The White Flies or Aleyrodids 



body may be more or less covered by a secretion of wax, 

 but the most distinctive character is the presence of an opening 

 on the dorsum of the last abdominal segment which is known as 

 the vasiform orifice. In the adults the antennae are seven- 

 jointed, and the eyes are usually somewhat constricted near the 

 middle, and may be even completely divided. The wings when 

 at rest are nearly horizontal, and are broad and well rounded. 

 The wings may be unspotted, or variously spotted or banded. 

 The Aleyrodidae do not constitute a large group, and but two 

 genera and not more than 1 50 species are known. Of these both 

 genera (Aleyrodes and Aleyrodicus) are known in the United 

 States, and rather more than fifty species occur within our 

 geographic borders. Doubtless many of these are imported, 

 since they occur more commonly upon greenhouse plants than 

 upon wild indigenous plants. They are found upon both herb- 

 aceous plants and upon forest trees. They are very seldom 

 serious enemies to vegetation, although the species occurring com- 

 monly upon the orange does considerable damage, which arises not 

 alone from the actual loss of sap and consequent withering of the 

 leaves from the sucking of the insect, but also from the profuse 

 quantity of smut fungus, the spores of which find their nidi in the 

 honey dew secreted by the insects. Their natural enemies are 

 practically the same as those of the scale insects, but the very 

 minute Hymenopterous parasites of the family Mymaridas seem to 

 be their specific internal parasites. In fact, they are too small to 

 harbor any other true internal parasites except the members of 

 this family, which, as a matter of fact, includes the smallest true 

 insects known. 



Typical Life History of a White Fly 



(Aleyrodes citri, Riley & Howard.^ 



This species, which is the only form of any great economic 

 importance in the group and the one to which we have just re- 

 ferred, occurs abundantly in some of the orange groves in Florida 

 and in northern greenhouses and made .'ts appearance about 1890 

 in the orange groves of Louisiana. It is not known whether it 

 is an indigenous or imported species. It will probably be found 



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