PHYLLOXERA 



373 



and electric light bugs (the last three are aquatic bugs), the 

 cicadas (harvest fly and seventeen-year-locust), and chinch bugs, 

 are all familiar parasites, largely on plant hosts. The Phyllox- 

 era is parasitic on the grape, and merits detailed description. 

 In the spring the first generation of young hatch from eggs which 

 were deposited the preceding fall under the bark of the vine. 

 This generation is wingless and reproduces parthenogenet- 

 ically. Successive generations of similar individuals follow. 



FIG. 236. A tomato worm covered with the cocoons of its parasite, Apanteles, 

 which is also a Hymenopter. (From Folsom.) 



These cause the galls on the leaves and the nodules on the roots, 

 for they also attack the roots underground. In late summer 

 another type appears. These are winged and serve to scatter 

 the species. They lay two kinds of parthenogetic eggs on the 

 underside of the leaves. From the larger eggs there develop 

 females, and from the smaller ones males. These are both 

 destitute of digestive tract. The females, after fertilization, 

 deposit a single egg under the bark of the vine. These eggs re- 

 main over winter and hatch the first generation in the spring. 



