It has characteristic black spots on its upper surface. The dusky slug is intermediate in size, being one to three inches long, and can range from a gray to a bright orange in color. The eggs appear as perfectly round gelatinous spheres filled with a watery substance. They are usually colorless, often reflecting the color of their surroundings, but they may become cloudy just before hatching. Baby slugs resemble adults but are smaller and may not be as fully colored.
All slugs lay eggs.
Each species requires a different length of time for the development of its eggs and the maturing of its young. The number of eggs laid at one time by one slug may be up to 100, but average 20 to 30. Young adult slugs apparently lay fewer eggs than older ones. Though slug eggs may be found outdoors during any month of the year, most of the eggs are laid in the spring and early summer. Most species overwinter as adults or nearly mature young.