Notes on the Predaceous Habits of the Gray Field Slug, Deroceras laeve12

Abstract

Small numbers of the gray field slug, Deroceras laeve (Mulier), appear in home gardens at Yakima, Wash., during the summer and feed there sparingly on many plants. Damage is done chiefly to seedling plants and to tomato fruits that ripen on or near the ground, but the slugs are of most concern because of their repulsive appearance and the faint trails of mucus that they leave behind them. The literature on the food habits of this and other species of slugs indicates that, with few exceptions, these animals are phytophagous. For example, Isaac (1922) reported that a common garden slug bores into the galls made by a turnip gall weevil, Ceutorhynchus pleurostigma (Marsham), and consumes the grubs as well as the surrounding plant tissue. In New Zealand, eggs and larvae of the sawfly Antholcus varinervis (Spinda), which are found on leaves of piripiri ( Acaena ), are reported to be fed upon by slugs (Anonymous 1946). Kuhnelt (1961) and Mc E. Kevan (1962) reported that several species of snails are predaceous, and Sweetman (1958) predicted that the use of mollusks in biological control was in its infancy.