THE CITKUS WHITE FLY: HISTORICAL REVIEW. 11 
The woolly white fly (Aleyrodes howardi Quaintance (PL II, figs. 2, 
4)) was first discovered in this country at Tampa, Fla., by the junior 
author in November, 1909. The insect appears to be of recent intro- 
duction, since the infested area has been under observation at inter- 
vals during the past three and a half years by the several men 
connected with these investigations. 1 
Of the four species known to be destructive to citrus, Aleyrodes 
citri and A. nubifera are included in the investigations herein reported. 
THE CITRUS WHITE FLY. 
(Aleyrodes citri R. & H.) 
HISTORICAL REVIEW. 
Origin. 
The origin of the citrus white fly is by circumstances quite defi- 
nitely indicated to be Asiatic. The present known occurrence of it 
in Japan, China, and India will be referred to under the subject of 
distribution. The list of food plants, showing as it does the natural 
adaptations in this respect, indicates in itself that the fly is not 
native to either North or South America, but to Asia. Moreover, if 
the citrus white fly were a species native to the Gulf coast region of 
North America, or if it had been introduced before 1850, it would 
almost certainly have become a pest worthy of mention by Townend 
Glover in his reports on the orange insects of Florida published in the 
United States Agricultural reports for 1855 and 1858. According 
to these reports orange growing was very extensive in proportion to 
the population and very profitable in spite of the temporary check 
due to the freeze of 1835. The principal orange-growing district in 
Florida was, at the time of the reports of Glover, already mentioned, 
the northeastern section of the State, along the St. Johns River and 
at St. Augustine. Orange growing on a large scale gradually spread to 
the south and southwest, the center of production being correspond- 
ingly moved. To-day citrus fruits are generally grown in all the 
counties of the peninsula of Florida, yet, according to the authors' 
estimates, only about 40 per cent of the orange groves of the State are 
infested by A. citri. 2 These infestations in the different sections are 
almost without exception readily traceable to the ordinary sources 
of dissemination, with all the evidence strongly against the fly having 
been a native species infesting uncultivated food plants. The same 
may be said in regard to the occurrence of the citrus white fly in 
orange-growing regions in Mississippi, Alabama, Louisiana, and Texas. 
1 The Woolly White Fly, a New Enemy of the Florida Orange. Bulletin 64, Part 
VIII, Bureau of Entomology, U. S. Department of Agriculture, 1910. 
2 A. nubifera alone occurs in not more than 5 per cent of the groves. In 15 of the 
40 per cent above mentioned both A. citri and A. nubifera occur. 
