The flowers are cross-pollinated by bees and possibly flies. The Andrenid bees, Andrena tridens and Andrena virginiana, are two such floral visitors of Winterberry. Insects that feed on the leaves of this shrub include the moths, Harrisimemna trisignata (Harris' Three-Spot) and Thysanopyga intractata (Black-Shouldered Gray), and the larvae of a small fly, Phytomyza verticillatae (Winterberry Leafminer). Although the bright red berries are not a preferred source of food, they are eaten by many songbirds and some upland gamebirds (see Bird Table). Because they persist in good condition through the winter, the berries are particularly important as a source of emergency food during the winter. The seeds are distributed to new areas by these berry-eating birds. The White-Footed Mouse eats the berries and its seeds, while White-Tailed Deer browse on the leaves and twigs to a limited extent.