THE CITRUS THRIPS. 3 
Although the insect occurs in injurious numbers in Arizona, thus far 
it has been taken only in the Salt River Valley near Phoenix and 
Mesa (fig. 2). Dr. A. W. Morrill informed the writer by letter that 
he thought he detected traces of thrips injury in an orange grove near 
Yuma, but specimens have not been taken there. 
POSSIBILITY OF ITS OCCURRENCE ELSEWHERE. 
No verified reports of the occurrence of the citrus thrips in States 
or countries other than the foregoing have been made, although it 
is said to occur at Hermosillo, Sonora, Mexico. There are various 
reports of thrips injuring citrus 
fruits, the species concerned being 
often in doubt. Thus, Tower 1 
states that certain scars found on 
oranges in Porto Rico probably 
are caused by thrips which were 
present in the trees in great num- 
bers, but the identity of the thrips 
is not given. Rolfs, Fawcett, and 
Floyd 2 describe injury to oranges 
in Florida by a thrips which ap- 
pears to be FranMiniella (Euthrips ) 
tritici Fitch, if indeed the injury 
illustrated by them is caused by 
thrips. The citrus thrips does not 
occur in southern Louisiana, and 
doubtless could not thrive there 
because of the high humidity and 
heavy rainfall, and for the same reason probably does not occur in 
Florida. 
NATURE AND EXTENT OF INJURY. 
Fig. 2. — Map showing present-known dis- 
tribution of the citrus thrips in Ari- 
zona. (Original.) 
The citrus thrips obtains its food by puncturing the tissues and 
draining the contents of the cells, causing the cell walls to collapse. 
Growth expansion of the surrounding living cells leaves the punc- 
tured and dead areas sunken and distorted. The very characteristic 
scabbing of the fruit is caused by the dead and dry cell walls being 
forced outward by the growing cells beneath, the resultant scabs 
often covering a large portion of the rind. The various rings, 
streaks, splashes, and other patterns in the tissues result from the 
almost incessant movement of the thrips as they feed (PI. I). The 
1 Tower, W. V. Insects injurious to citrus fruits and methods for combating tbem. 
Porto Rico Agr. Exp. Sta. Bui. No. 10, p. 20. 1911. 
2 Rolfs, P. H., Fawcett, H. S., and Floyd, B. F. Diseases of citrus fruits. Fla. Agr. 
Exp. Sta. Bui. 108, p. 32-33. 1911. 
