Rat
Collier's New Encyclopedia (1921)
in zoölogy, a name popularly applied to the larger murines, but more strictly applicable to two species, the English black rat (Mus rattus), and the brown, or Norway rat (M. decumanus). The former is a small, lightly built animal, about seven inches long, with a slender head, large ears, and a thin scaly tail longer than the body. In temperate climates the color is a bluishblack lighter on the belly. The species is represented in warmer climates by the Alexandrian rat better known as M. rattus rufescens), (M. alexandrinus, with a gray or reddish back, and white Al AUSTRALIAN KANGAROO RAT under-surface. By later naturalists it is considered as only a variety. The albino and pied rats, kept as pets, also belong to this species, which had its home in India and penetrated thence to almost every part of the world, driving out the native rats, and to be, in its turn exterminated by the brown rat (probably a native of China, where a similar species, M. humiliatus, is still found). The brown rat is much more heavily built than the black rat, grayish-brown above and white beneath; ears, feet, and tail flesh-colored. Melanism often occurs, but such animals may be readily distinguished by ordinary specific differences from the true black rat. Length of head and body eight or nine inches long, tail shorter. Both the species are omnivorous, predaceous, and extremely fecund, breeding four or five times in the year, the female producing from 4 to 10 blind , naked young, which breed in their turn at about six months old . M. fuscipes is the brown-footed rat of Australia; Nesokia bandicota, the bandicoot, or pig rat; and N. bengalensis, the Indian field rat. Figuratively: (1) One who deserts his party (especially in politics), as rats are said to forsake a falling house or a doomed ship. (2) A workman who takes work for less than the regular wages current in the trade; also a workman who takes employment at an establishment where of opprobrium applied to non-union men the regular hands have struck; a term by members of trades unions; specifically to non-union printers. Zealand tree related to various species of RATA (Metrosideros robusta), a New ironwood. The seed is believed to be swallowed by a caterpillar, and to sprout in its interior, the fostering grub being of course killed. The tree begins life trees, and attains a height of 150 feet; as a climber, attached to other forest but when it has killed the supporting stem the rata is able to sustain its own weight and to grow on as an independent tree, attaining ultimately a height of nearly 200 feet. The wood is very hard, formerly much used for making clubs, and is valuable for shipbuilding.
What Has Changed in the Last Century
When Collier's wrote this in 1921 the two rats were still filed under Mus; both are now placed in the genus Rattus, as Rattus rattus and Rattus norvegicus, and the entry's silence on disease is striking, since the rat flea's role in carrying plague bacillus had been worked out in the years around 1898. The brown rat has gone on to become the most important mammal in the laboratory — its genome was sequenced in 2004 — while the black rat has retreated so far in northern Europe that Britain now treats it as a rarity rather than a pest. Rats are also now the target of large island eradication campaigns to save seabirds: South Georgia was declared rodent-free in 2018. The tacked-on note that the New Zealand rata's seed sprouts inside a caterpillar is folklore confused with the fungus that mummifies caterpillars; rata in fact germinates as an epiphyte in the forks of host trees, and the species now faces the arrival of myrtle rust.
Written for this edition, 2026.