AND OTHER IXJLRIOUS INSECTS OF IQC/ AND I908. I4I 



THE GRAPE PHYLLOXERA. 



Plivllo.vcra vasfatri.v Planch 



--■"=^A_>-~-m .^r^^UDCT^ 



Fig. 71. Grape Phylloxera, a, leaf with galls; b, sections of gall showing mother 

 louse with young clustered about her; c, egg; d, larva; e. adult female; /, same from 

 side; — a, natural size, rest much enlarged. After Marlatt, Bur. Ent., U. S. D. A. 



vSpecimens of both ciihivated and wild grape leaves infested with 

 this insect were sent this department during the summer of 1908. The 

 affected leaves are characterized by little wart-like growths on their 

 surface. There is, however, another form distinct from the leaf form, 

 which occurs on the roots, where it works unseen, and in cases of bad 

 infestation is sure to kill the vine. It is the root form which is to be 

 dreaded, not the leaf form. The former makes characteristic swellings 

 or galls on the smaller roots, extending its work to the larger roots, 

 finally killing the same. 



Serious infestation of the roots is indicated above the ground by 

 the sickly appearance of the vine, a yellowing of the leaves, lack of 

 growth, etc. It is claimed that when the leaf form is very abundant 

 the root form is not in injurious numbers on the same vine, and vice 

 versa, an abundance of the root form is not accompanied by an 

 abundance of the leaf form. 



The reproduction of this louse, for it is a form of plant louse, re- 

 sembles in a general way that of other aphids ; sexual females in the 

 fall laying eggs which winter over, and give rise to the stem mother 

 in the spring. The young louse, upon hatching, feeds upon the leaf, 

 its attack causing a depression in the leaf, the insect finallv becoming 



