Page:The Book of the Aquarium and Water Cabinet.djvu/153

Rh The Notanecta, or Boat-fly, is a rapacious creature, that spends much of its time lying in wait for prey, but which exhibits immense activity when it captures its booty, darting down with it, and holding it firmly by the fore-legs, which are formed as claws. It is ingeniously adapted for the predaceous aquatic life it leads; the general form is well adapted for propulsion through water, and the hinder legs have an oar-like form, and are fringed with bristles along the edge, by which their striking surface is much increased. The boat-fly is an artistic swimmer; it varies its motions considerably, and delights in swimming on its back, a feat in which it is aided by its eyes being so placed as to enable it to see both above and below, and thus gain early intelligence of danger, or of the approach of its prey. Owing to their liveliness and voracity, they afford much interest when domesticated, and should be treated as directed for Dytiscus.

The Water Scorpion is a good representative of the Nepidæ, and has the distinguishing features of its tribe very strongly marked. The Water Scorpion is a very common inhabitant of our brooks, and its singular form quickly arrests the eye of the sportsman when turning over the contents of the drag-net. N. neptunia and N. cinerea are, perhaps, the most common; and either of these is an admirable object for the microscope. The water-scorpion is the victim of the parasitic water-mite (Hydrachna abstergens), which inserts its egg in the body of the Nepa, and thus compels it to support the young of its worst enemy, a task which it performs at the