THE WOOD-LOUSE. 



463 



sometimes found in such numbers among old 

 furniture and neglected chambers, exposed to 

 the south, that, wanting other sustenance, they 

 devour each other. They are also enemies to 

 other vermin, and destroy fleas very effectu- 

 ally ; so that we seldom have the double per- 

 secution of different vermin in the same bed. 

 Of the bug kind Linnaeus reckons up forty. 



CHAP. VII. 



OF THE WOOD-LOUSE AND ITS VARIETIES. 



THE common wood-louse is seldom above 

 half an inch long, and a quarter of an inch 

 broad. The colour is of a livid black, espe- 

 cially when found about dunghills, and on the 

 ground ; but those that are to be met with un- 

 der tiles, and in drier places, are of the colour 

 of the hair of an ass. It has fourteen feet, 

 seven on each side ; and they have only one 

 joint each, which is scarcely perceivable. It 

 has two short feelers, and the body is of an 

 oval shape. When it is touched it rolls itself 

 up into a sort of ball ; and the 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 

 qnd all sorts of buildings. The male is easily 

 distinguishable from the female, being less 

 and more slender. The eggs they lay are 

 white and shining, like seed-pearls, and are 

 very numerous : however, more properly speak- 

 ing, although, when excluded, the young have 

 all the appearance of an 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 vivi- 

 parous. The little worms at first seem scarcely 

 able to stir ; but they soon feed, and become 

 very brisk. These animals are of great use 

 in medicine, being impregnated with a saline 

 quality, which is diuretic and stimulating. Of 

 this insect, Linnaeus makes three species. 



CHAP. VIII. 



OF THE MONOCULUS; OR, ARBORESCENT 

 WATER- FLEA. 



THIS animal, which is of the size of a flea, 

 appears to the sight, unassisted by the micros- 

 cope, 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. The structure 

 >f the eye is seen, by the microscope, to be re- 



ot the < 



ticulated, or made like a net; and the trunk 

 of this insect, by which it feeds, is not only 

 small and sharp, but also transparent. The 

 insects are of a blood-red colour ; and some- 

 times are seen in such multitudes on the sur- 

 face of standing waters, as to make them ap- 

 pear all over red, whence many fanciful people 

 have thought the water to be turned into blood. 



Swammerdam tells us of a celebrated pro- 

 fessor at Leyden, who was at first astonished 

 by an appearance of this kind. Being once 

 intent upon his studies, he heard a noise, of 

 which, as it increased by degrees, he was de- 

 sirous to know the cause. The maid-servant 

 attending to his summons, appeared quite pe- 

 trified with fear, and told him with a tremu- 

 lous voice, that all the waters of Leyden were 

 turned into blood ! Upon this he went di- 

 rectly, in a small bark, to the place where the 

 water was thus changed, and put some of the 

 bloody water into a glass ; but upon viewing 

 it with attention, he observed, that it abounded 

 with infinite numbers of these little red insects, 

 which tinged the whole body of the fluid with 

 that seemingly formidable colour. Thus his 

 sudden fright was changed into lasting admi- 

 ration. 1 



Of all parts of this animal, its branching 

 arms, arid the motion it makes with them in 

 the water, deserve our greatest attention. By 

 these the little creature can move in a straight 

 line ; waving its arms, as a bird does its wings 

 in the air, sometimes upward, sometimes down- 

 ward, sometimes to the right, sometimes to the 

 left, yet still continuing to proceed in a right 

 line. By striking the water with its arms, it 

 can ascend with great velocity ; and by strik- 

 ing it in a contrary direction, it dives with equal 

 ease. As these motions are very rapid, the 

 little animal appears to jump in the water, its 

 head always tending to the surface, and its 

 tail stretched downward. This insect is pro- 

 duced from an egg, which, when excluded, is 



1 The Cancroid Monoculus. This curious little ani- 

 mal has a convex shell rounded in front, and truncated 

 behind ; the tail is furnished with two bristle-shaped pro- 

 cesses. This insect is by far the largest of the European 

 monoculi ; exhibiting with great distinctness the nume- 

 rous brachial and other parts, which in the smaller spe- 

 cies are only to be viewed by the assistance of the micro- 

 scope. The Linnaean genus monoculus has, by Fabricius 

 Muller, been subdivided into different distinct genera, 011 

 account of the disposition of the eyes, which in some spe- 

 cies are approximated, so as to appear as if single, while 

 in others they are remote from each other. 



The Four-horned Monoculus. This may be consi- 

 dered as one of the most common of the genus to which 

 it belongs, occuring during the whole year in the clearer 

 ponds of stagnant waters, wells, &c. In the size of the 

 body it scarcely exceeds a large mite, but if measured 

 from the extremities of its limbs, will sometimes be 

 found to equal the eighth of an inch in length. The fe- 

 male is, in general, distinguished by the remarkable ap- 

 pearance of the ovaries, which bear a resemblance to a 

 double cluster of grapes in miniature. 



