Economic entomology for the farmer Economic entomology for the farmer and the fruit grower, and for use as a text-book in agricultural schools and colleges; economicentomolo00smit Year: 1906 THE INSECT WORLD. 377 out devouring any part of its vegetable envelope, changes to a pupa, and emerges from the gall, leaving it intact, except for the hole through which it emerged. It seems, therefore, as if certain abnormal plant ex- udations secreted in the ^^^- 433- gall form the actual food of the larva, and it is a curious and interesting fact that the same species in- variably produces in the same
Economic entomology for the farmer Economic entomology for the farmer and the fruit grower, and for use as a text-book in agricultural schools and colleges; economicentomolo00smit Year: 1906 THE INSECT WORLD. 377 out devouring any part of its vegetable envelope, changes to a pupa, and emerges from the gall, leaving it intact, except for the hole through which it emerged. It seems, therefore, as if certain abnormal plant ex- udations secreted in the ^^^- 433- gall form the actual food of the larva, and it is a curious and interesting fact that the same species in- variably produces in the same place the same kind of gall. In other words, the appearance of the gall is an unfailing index for An oak gaii-fly. the special student to the species that made it. Many interesting problems are connected with the study of these gall-flies ; for instance, in some species both sexes are present early in the season, but in the second or midsummer brood females alone make their appearance. The Fig. 434.
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