Slugs proper are widely distributed, species being found in various parts of both hemispheres; but the temperate regions of the northern hemisphere are principally troubled with them. The common Grey Slug (Limax agrestis) commits great ravages every year in our fields and gardens, notwithstanding the number of birds which make this species their prey; and various means have been devised to get rid of the pest, or at least to diminish its intensity. Quicklime, soot, coal-ashes, and saw-dust, are in turn sprinkled on the ground around tender plants; but the effects of these and similar substances depend upon their dryness, and the inability of the Slug to crawl upon powdery substances. The first shower of rain, however, and even the dews of night, break the spell.
This species varies much in size and colour, being by turns white, pale reddish-grey, and nearly black; but it may be easily distinguished by its body being furrowed with interrupted lines, with a short keel, which is always placed obliquely. The mantle is comparatively large, marked with circular lines; the enclosed shell is very minute, thick, hard, and irregular.
The Grey Slug is very prolific, continuing to lay its groups of eggs from April to the end of November, and depositing from thirty to seventy eggs at each time. The young increase in size rapidly, and reach their full growth in three months from their birth. When irritated, the Slug pours out from the whole surface of its body a copious white mucus, of the consistence of thick white cream, which dries into a white membrane.