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Caloptilia fraxinella are small moths with 12-14mm wingspan. Wing background is gray; forewings have many black and white scales that form spots (Forbes, 1923). A few orange iridescent scales are scattered across the wing surface. The fringes of hind wings, head and thorax are all gray. Male genitalia show the clearest difference between species of Caloptilia. The valves are lobe-shaped instead of notched near tip of ventral margin as in C. alnivorella and C. strictella (Pohl et al. 2004).

Small (0.4mm x 0.3mm) white eggs are laid singly along the midrib of newly emerged ash leaves. Within one week the first instar larvae emerges and begins mining under the upper cuticle of the leaflet. Fourth instars will emerge from the leaflets and use silk to migrate to new leaves in late June. The small (7.3mm) cream coloured larvae will roll the distal portion of the leaf under to create a small cone (fig.1). In mid-July the fifth instar will eat away a small circle of tissue under the upper cuticle; this appears as a white 'window' on a rolled leaf. A cocoon is spun with one opening attached to the window and other to the other side of the cone. After 10-14 days of making the window the pupa pushes itself 1/3 out the window and the moth emerges. Adults will aestivate mid-august and re-emerge in September to find overwintering sites. They overwinter until mid-April to mid-May, which is when they mate (Pohl et al., 2004).

Caloptilia fraxinella larvae mine the top side of the leaves of ornamental green ash (Fraxinus pennslvanica), black ash (F. nigra) and Manchurian ash (F. mandshurica) until third week of June. The final instars of larvae create rolls on the ash or neighboring lilac bushes (Syringa vulgaris) (Pohl et al., 2004).