THE PEAR THRIPS. 5 
a way down the center of the cluster, feeding as it goes on the con- 
tiguous sides of the several blossom buds. Normal growth ceases 
immediately. The untouched outer side of each blossom bud 
develops for a time, but the injured inner part becomes brown and 
dies. This causes each flower bud to turn in toward the center, and 
the whole cluster eventually falls. (See Pl. I, fig. 1.) When thus 
injured, most blossoms do not open at all, but if they do thrips are 
able to enter and feed in the more vital flower parts. Only a few 
blossoms survive both periods of injury when thrips are very numer- 
ous. The insects attack blossom and leaf buds alike and, in fact, 
every part that offers new and tender plant tissue. 
Pears suffer mostly during early bud development, and blossoms 
are nearly all dead before the clusters open. 
Cherries present a more resistant growth. There is a decidedly 
sticky secretion on the surface of newly exposed leaves, and often 
wings of thrips stick fast and many are thus trapped. Cherries 
develop so rapidly that when buds once start, blossom clusters are 
able to push out, often almost unharmed, even when many thrips are 
present. These clusters form ideal places for oviposition, and, as will 
be seen later, cherry trees which may be able to resist the early inju- 
ries of feeding will suffer from the effects of ovipositing. 
Thrips have displayed very decided preferences for certain flower 
parts. It has been mentioned that they choose the inner side of the 
almond calyx cup. In prunes they are partial to the tiny blossom 
stems and to the tips of petals and, when blossoms have opened, to 
the stigma and style. This last injury is especially noticeable on 
cherries, where the writer has many times found the stigmas and 
styles blackened as a result of the feeding of thrips, while the rest 
of the blossoms was untouched. 
Injury on leaf buds and on tender foliage is almost as marked as 
when blossoms alone are attacked, although there can be no closely 
drawn line of distinction, because of the close interrelation of leaf and 
blossom buds. Trees that have been ravaged for three or four days 
can not again put forth new leaf buds and assume a natural growth 
for several months, and then they appear sickly for the entire year. 
Often they can not start anew until the thrips have actually left the 
trees, as the insects continue to hinder each new effort which the 
trees may make. 
The pear thrips is known to feed on the following plants, and it is 
probable that this list, extensive as it is, is not complete: Almond, 
apple, apricot (several varieties), cherry, fig, grape, peach (Muir and 
Nicols’ clings preferred), pear (especially Doynne du Comice and 
Bartlett), plum, prune, walnut (English). 
The insect shows a decided preference for certain varieties of 
prunes, pears, and peaches, but of the other fruits all varieties seem 
to be attacked alike. The pear thrips has been colle:ted from the 
