What are the orange slugs with feet that keep eating my plants?

Dusky, red and Spanish slugs are orange slugs that eat plants. Taxonomists categorize the three molluscs respectively into the gastropod genus Arion subfuscus, A. rufus and A. vulgaris. Slugs may be considered as beneficial in consuming carrion, decaying and living fungi and plants, other slugs, and snails and as pests in eating edible, ornamental and wildflowering plants.