The woolly alder aphid, also known as the woolly aphid, is a small insect that feeds on alder trees. It is characterized by a white, cotton-like substance that covers its body, which serves as a protective shield. While "woolly alder aphid" is the most common way to refer to this insect, there are some other synonyms that can be used as well. These include "woolly adelgid," "woolly aphid fly," and "woolly beech scale." Each of these names refers to a different variation of this species, but all share the same basic features: a white, wool-like coating and a tendency to feed on tree leaves.