THE WATER FLEA. 
275 
two first pairs of legs. The belly consists of nine rings; 
under which are placed two pair of legs more, making six in 
all. Each leg has three joints, which form the thigh, the leg, 
and the foot, which is armed with a crooked claw, like an 
hook. The body is smooth except a few short hairs, that 
may be seen by the microscope, about the vent, and on the 
two last rings. Its sight is so exquisite, tlmt the instant it 
perceives the light it generally makes good its retreat; and 
they are seldom caught, though the bed swarms with them. 
Cleanliness seems to be the best antidote to remove these 
nauseous insects; and wherever that is wanting, their increase 
seems but a just punishment. Indeed, they are sometimes 
found in such numbers among old furniture, and neglected 
chambers, exposed to the south, that wanting other susten- 
ance, they devour each other. They are also enemies to 
other vermin, and destroy fleas very effectually ; so that we 
seldom have the double persecution of different vermin in 
tile same bed. Of the bug kind Linnaeus reckons up forty. 
The common Wood-lotjse is seldom above half an 
inch long, and a quarter of an inch broad. The colour is of 
a livid black, especially when found about dung-hills, and on 
the ground : bat those that are to be met with under tiles, and 
in drier places, are of the colour of the hair of an ass. It lias 
fourteen feet, seven on each side; and they have only one joint 
each, which is scarcely perceivable. It lias two short feelers, 
and the body is of an oval shape. When it is touched, it rolls 
itself up in a sort of ball ; and tile sides, near the feet, are 
dentated, like a saw. It is often found among rotten timber, 
and on decayed trees : in winter it lies hid in the crevices of 
walls, and all sorts of buildings. The male is easily distin- 
guishable from the female, being less, and more slender. The 
eggs they lay are white and shining, like seed pearls, and are 
very numerous; more properly speaking, however, when ex- 
cluded, the young have all the appearance ofan egg, yet they 
are alive, and, without throwing off any shell, stir and move 
about with great vivacity : so that this animal may properly 
be said to be viviparous. The little worms at first seem 
scarcely able to stir; but they soon feed, and become very 
brisk. ' Of this insect Linnaeus makes three species. 
The Monoculus, or Arborescent \Vater-Flea. 
This animal, which is of the size of a flea, appears to the 
sight, unassisted by the microscope, to have but one eye ; for 
the eyes, by reason of the smallness of the head, seem to be 
joined to each other: they are situated in the trunk of this 
insect, and the beak is likewise very small and sharp pointed. 
