100 THE AQUARIUM. 



natator—^\\ou\d be captured ; they are quite inoffensive. It 

 should be borne in mind that all these beetles are not entirely 

 aquatic ; consequently, if kept in an uncovered aquarium, are apt 

 in summer to take flight during the night. They should be kept 

 in a vessel provided with a cover. 



A very common but curious insect is the water scorpion, 

 Nepacwereus, a member of the Hefnipiera. Although far from 

 being a vegetarian, it may be safely kept in an aquarium with 

 other things if occasionally fed with flies. These it catches with 

 its first pair of legs, and thrusts it upon its sharp-pointed snout, 

 through which it extracts their blood. Its appearance resembles 

 a small flattened leaf, grey above, and often reddish beneath, with 

 a long pin-like tail. It scrambles about in the water upon the 

 weeds or rests on the surface with its fore-legs extended on the 

 watch for flies. There is another water-scorpion, Nepa lineatiis, 

 but much rarer than this, which is a very close approach to the 

 exotic stick insect in appearance ; in fact, when drawn from the 

 water and feigning death, it is difficult to recognise a living insect. 

 This is similar to the common water-scorpion in its habits, and in 

 attitude recalls the well-known ' praying mantis ' while laying in 

 wait for flies. Both these insects are very subject to the attacks 

 of parasitic acari, which will seem adhering to them like minia- 

 ture sheep-ticks. 



No aquarium should be without a couple of water-boatmen, 

 Notonecta glauca. They may be known at once by their curious 

 action when swimming on the back, recalling an out-rigged 

 scuUing-boat. These, too, are not above staying their stomachs 

 with their fellow captives, but will not do so if fed on flies, which 

 they will even seize from the fingers, clasping their prey as though 

 nursing it, and keeping it beneath the surface until it is drowned. 

 There are three common species — one large, and with hard, 

 coloured wing cases ; the others flatter, and with elytra reticulated, 

 Conixa striata and affinis. Unfortunately, the first preys greedily 

 upon the latter two, so that they cannot be kept together for long. 



Among larvae we have a wide selection of curious forms, which 

 may be successfully reared, but in collecting we should be 

 cautious not to include any with large sickle-shaped or knife-like 

 jaws ; such are certain to be carnivorous and predatory. A little 



