together with a great quantity of other forms of pond life, and placed them all in glass aquaria to study their feeding habits. The bugs seemed to feed most voraciously upon the larvæ or Fig. 5.—Undulating Backswimmer. nymphs of dragon flies. These were captured continually, and their juices greedily sucked out. The next most abundant victim was the common undulating backswimmer (Notonecta undulata) shown in Fig. 5. In one aquarium, in which a large amount of pond material, including half a dozen zaithas, had been placed, four of the latter were in sight at one time, each with one of these backswimmers grasped in its front legs and the beak inserted in the body.

Small fresh-water snails occasionally contribute to the diet of this insatiable creature, and young mayflies are also commonly eaten. Flying insects which fall upon the surface of the water are sometimes caught and killed.

The giant water bugs are typical examples of the true bugs. They belong to the group called by naturalists Heteroptera, the members of which are characterized by having two pairs of wings, the front pair being thickened at the base and thin at the tip, and mouth parts fitted for sucking rather than for biting. During their development they do not undergo so complete a series of changes as do the caterpillars, which transform into butterflies, but grow more like the grasshoppers, the young resembling the adults in general appearance but having no wings. These bugs can be dipped out of ponds and ditches almost anywhere by means of a net, and are easily kept in aquariums, where they form interesting objects for study.