Bark lice are small, common insects frequently found on trees. Despite their name, these creatures are not true lice and do not behave like parasitic insects. This article clarifies whether they pose any threat to trees or people.
Identifying Bark Lice
Bark lice, also known as psocids, are tiny, soft-bodied insects, less than 5 millimeters long. They often appear grey, tan, or brown. Some species have distinctive striped markings or dark, smoky-gray wings with a triangular light spot on each forewing. Their wings, if present, are held in a roof-like position over their bodies when at rest. Bark lice possess long, thin antennae and chewing mouthparts.
These insects are commonly found in groups on tree bark, particularly in humid or shaded areas. Some species produce fine, dense silken webbing that can cover tree trunks and branches, giving the bark a silvery or ghostly appearance. While extensive and noticeable, this webbing is fragile and usually disappears within a few weeks.
Ecological Role and Tree Health
Bark lice do not damage trees and are considered beneficial or neutral to tree health. They feed on superficial growths on tree bark, such as algae, fungi, lichens, mold, pollen, and dead plant tissues. This diet means they act as natural “cleaners” of the tree’s surface, removing accumulated materials.
Unlike other insects that bore into wood or suck sap, bark lice use chewing mouthparts to graze on non-living surface materials. Their presence indicates a suitable habitat with ample food sources, and their webbing offers protection from predators. Therefore, no intervention or control measures are needed to remove bark lice for tree health.
No Threat to People or Animals
Bark lice are not parasitic and pose no threat to humans or animals. They do not bite people or pets, nor do they transmit diseases. Their presence on a person’s body is merely incidental, as they are not adapted to feed on blood or living tissue.
Bark lice are outdoor insects and not considered household pests. While related species, known as booklice, can be found indoors feeding on starchy materials in humid conditions, bark lice primarily inhabit trees. Encountering bark lice should not be a cause for concern, as they are harmless to living creatures.