INSECTS INJURIOUS TO THE GRAPE 



435 



dered mustard, according to Quayle. He states that "the newly 

 hatched insect is fairly active, and at first moves from place to 

 place on the roots, but finally, when it reaches the egg-laying 

 stage, inserts its sucking-tube into the root and remains fixed." 

 During the late summer and early fall some of the root-lice develop 

 into winged females which escape through cracks in the soil and 

 fly to neighboring vines. They lay from two to four eggs beneath 

 the loose bark on the old wood and soon die. "The eggs are of 

 two sizes, the smaller 

 and fewer in number 

 yielding males in nine 

 or ten days, and the 

 larger the females of 

 the only sexed genera- 

 tion in the whole life 

 round of the insect. 

 In this last and sexed 

 stage the mouth-parts 

 of both sexes are rudi- 

 mentary, and no food 

 at all is taken. The 

 insect is very minute 

 and resembles the 



FIG. 365. Grapevine phylloxera: a, root galls; 

 b, enlargement of same showing disposition 

 of lice; c, root-gall louse much enlarged. 

 (After Marlatt, U. S. Dept. Agr.) 



newly hatched louse of either the gall or root form. After fertili- 

 zation the single egg of the larva-like female rapidly increases 

 in size until it fills the entire body of the mother and is laid within 

 three or four days, bringing us back to the starting point." * 

 The phylloxera has been distributed over the world by infested 

 rooted plants or cuttings bearing winter eggs, and it spreads 

 locally by means of the winged females, by the escape of the 

 young root-lice through cracks of the soil and their migration 

 to neighboring plants, or by bits of infested roots being spread 

 in cultivation, and by the leaf-gall lice being spread to other 

 plants by the wind or by being carried by birds or insects. 



Control. The principal means of control lies in the use of 

 resistant vines. These may be varieties which have proven 

 successful in the eastern United States, where the insect is native, 

 or more commonly the stocks of grapes from the Eastern States 



* Quotations from Marlatt, 1. c. 



