The Nearctic species of Neophyllomyza Melander are revised and descriptions, illustrations, and an identification key are provided for the two included species, N. quadricornis Melander and N. gaulti n. sp. Large numbers of adults of both species were collected in emergence traps on decaying logs of sugar maple (Acer saccharum Marsh. (Aceraceae)) and American beech (Fagus grandifolia Ehrh. (Fagaceae)) in eastern Canada, indicating that the larvae of both species are saproxylic, although their exact food source is unknown. Although the two species are sympatric over much of their range and apparently use the same resources for larval development, their habits differ: N. quadricornis was collected from logs in both the early- and the advanced-decay stage from late May until September, with a peak of emergence in late June, whereas N. gaulti was reared almost exclusively from logs in the advanced-decay stage and from mid-July to mid-August. This suggests that N. gaulti is more specialized in its larval habits, which may reduce competition between the two species.