FAMILY ALEYRODID.E 129 



the use of tobacco extract or 7 per cent, kerosene emulsion 

 may be used. 



In another group of aphids we have the gall-makhig 

 pemphiginse which cause conspicuous deformations upon the 

 leaves of many different plants. Some of the more con- 

 spicuous ones are the vagabond gall on cottonwood, and the 

 poplar leaf galls. 



Grape Phylloxera. — The Grape Phylloxera is one of the 

 very destructive insects of the grape-vine and is known over 

 a wide territory, having been carried from America to Europe, 

 where it caused a great deal of destruction to the vineyards, 

 especially in southern France. It affects the roots of the 

 vines and occurs on these during autumn, winter and early 

 spring, but during midsummer migrates to the leaves, caus- 

 ing the production of leaf galls, so conspicuous at that time. 

 By the time these galls mature or the leaves ripen the insect 

 migrates to the roots. The use of bisulphide of carbon 

 injected into the soil is the most available remedy, but there 

 is so much difference in the resistance of different varieties 

 of grape that the cultivation of thick-leaved kinds is con- 

 sidered advantageous. Where flooding is practicable, the 

 submergence of the insects for a period of two or three days 

 is effective. 



Numerous species of phylloxera occur on the leaves of 

 hickory, walnut, and other trees, but for the most part are 

 not considered of especial economic importance. 



Family Aleyrodidse — The next family in the series is the 

 AleyrodidoB. These are forms which have a mealy covering 

 on the wings and have the eyes divided, each compound 

 eye being divided into two, and the antennae being located 

 within the division of the eye. The adults are very similar 

 but the larvae and nymphs which form scale-like bodies on 

 trees have very distinct characteristics so that the species 

 are to be distinguished by the study of these stages rather 

 than of the adults. They resemble somewhat the scale in- 

 sects, but the adult characteristics are quite different. The 

 scales are quite distincti^'e. In many cases there is a fringe 

 of white, waxy material which seems to act as an attach- 



