Identifier: introductiontozo00dave Title: Introduction to zoology; a guide to the study of animals, for the use of secondary schools; Year: 1900 (1900s) Authors: Davenport, Charles Benedict, 1866-1944 Davenport, Gertrude Anna Crotty, 1866- Subjects: Zoology Publisher: New York, Macmillan company London, Macmillian and co., ltd. Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library

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Text Appearing Before Image: of the passageways, and a fungus isgrown upon them which serves the ants as food. The leaves areprobably stored to provide this fungus food. The parasitic Hymenoptera have the habit either of lay-ing eggs in the body of another insect, — one of the plant-lice, a caterpillar, or other species, — or else they lay theireggs in the nest of some species of insect so that the larvacan make its own way into the host (Figs. 36-38). Thelong, tail-like ovipositors of the female ichneumon are, in some cases, used to drillholes into trees occupiedby insect burrows so thather eggs can be laidtherein. These parasiticspecies are invaluable toagriculture in keepingdown injurious insects. The gall-wasps, popu-larly not distinguishedfrom the strict gall-flies,are familiar to us fromthei;1 works. They layeggs in various kinds ofplants, especially in oaks and members of the rose family.An excessive growth of the plant tissue, called a gall, iscaused either by a poison dropped into the plant with the

Text Appearing After Image: FK;. -37. — Cocoons of Microgaster, a para-sitic hymenopter, on a sphinx larva.Photo, from the living object by V. H. L. THE BUTTERFLY AND ITS ALLIES 39 egg, or by the irritation of the developing embryo.1 Thegalls of gall-wasps are often more or less spherical masses

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