECTS AND INSECTICIDES. 



nymphs from the ground early in ]\Iay, but it is difficult to explain 

 their presence there so early in the spring. It hardly seems possible 

 that these were the still immature forms of the previous year, for by 

 this time all adult thrips had left the trees. These nymphs were 

 taken along with the larva^, which had just entered the ground, and 

 it might seem that they were hurrying through to produce a second 

 generation; but to the writer's certain knowledge adults of a second 

 generation did not appear on the trees. The nymph is active at all 

 times. Wings develop from mere buds to long sacs which project 

 backward along the sides of the body, and eventually reach beyond 

 the tip of the abdomen. 



THE ADULT. 



The adult thrips (fig. 6) remain in the pupal chamber for days, 

 and it may even be weeks before they issue forth to take up active 



life. How individual thrips force their 

 vx'ay through the several inches of earth 

 which lies above them is still a question. 



The}^ come out, it 

 seems, only after 

 the ground has 

 been thoroughly 

 soft en e d by 

 rains, and it is 

 evident, too, that 

 they d e p e n d 

 largely on the 

 n a t u r a 1 open- 

 ings. They can 

 not possibly use the backwardly bent mouth 

 cone as a means of boring or biting their way 

 out. They have scA^eral groups of spines and 

 certain angular edges on the sides of the ab- 

 dominal segments, however, which might be used 

 in forcing a way through the soft soil. They 

 also possess roughened, scoop-like structures — 

 parts of the chitinous, hoof-like shell of the 

 feet — which undoubtedly are used for digging. 

 Adult thrips appeared in alarming numbers 

 in many Santa Clara Valley orchards in 1904, about February 24; 

 in 1905 several days later, and in 1906 about March 1. They appear 

 on the trees by millions and, it seems, all at about the same time. 

 They feed and oviposit most actively during March and April, and 

 by May 1 almost all have disappeared. No male individuals of the 

 pear thrips have twer been collected ; all have been females. 



Fig. ().— The pear tin ips ( /■-'«- 



Ihrips pyri): athilt. Much 

 ( nlarged (original). 



