5H 
THE LIVING WORLD. 
The Jerbillies ( Gerbillince) suffer constant depredation from a horned 
viper [vipera cerastes ), whose appearance alone might well affright the timid 
little creatures, even though the snake’s designs were not known to be murderous. 
The jerbillies vary in length from two to three feet, and are clad in a tawny, 
yellow, shell-like armor, marked with brown to increase the resemblance to the 
sandy soil, in which it burrows. It is distinguished for having very short fore 
feet and hind limbs of very great length, so that its locomotion is identically, 
like that of the kangaroo. The tail is equal to the length of the body. 
The Harvest Mouse [Mus minutus) is somewhat smaller than our common 
house-mouse, which it resembles. Its hair is brown but tipped with red, and it 
it white on the under parts. It hangs its nests to stems of straw and stubble, 
and weaves them into perfect spheres of fine grass. It leaves no opening, and 
naturalists have not yet decided how it provides for its young. 
The Brown, or Norway Rat (Mus decumanus ), has a body eight to ten 
inches long, and the tail six to eight inches, scantily covered with hair and 
about two hundred rings. The color above is grayish-brown mixed with rusty, 
grayer on the sides and ashy white below; the upper surface of the feet dirty 
white. This species, originally from India and Persia, entered Europe through 
Russia, appearing in the central countries about the middle of the eighteenth 
century; it was brought to America about 1775, and has since greatly increased 
in numbers, driving out here, as in Europe, the black rat, which had been 
previously introduced. It is now generally distributed over the world, having 
been transported thither in ships, and is most abundant near the sea-coasts. 
Its haunts are well-known to be cellars, sewers, canals, docks and similar dirty 
places, wherever it can make a burrow or find sufficient food. It is a great 
household pest, and so prolific that its devastations are sometimes very great. 
It breeds from three to five times in a year, having twelve to fifteen at a 
birth, the males always being the most numerous. Not only the black rat, 
but other species indigenous to the old world, are driven off or destroyed by it; 
the dead and even living persons are attacked by it when hard pressed; it is 
not only pursued by man, dogs and cats, but the stronger will kill and devour 
the weaker of its own species. 
The Black Rat (Mus rattus) is seven or eight inches long, with a tail of 
eight and a half inches. The color is very dark, often nearly black, with 
numerous long hairs projecting from the short and soft fur, lead-colored beneath 
and the feet brown. It has a slighter form than the brown rat, with the upper 
jaw more projecting, the ears larger, and the tail much longer in proportion. 
It is not very strong, but exceedingly active; being rather timid, it is exter¬ 
minated by the larger and fiercer brown rat; the habits of the two species are 
much the same, but the black rat is less a burrowing animal, and prefers the 
upper parts of the houses to the cellars and dirty places. It used to be the 
common house-rat of Europe and warm countries until driven off by its con¬ 
gener; it appear to have been brought to the new world about the middle of 
the sixteenth century; it came originally from Central Asia and, like the preced¬ 
ing species, it is omnivorous. 
The Roof, or White-bellied Rat (M. tectorum ), is about six and a half 
inches long, and the tail about eight, with two hundred and forty rings; 
it is colored above like the brown rat, the lower parts and upper surface 
of feet yellowish white; the head is rather blunt, the eyes large, whiskers 
