Sod webworm pupae rarely are observed since they resemble a small clod of earth. In approximately one week, sod webworm adult moths emerge from their pupal case to mate and lay eggs. Flights are most common shortly after dark. The female moth flies low over the lawn area and scatters its eggs. Although adult moths have a short life span, usually less than two weeks, female moths can lay up to 60 eggs per evening.
Sod webworms have one to two generations per year in Colorado.
When a second generation occurs, peak larval feeding and damage is in July. One common species of sod webworm, known as the cranberry girdler, feeds on grass roots rather than blades. Cranberry girdler caterpillars feed primarily in September and October , which causes a later season injury than is typical of other sod webworms. Cranberry girdler caterpillars are recognized by their orange head with indistinct body markings.