- any plant louse of the family Aphididae, characterized by a waxy secretion that appears like a jumbled mass of fine, curly, white cottony or woolly threads, as Eriosoma lanigerum(woolly apple aphid, or American blight ) and Prociphilus tessellatus(woolly alder aphid ).
- any of various aphids that produce white waxy threads, as Adelges piceae(balsam woolly aphid ).
