68 
Water Spider. — When dredging some ponds the net will often 
contain a few specimens which are unmistakably spiders. They are 
quite dry, and yet a moment before they were below the surface of 
the w aier. T » ese creatures are specially designed to lead an aquatic 
existence. Like their terrestrial brothers, they breathe atmospheric 
air, and have no power of extracting the dissolved oxygen from the 
water as fishes do. The e spiders are densely covered by short 
hairs which are not easily wetted. Consequ ntly, when they 
descend nelow the surface of the water by crawling down the stem 
of some aquatic plant, a quantity of air adheres to the creatures’ 
bodies and gives them the apoearance of globules of silver. This 
air sticki g to their abdomens supplies them for some time with 
the oxygen necessary for respiration. When this is exhausted, the 
creatures have to revisit the surface for a fresh supply. They have 
also another method which enables them to stay below the water for 
a number of hours. Each spider spins a silken chamber among the 
water weeds, which, when complete, resembles a bell, the open end 
pointing downwards. The spider then pays a visit to the surface, 
walks down the stem of some water plant with a bubble of air adhering 
to its body, stands below its newly-constructed cell and .shakes itself. 
Some of the air is dislodged from the creature's body, and in rising 
is caught in the silken chamber above. This process is repeated till 
the -pider is satisfied with the amount of air it has stored. Then off 
it goes in search of food. This consists of any insect not too strong 
to master, and it may be caught either below the surface or on the 
leaves of" some plant growing on the margin of the pond. The 
capture is made not by snaring, as in most other spiders, but by a 
sudden p >unce. Should the victim offer any considerable resistance, 
poison is promptly injected by its captor. This has a very quieting 
and stupefying effect, and without further trouble the spider carries 
it down to its cell and devours it at leisure. If this silken apart- 
ment be torn, another is quickly constructed, for the creature spends 
most of its time there. A special one is woven by the female to 
receive the egg-cocoon. During the winter respiration is all but 
absent, and these spiders shut themselves up in their silken homes 
till the return of spring, when once more their energies are re- 
newed. 
AQUATIC INSECTS. 
Water Boatman. — Any one who goes cautiously up to the edge 
of almost any pond, during the spring and summer months, will 
notice a number of dark coloured insects floating on the surface. 
At the least sign of danger they rapidly dive, but they rise again as 
quickly as they disappeared. These are the insect- popularly called 
Water Boatmen, on account of their two oar like legs which propel 
them. Curiously enough, thry swim on their hacks and breathe 
through their tails, rising constantly to the surface to renew their 
air supply. If one be taken from the water and placed on land, it 
will jump and hop about by means of these oar-like legs, and crawl 
lit- e any other insect wi'h its back uppermost. Then it will he 
noticed that the dorsal parts are light-coloured, and that four wings 
are wrapped tightly against its body. When returned to the water 
it immediately assumes its favourite inverted po-ition. It is very 
predaceous, feeding on any animal, dead or alive, altogether re- 
gardless of its size. If a number of these insects be kept together 
without food, after a day or two only one will remain, and the 
indigestible portions of the others, such as legs and wings, will he 
scattered round the containing vessel. They are strong fliers so 
that the aquarium in which they are confined should be kept 
covered. The female lays her eggs on the submerged stems of water 
