THE CAMPHOR THRIPS. 17 
thrips which escaped from a jar flew to a window about 3 feet away. 
When disturbed on the trees the adults will crawl around the limb 
or enter some lesion rather than fly away. 
The natural distribution of the species also tends to prove that 
flight is of little importance as a means of spreading the insert-. 
Sometimes in borders of camphor trees along a street some trees are 
infested while others are entirely free. Camphor trees have remained 
free from thrips for several years within a few rods of an infested 
hedge. Trees planted on farms often remain free when the thrips occur 
on other farms less than a mile away. On the other hand, practi- 
cally all the trees in the fields of the camphor plantations where 
regular cultivation is practiced are infested. This would indicate 
that the thrips are spread by workmen or teams much more than by 
flight. Probably the greatest factor in distributing the insects over 
the State has been the movement of infested trees and nursery stock. 
FEEDING HABITS. 
All portions of the tree are subject to attack by the thrips except 
the roots. During the periods of growth the new buds seem to be 
the favorite food, but later the thrips attack the young shoots and 
limbs and also work in the cracks and lesions of the older limbs. 
The greatest injury to the trees probably results from the work of 
the thrips in the buds. Larvae and adults both feed about the bud 
scales and cause the buds to turn black and die. The entire new 
flush of growth on a tree is sometimes killed in this way. This type 
of injury is illustrated in Plate II. The tender young shoots are 
blackened also in spots by the punctures of the insects, as shown in 
Plate III. One thrips is capable of blackening a considerable area 
of bark in a single day by its feeding punctures. This work is done 
mostly by the larvse. Although the adults are often seen running 
about over the leaves and limbs and cause some of the injury, they 
do not feed so much in exposed places as they do in the bark lesions. 
As the limbs grow older these blackened spots become dead areas over 
which the bark cracks (PI. IV, A). Deep cracks or lesions result 
later, the injury often being aggravated by further feeding of the 
thrips on the cambium layer of the wood inside these lesions. At 
times this advanced stage of injury even deforms the limbs (PL V) . 
When once the insects are inside of the limb they will often tunnel 
back for several inches by hollowing out the pith of the stem. In 
these secluded places the pupa stages are passed, and here also the 
larvae and adults pass periods of rainy or other unfavorable weather, 
and even hibernate in some cases. 
The camphor thrips, however, should not be charged with all the 
injury done to the buds. Fields of camphor trees have been ob- 
served which showed a considerable number of blackened buds and 
dead shoots caused by Heilipus apiatus Oliv. This large and con- 
spicuous black and white weevil gouges out the sides of the stems 
near the tips. The entire new growth on the limb then dries up and 
turns black. The effect of this injury on a field of young camphor 
trees is similar to that caused by the thrips. 
