CHAPTER II. 



ENTOMOPHAGA, OR ICHNEUMONS AND GALL FLIES. 



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The large group of Hymenoptera which comes next in order is 

 almost wholly parasitic in its character — most of the species 

 feeding while in the larval state, on the bodies of other insects. 

 There are, however, many which obtain their subsistence from 

 plants, which are wounded by the mother insect and are deve- 

 loped into the curious growths which are popularly called galls. 

 The arrangement of these insects is singularly intricate, and in 

 many points still affords objects of controversy to systematic 

 entomologists. We will therefore content ourselves with a 

 general rather than a detailed view of those remarkable insects, 

 and place them under the comprehensive name of Ichneumonidse. 



Many of these insects deposit their eggs within the bodies of 

 larvae that are buried either in wood or in the earth. Anyone 

 would think that the grub of a wood-boring beetle, or the cater- 

 pillar of a wood-boring moth, would be quite safe from any 

 external enemies, so long as it remained concealed within the 

 timber. The Ichneumon Flies, however, are able, by some mys- 

 terious instinct, not only to discover the exact locality of the 

 hidden larva, but in spite of all obstacles to deposit their eggs 

 within it. Slight and delicate as is the ovipositor in many 

 species, the actual borer being scarcely thicker than a hair, it 

 can make its way even through thick wood, and thus act as 

 a channel through which the egg is conveyed to its destination. 

 The movement by which this operation is conducted is exactly 

 that which is employed by a carpenter when using a brad-awl. 



Without going further into details, we will proceed to the 

 examination of the insects which have been selected as typical 

 examples of this vast group. 



