OR, THE HOME-CULTURE OF FRESH-WATER PLANTS. 
Whirligigs ( Gyrinidce ), so called from their whirling 
movements on the surface of the water, where their 
shining coats of bright bronze have a glittering 
appearance in the early days of spring. There are 
also the Water Boatmen ( Notonecta ) and the Water 
Scorpion (Nepa), well worthy of a place in the 
tank. 
There are also the Caddis Worms of different 
kinds, which form interesting objects, clothed in their 
portable house of little sticks and stones (see Plate 
III.), which protects them from the attacks of fish 
or other insects. Thev are the larva stages of 
e/ O 
various species of Phryganea. 
One of the most interesting creatures in a tank 
is the Diving Spider (Argyroneta aquatica ), which, 
however, should not he placed with fish or voracious 
beetles, or he would soon disappear. The trans¬ 
parent membrane which surrounds the body of the 
Water Spider, and enables him to swim, gives him 
the appearance, when in motion, of a globule of 
quicksilver—an appearance which has rendered him 
a great favourite with keepers of Aquaria. There 
are other species of Water Spiders, but living upon 
the surface of the water, and not having the power 
of diving, they are not so attractive as the silvery, 
air-clad species. It constructs its nest in a singular 
105 
