CSU Extension Slugs , and closely related snails, are classified as gastropods. They are more similar to clams and mussels than other common garden pests such as insects. Slugs feed on a variety of plant materials that they eat by rasping with specialized mouthparts. Most feeding is done during the night, although they occasionally are active during cool overcast and rainy days.
Slugs seek shelter during the day in soil cracks and under debris.
During hot and dry weather, slugs may be temporarily inactive. Slugs lay small masses of eggs in soil cracks. The young slugs that hatch from these eggs travel through the soil and damage germinating seeds and root crops. Under favorable conditions, slugs complete development in a few months.