Although most slugs are injurious to vegetation, there is one genus which provides flesh-eating slugs that will feed upon other slugs and even worms. The British Ear-shelled Slug (Testacella halotidea), shown at fig. 162, is one of these. It is about 2 1/2 in. long, deep yellow in colour, and may be recognized by a small ear-shaped shell attached to its back, just above the tail. During the daytime it nests in the soil, and is often turned up when digging; but at night-time it roves abroad in search of the common slugs and snails, and makes war upon them. A foreign species, from South Europe (T. Maugei), has become naturalized near Bristol, and may spread throughout the milder parts of the kingdom in time if encouraged. It has a dark-brown body with a larger shell than the native species. Cultivators should become acquainted with these friendly molluscs, and should educate their employees to take care of them.

Fig. 160. - Caterpillar devoured by the Larvae of Ichneumons, and Caterpillar covered with their Cocoons.

Fig. 161. - Lacewing Fly.

1, Chrysopa perla. 2, Eggs. 3, Larva. 4, Larva magnified 5 and 6, Cocoon (natural size and magnified).