EARTHWORM. The popular name for worms of the family Lumbricidie, especially the common Lambricas terrestris and .tllobophora Retida. They belong to the oligoclurtnus sec tion of the cluetopod annelids, and are widely distributed in temperate and tropical lands.
IlAulTs. Like most other oligochletes, earth are subterranean in their habits, and ap• pear above the surface only under condi tions, such as excessive rain. which floods their underground burrows and forces them to the surface to avoid drowning. They also come to the surface to feed and to throw out their 'cast ings;' but this is almost wholly at night, and although they have no eyes or light-detecting organs, they seem to avoid the light. Earth worms are often seen in great numbers upon sidewalks. steps. and paved after a wet night or a hard rain, and they are often reported to have actually 'rained down.' • Sneh cases, however. are easily explained by the fact that the crawl about actively in their attempt to get out of the water, and even climb up com paratively -month surfaces. and the hard sur face of the sidewalk or roadway prevents their the earth when daylight returns, they are all left exposed to view. Although naturally somewhat sluggish, these worms can burrow with considerable speed. especially in light soil. The burrowing is accomplished not only by fore ing the bluntly pointed head between the par ticles of earth and pressing them apart, but also by actually taking into the mouth and swallow ing notch of the opposing material. In all their movements, the short but stiff set(/' or bristles along the sides of the hotly are of the greatest assistance. These setae are arranged in pairs on each segment. two pairs on each side. so that evcr? segment carries eight seta., and they form two double. longitudinal r(ms along each side of the worm. Earthworm- form the prey of many animals. from slugs upward. and form the prin cipal food of moles. shrews, and the like. Their
habit of going into the water, and the accidents of floods, cause many to fall a prey to fishes: and they are the commonest bait for still-fishing, whence they are more commonly known in the States as than by any other name.
E.iternwoaias Axn Sou.. The important part that earthworms play in the economy of nature was not generally recognized until attention was called to it by (7harles Darwin. 1Iost of our knowledge of the habits of these creatures is due to hint. Earthworms are vegetable feeders ex clusively. In burrowing the worms take more or less earth into the alimentary (-anal, where it is mixed With the vegetable food of the worm, tutu nearly all of it passes out with the cast ings. which are always voided on the surface. These castings are therefore a sort of natural 'compost.' Which the earthworms are continually distributing over the surface of tlie areas which they inhabit. They are thus not only constantly transforming vegetable matter into more usable forms. hut are also so mixing it with inorganic matter as to make both of greater use. Such a process is called the formation of vegetable mold. and it is continually going on wherever the conditions are suitable. It is not, of course, confined to the agency of earthworms, though \Ir. Darwin showed that they were one of the mast important agents. The rate at which veg etable mold may be formed by these worms )gill vary of course with the character of the soil, the number of worms, and the almndance of food, but under favorable conditions it may be sev eral inches in a century. Such soil is fertile not alone beeause of its composition, but because the movements of the worms keep it stirred up and well aerated. For further particulars in reference to the habits and usefulness of earth •(irIns. consult Darwin. The Fm-motion of Vege ta/de Mould Through the .letion of Worms (Lon don. lqSI ).