During mating, two individuals join to accomplish mutual fertilization. Each mated slug proceeds to lay eggs in moist areas, up to 100 eggs apiece. Baby slugs hatch in one to three weeks and immediately begin to crawl and feed. Development to the full-grown adult stage takes from two months to a year or more, depending upon the species. Iowa slugs generally spend the winter as adults and lay eggs in early spring.
New adults are present by midsummer when a second generation is started.
Management options Slug treatment may be occasionally necessary. Clean up the garden and eliminate slug hiding places as practical. Heavy leaf litter, boards, bricks and other piles of damp debris should be removed. Dense ground covers that are harboring slugs can be thinned to promote sunshine, air circulation and drying. Minor slug problems can be controlled by handpicking.