There are also costs associated with harvest management including swathing before combining, adding pickup guards to combine, slowing speed at harvest, and damage to combines associated with lower header setting and picking up rocks and soil. Adults are black with a yellow banded abdomen with clear wings that look iridescent in the sun. Their activity peaks between 10 to 11 am when they can be found moving around in wheat fields. Males emerge before females, remaining in fallow areas or in field edges, poised to mate as soon as females emerge, although mating also occurs within the field. Females can be identified by a short ovipositor, used for laying eggs, that protrudes from the end of their abdomen.
Females mate almost immediately upon emerging from stubs and then move wheat to lay eggs.
The 2 nd and 3 rd node from base of plant, certain stem diameters, and plant growth stages are preferred for egg laying. Wheat stem sawfly has been noted to occur in resident, non-cultivated grass species including crested wheatgrass, smooth brome, and quackgrass in Montana. While multiple eggs may be laid within stems, the larvae that emerge are highly cannibalistic with only one larva surviving within a single stem. Larvae have a light brown or tan head and a white body and take on a characteristic S- shape when removed from stem. Larvae feed within the stem on plant pith tissue, boring through nodes as they feed.