Adult females emerge in the spring, cut shallow holes through the lower leaf surface, and deposit eggs under the leaf epidermis. A female lays one to three eggs per leaflet. To feed, the female cuts a hole in the leaf with her oviposter and laps up exposed sap and tissue, forming conspicuous pinholes in the leaves. After the eggs hatch, the larvae tunnel within the leaf, feeding on leaf tissue. The larval stage lasts approximately two weeks.
Larval mining causes conspicuous white blotches on the leaflets, which typically are comma-shaped.
Blotches and punctures can cause deterioration of foliage quality, loss of photosynthetic area, and defoliation. May. Larvae feed within the growing tips, on the upper leaves as they open, and later on the lower leaves. Plants become skeletonized from weevil feeding and the leaves dry, giving the field a frosted appearance. After cutting, the larvae may feed on the new emerging shoots, severely retarding alfalfa regrowth. Adults also feed on the alfalfa plant.