THE PEAR THRIPS. 



the plant epidermis with the stylets, then, movinji; the cone tip back- 

 ward and forward, it enlarges the opening and lacerates the plant 

 tissue by means of the barbed snout. It then pushes the tip of the 

 mouth cone into the puncture thus made and sucks in the plant 

 juices. LarviF feed in a similar way, having similarly constructed 

 mouth-parts. 



RELATION OF THE BUDDING AND BLOSSOMING OF TREES TO THE FEED- 

 ING HABITS OF THRIPS. 



The dark-brown adult thrips arrive on the trees in late February 

 and early March, the period of early opening buds and first blossoms ; 

 they are common in March and April, the two months of bloom and 

 early leaf, and all are gone from the trees 

 by the middle of May. Only a few adults 

 can be found after the 1st of May, and most 

 larvae have reached full growth by tliis time 

 and have gone into the ground. Thus it is 

 that the active feeding stages of the thrips 

 coincide with the budding, blooming, and 

 early leaf periods of the host trees. 



The difference in bud formation and pro- 

 gress of development of various deciduous 

 trees influence to a large extent the man- 

 ner of injury which thrips inflict. Trees may 

 be divided for the sake of convenience, in re- 

 gard to the bud structure, into two groups, 

 namely: (1) Those in which a single fruit bud 

 produces one blossom, such as the almond, 

 apricot, and peach; and (2) those in which a single fruit bud opens 

 out to form a cluster of blossoms which later produces a cluster of 

 fruits, as the prune, cherry, pear, and apple. 



The relative blooming periods of the several varieties of fruit on 

 which thrips inflict injury, as found \u the Santa Clara A'allc}^, may 

 be noted as follows: 



Group 1: Almonds, late in Fcliniary; ai>iicots and jicachcs, early in Manli. 

 Gronj) 2: Prunes, middle and last of March; clierries and pears, early in April. 



These periods vary from year to year and the varieties of each 

 fruit also vary to a large degree, but the general order of blooming is 

 suggestive. Opening buds precede full bloom by eight or ten days. 



The almond, of the first group, presents an interesting study of 

 the feeding habits of thrips. The bud development occurs dur- 

 ing early February, early blossoms from February 5 to 16, and 

 full bloom from February 9 to 20 and later. Thrips aj)pear about 

 February 25 or March 1, and it is evident that almond blossoms are 



Fig. 1. — The pear thrips (,Eulhrip.<i 

 pyri): head and prothoraxfrom 

 side, to sliow mouth-parts. 

 Much enlarged (original). 



