Montana Field Guide

Crambus ainsliellus is a medium sized Crambus (21 - 29 mm wingspan). The forewing is yellowish-brown. The discal silvery stripe is broad, somewhat scimitar shaped, not crossed by dark brown lines and lacks a tooth on the underside of the stripe. The forewing lacks a sinuous white submedial line and a white patch beyond the stripe. The forewing base has a costal brown area that is reduced to a single line. The hindwing is grayish with a dirty white fringe (Powell and Opler 2009).

Shropshire and Tallamy (2025) provide a list, with synonymies, of 13,055 described native, exotic, and occasional straying Lepidoptera species of North America, north of Mexico; known but undescribed taxa, taxa with unresolved taxonomy, and excluded species are also included. The main manuscript includes links to supplementary materials, including a reference list for Lepidoptera of North America north of Mexico, and a filterable spreadsheet with information on taxonomy, synonymy, size ranges of species, distribution by state, province, and country with references, and host-plant Family and Genus associations with references.

C. ainsliellus adults fly from August to September (Powell and Opler 2009).

C. ainsliellus prefers grassland areas (Powell and Opler 2009).

Unknown, but probably grass roots (Powell and Opler, 2009).