Recently I have heard reports of slug damage to corn, soybean and sunflower. This particularly wet time in Iowa may be conducive to slugs. Although slugs aren't insects (legs or wings are absent and lack a segmented body), they often get lumped in with the bugs. Slugs have a head with a mouth, sensory tentacles and simple eyes. A simple foot produces mucus which aids in water conservation and movement. As slugs move, they leave a trail of mucus behind, sometimes referred to as a slime trail. Because they lack a hardened shell, slugs are able to move through small spaces and soil crevices. There are several slug species in North America, but the most common slug in Iowa crops is probably the gray field slug, Deroceras reticulatum.
Iowa State University
Hodgson, Erin W., "Slugs Like the Wet Weather" (2013). Integrated Crop Management News. 88.