THE INSECT AQUARIUM. 



33 



{Notonecta glaticd) is one of the most interesting, and for 

 oddity of form the flat Water Scorpion {Nepa cinerea), 

 the strawlike Water Measurer {Ranatra linearis) and the 

 active Gerris. In addition there are two other species of 

 Diptera, — the Hoverer flies and the Crane flies (Daddy 

 Long-legs). The larva of the Hoverer fly {Eristalis) is 

 known as the Rat-tailed Maggot, and inhabits the mud 

 of ponds and water-butts. The Crane fly larva is known 

 as the " blood-worm," and is a favourite food for fish. 



In the insect aquarium may also be included several 

 species of minute Crustaceans, — the Water-fleas. Under 

 this name are included three species at least, — Daphnia, 

 Cypris, and Cyclops. They 

 are very minute creatures, 

 and, like their larger rela- 

 tives, cased in plates of mail. 

 They are very active and 

 equally prolific. In fact, it Water-Fieas. 



has been estimated that the progeny of a single female 

 Daphnia may amount during her lifetime to the enor- 

 mous number of four billions and a-half, which would 

 weigh in the aggregate nearly eight tons. It is this as- 

 tonishing rate of increase that renders them useful 

 occupants of the fish-tank, for they form no inconsider- 

 able portion of the fishes' food. 



It must, of course, be understood that an abundant 

 supply of vegetation is required in the insect tank, and 

 it will be necessary to treat the inmates to a dead fish 

 occasionally. 



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