THE ORANGE THEIPS. 3 
Blood. St. Michael, Homosassa, and seedlings) ; Citrus nobilis (Sat- 
suma and tangerines) ; Citrus decmnana (grapefruit) ; Citrus medica 
var. limon (lemon) ; Citrus medica var. acida (lime, varieties of) ; 
and Citrus japonica (kumquat). 
The following miscellaneous plants are infested : Punica gramatum 
(pomegranate) ; Vitis vinifera (European grape, varieties of) ; 
Schinus molle (California pepper tree); "umbrella tree;" Pyrus 
communis (pear) ; Prunus armeniaca (apricot) ; Prunus persica 
(peach) ; Prunus domestica (European plum, varieties of) ; Salix sp. 
(willow) ; Rumex sp. (dock) ; Portulaca oleracea (purslane) ; Olea 
europea (olive) ; Rubus idceus (reel raspberry) ; Rosa sp. (rose) ; 
Solanum sp. 
CHARACTER AND EXTENT OF INJURY. 
Injury to citrus trees and fruit is caused directly by the feeding 
of both adults and larva? upon the surface of the parts attacked. 
This feeding may be on the young fruit (Plate I, figs. 1, 2) , the nearly 
mature fruit (Plate II), or the new, tender foliage (Plate III), and 
generally takes place on all of these. The injury to foliage is gen- 
erally on young leaves, but may also occur on the axillary buds. 
The manner of feeding of both the adult and larva of the thrips is 
identical, and consists in piercing the plant tissues with the sharp 
mouthparts with which both stages are equipped and then rasping 
the wound by a " rooting " motion of the head. The vegetable juices 
thus liberated from the plant cells are sucked into the alimentary 
canal of the insect. The characteristic marking or scabbing of the 
fruit, so noticeable at picking time, is started when the fruit is very 
small — just after the petals have fallen from the blossoms. This 
scabbed area is small at first, but as the fruit grows and the thrips 
continue to feed the markings deepen and at the same time the area 
of injury is enlarged. The continued feeding of a large number of 
thrips results in the scabbing of nearly the entire ^surf ace of the fruit. 
Often the marking is so large and deep over a portion of the orange 
that it causes the fruit to be misshapen and aborted. Frequently the 
entire surface is scarred while the fruit is still small, with the result 
that it ceases to grow and falls from the tree. 
Orange trees in the Tulare County citrus belt make about four dis- 
tinct growths a year, and it is on this tender foliage that the orange 
thrips multiply in greatest numbers. The feeding of large numbers 
of these little insects causes the young leaves to curl and become dis- 
torted and the whole growth to present a sickly appearance. Young 
trees are often held back a year or more in growth by the prompt 
destruction of the terminal buds soon after these make their 
appearance. 
