THE PEAR THRIPS AND ITS CONTROL. 55 
The period of blossoming for similar varieties in Contra Costa 
County is about the same as that in the Santa Clara Valley, while the 
orchards in the Vaca and Suisun valleys and along the Sacramento 
River may be a very few days earlier. 
INJURY TO TREES BY OVIPOSITION. 
The adult female is equipped with a pointed and curved, sawlike 
ovipositor (fig. 13), by means of which deep cuts are made, into which 
the eggs are placed well down into the tissues of the plants, mostly 
in the stems of blossoms or leaves or into the leaf tissue. A single 
incision is minute and in itself does little harm, as the wound soon 
heals over, but the tiny stems of the blossoms or of newly setting 
fruits and the leaf petioles are unfortunately preferred by the insect 
for ovipositing situations, so that many incisions are often cut into a 
single stem, which, becoming greatly 
weakened, turns yellow and the fruit 
falls. This injury becomes very notice- 
able at times on the prune and cherry 
and is undoubtedly the cause of much 
dropping of immature fruit. 
INJURY BY LARV&. 
ra 
Thrips larve are wingless, never of 
their own accord traveling from the : 
host plant on which they are born, and pe peRutrant ia of ys bet 
usually do not move far from the im- acne Muchenlarged. (Author’sillus- 
mediate locality where they have issued 
from the egg. They seek some sheltered place within a cluster of 
leaves, in blossoms, or under the protection of the drying calices of 
such fruits as prunes or cherries. Larve are found mostly during the 
last of March and in April and their injury is distinctly on leaves and 
fruits and not in opening buds. To them must be attributed almost 
all the scabbing on prunes (Pl. VI, figs. 2, 3), some silvering on apri- 
cots and peaches, and most of the deformed, ragged, and partly dead 
leaves. This injury to the foliage greatly stunts and weakens a tree 
if it is repeated during several successive years. 
ey é 
4 
SEASONAL HISTORY AND HABITS. 
APPEARANCE OF ADULTS FROM SOIL IN SPRING. 
The following table shows clearly just when the first adult thrips 
are leaving the ground, when in maximum numbers, and when the 
last individuals are appearing. The figures here represent the total 
number of thrips collected from four cages from each of four orchards 
30490°—Bull. 80—12——5 
