What larval trait distinguishes *O. brumata* from similar-looking caterpillars within Geometridae?

Larvae characteristically possess only two pairs of prolegs on the abdomen

While many caterpillars within the broader insect orders possess a standard complement of prolegs that provide firm grasping ability, the defining characteristic used to differentiate the invasive *O. brumata* larva from related species, such as some similar-looking Geometrids, is the specific count of its abdominal prolegs. Larvae of *O. brumata* are characterized by having only two pairs of prolegs on the abdomen. This specific number is critical for field identification, especially when assessing defoliation in vulnerable settings like orchards. If larvae are observed arching but exhibit only two visible rear grasping points, it strongly suggests the presence of this specific Geometrid lineage, separating it from caterpillars that might possess three or more such abdominal appendages.