THE PEAE THRIPS AND ITS CONTROL. 53 



the period of the early opening of buds, of blossoming, and of the 

 unfolding of leaves and the setting of fruit. They come to the trees 

 ravenously hungry after a long fast of ten or eleven months in the 

 ground, and they force an entrance as soon as possible into the first 

 opening buds. Their habit of getting inside immediately has led 

 many orchardists to believe that they in some mysterious way gain 

 entrance into the buds before these are opened. This is not the case, 

 as the insects never enter until after the buds are swollen and partly 

 or wholly opened at the tips. They do not feed on the tough tissues 

 of the bark or on the outer bud scales, but wait until they can get 

 inside. When thrips are very numerous these early buds either 

 never open at all or form only weak blossoms, which present the 

 appearance of having been burned (PI. V, fig. 1). Thrips will usually 

 migrate in search of new food plants after the blossoms are thus com- 

 pletely destroyed, which explains, in part at least, why they may 

 temporarily disappear from a given orchard or part of an orchard, 

 where perhaps a few days previous they had been numerous enough 

 to destroy the entire crop. When thrips are less numerous the 

 injury is accumulative, but it may finally prove as serious as when 

 many more thrips are present. A few individuals may continue to 

 feed within clusters for days or even weeks. The growth of the tree 

 is then retarded and its blossoms and leaves become weak and de- 

 formed. Trees may produce a heavy bloom, even where many thrips 

 are present, but the blossoms and leaf stems will be scarred, weak- 

 ened, and abnormally short and the fruit does not set. This is 

 especially true of prunes. A few adult individuals may feed in a 

 cluster of pear blossoms, and although the buds drip with exuding 

 sap and are moldy, many if not all of these pears may set and there 

 may follow a heavy crop of fruit, but always in such cases the fruit 

 is ill shaped and badly scabbed. The scabbing on pears (PL V) is 

 accomplished almost entirely by adults which feed within the clusters 

 of buds, while scabbing of prunes (PL VI) is done almost entirely by 

 larvae which feed on the fruits under protection of the old calices 

 before these are sloughed off. 



Injury by adults in almonds, apricots, and peaches is not serious 

 unless very many individuals are present. These trees bloom rather 

 early, and since each blossom comes singly in a bud, there is offered 

 almost no opportunity for the thrips to get inside until the blossom 

 itself is well opened, whereupon the thrips feed mostly on the nectar 

 glands inside the calyx. This part of the blossom can accommodate 

 quite a few thrips without receiving serious injury, and also the insect 

 is diverted from feeding on the more vital parts. There follows 

 serious injury on these fruits only when many waiting individuals 

 enter the buds and feed on the outside of the little calyx cups and the 



