THE INSECT WORLD. 



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distinguished by having only two discoidal veins on the fore- 

 wings. The grape Phylloxera is known by reputation all over 

 the world, and its ravages in European countries have called 

 forth volumes of print. It has been thoroughly studied in our 

 own country by Dr. C. V. Riley, among others, and from his 

 works the following life history is taken. 



The insect winters on the roots of grape, mostly as a young 

 wingless form. This starts growth in spring, rapidly increases 

 in size, and soon commences to lay eggs, the young from which, 

 like their mothers, remain wingless, are also sexless, and also lay 

 eggs ; and so we may have a series of generations of similar 

 creatures, no true sexes becoming developed, no wings appear- 

 ing, and reproduction being entirely through unfertilized eggs. 

 Sometimes, in midsummer, some individuals acquire wings, and 

 thus we get migrating forms, which issue from the ground while 

 yet in the pupa stage, and, as soon as they become winged, fly 

 and spread to other vineyards in the vicinity. Eggs are then 

 laid, usually on the under side of the leaves, from three to eight 

 being the range, while five is perhaps the usual number. They 

 are of two sizes, of which the larger produce females, the others 

 males, and they come from the eggs fully developed and ready 

 to reproduce. These curious creatures have become modified 

 for the one purpose of reproducing their kind, and can neither 

 feed, for the mouth is aborted, nor fly, for they have no wings. 

 After copulation a single egg, almost as large as the insect itself, 

 is developed in the female, and from it hatches a form which is 

 like the type which started the cycle early in the season. Curi- 

 ously enough, it occasionally happens that some of the wingless 

 forms which remain underground also lay eggs of two diflerent 

 sizes, producing males and females, and thus it appears that 

 winged forms are not really necessary to the continuation of the 

 species. Quite usually wingless individuals abandon the roots 

 and crawl up the stems to the leaves, where they form the galls, 

 which are the most prominent external mdications that a vine 

 is infested. I have seen vineyards in New York and New Jersey 

 in which almost every leaf showed these galls, yet withal no real 

 injury had been done. In other words, most of the native 

 American vines are able to sustain the attack of the species. 

 This is not true of the vines in Europe, where this insect has 



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