THE PEAR THRIPS AND ITS CONTROL. 58 
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 
larves 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 
