Overview
Barkflies are tiny soft-bodied insects belonging to the order Psocoptera. Despite their common name, they are not true flies and are only distantly related to household fly species. Barkflies are most commonly found outdoors on tree bark, wooden fences, logs, foliage, rocks, and weathered surfaces where they feed on microscopic organic materials such as algae, fungi, lichens, pollen, and decaying plant matter.
These insects are usually harmless and beneficial in outdoor ecosystems because they help clean organic buildup from natural surfaces. Barkflies are often overlooked due to their small size, but under favorable humid conditions they may appear in noticeable colonies on tree trunks or wooden structures.
Although barkflies are occasionally mistaken for pest insects such as termites, ants, or tiny beetles, they do not damage healthy wood, living trees, stored products, or household structures. Their presence is generally associated with moisture and fungal growth rather than destructive activity.
Quick Facts
- Order: Psocoptera
- Common Name: Barkflies
- Habitat: Tree bark, fences, logs, shaded wood surfaces
- Diet: Algae, fungi, lichens, pollen, organic debris
- Status: Harmless scavenger
- Size: Usually less than 1/4 inch long
- Activity: Most active in humid conditions
- Behavior: Colony-forming surface feeder
Taxonomy and Classification
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
- Order: Psocoptera
Barkflies belong to a diverse group of insects commonly referred to as psocids.
This group also includes:
While barkflies live primarily outdoors, booklice are more commonly associated with indoor environments and stored materials.
Barkflies are considered primitive insects with soft bodies and chewing mouthparts adapted for grazing microscopic organic films from surfaces.
Identification
Barkflies are very small insects that may appear as moving specks on bark or wooden surfaces.
Common identifying features include:
- Soft elongated body
- Tan, gray, brown, or translucent coloration
- Long thread-like antennae
- Large visible head
- Short legs adapted for crawling
Many species possess delicate transparent wings held roof-like over the body, while others remain wingless throughout adulthood.
Adults usually measure:
- Less than 1/4 inch long
Under magnification, barkflies may resemble tiny cicadas or aphids.
Large groups may appear as:
- Gray patches
- Moving colonies
- Tiny clustered insects on bark
Some species produce silk webbing over bark surfaces, giving colonies a thin sheet-like appearance.
Distribution and Habitat
Barkflies are widely distributed throughout North America and occur in many humid outdoor environments.
They are especially common in:
- Forests
- Woodlands
- Parks
- Residential landscapes
- Orchards
- Gardens
Preferred habitats include:
- Loose bark
- Tree trunks
- Wooden fences
- Weathered siding
- Mulch
- Decaying wood
They thrive in areas with:
- High humidity
- Shade
- Poor airflow
- Fungal growth
- Persistent moisture
Populations often increase after:
- Rainy weather
- Periods of high humidity
- Extended damp conditions
Life Cycle
Barkflies undergo incomplete metamorphosis.
Egg Stage
Females lay tiny eggs in protected crevices on bark, wood, or vegetation.
Eggs may be hidden beneath:
- Lichen growth
- Organic debris
- Loose bark
Nymph Stage
Nymphs resemble smaller wingless adults.
As they grow, they molt several times before reaching maturity.
Nymphs feed on the same organic materials as adults.
Adult Stage
Adults continue feeding and reproducing throughout warm humid conditions.
Population growth can occur rapidly when moisture levels remain consistently high.
Behavior
Barkflies are primarily scavengers and surface grazers.
They feed on:
- Algae
- Fungal spores
- Lichens
- Pollen
- Organic films
- Microscopic debris
Unlike termites or beetles, barkflies do not consume:
- Structural wood
- Living tree tissue
- Stored food products
They are commonly observed moving slowly across bark surfaces while grazing.
Some species gather in:
- Loose colonies
- Silk-covered groups
- Clusters along bark crevices
Barkflies are highly dependent on moisture and typically disappear when conditions become dry.
Ecological Importance
Barkflies serve an important ecological role as scavengers and decomposers.
They contribute to:
- Breaking down organic matter
- Cleaning bark surfaces
- Recycling nutrients
- Supporting forest ecosystems
By feeding on fungi and algae, barkflies help regulate microbial growth on tree bark and wooden surfaces.
They also serve as prey for:
- Spiders
- Predatory insects
- Birds
- Mites
Pest Status
Barkflies are generally considered harmless insects.
They do not:
- Damage healthy trees
- Destroy wood
- Infest stored foods
- Bite humans
- Transmit diseases
Their presence is more accurately viewed as an indicator of:
- High humidity
- Organic buildup
- Fungal growth
- Moisture retention
Because they gather in colonies, they are sometimes mistaken for more serious pests such as:
- Termites
- Springtails
- Booklice
- Tiny ants
However, barkflies are far less problematic than these insects.
Indoor Activity
Indoor appearances are uncommon and usually accidental.
If barkflies appear indoors, it often indicates:
- Excess moisture
- Poor ventilation
- Water leaks
- Condensation problems
- Mold or mildew growth
Common indoor locations include:
- Window sills
- Damp basements
- Bathrooms
- Attics with moisture problems
- Areas near leaks
Indoor populations rarely survive once moisture issues are corrected.
Signs of Activity
Common signs of barkfly activity include:
- Tiny insects clustered on bark
- Moving colonies on fences or siding
- Small silk-covered patches on tree bark
- Increased activity during humid weather
They are most visible after rain or during warm humid conditions.
Prevention
Preventive measures focus primarily on reducing moisture and organic buildup.
- Reduce moisture accumulation on wooden surfaces
- Improve airflow around trees and structures
- Trim dense vegetation near buildings
- Limit fungal and algae growth
- Address drainage issues
- Remove excess organic debris
- Allow sunlight to reach damp areas
Drying affected surfaces is often enough to eliminate barkfly activity naturally.
Control Methods
Control is rarely necessary because barkflies are harmless scavengers.
Mechanical Control
- Wash surfaces with water
- Remove excess algae or organic buildup
- Improve ventilation
Environmental Control
- Reduce humidity
- Increase sunlight exposure
- Correct moisture problems
- Repair leaks
Chemical Control
Insecticides are almost never required for barkflies.
Most populations disappear naturally once environmental conditions become less favorable.
Interesting Facts
- Barkflies are not true flies despite their name.
- Some species create communal silk coverings over bark surfaces.
- They are closely related to indoor booklice.
- Barkflies help clean bark by feeding on fungi and algae.
- Large colonies may suddenly appear after rainy weather.
Conclusion
Barkflies are tiny harmless insects commonly found on tree bark, fences, logs, and damp wooden surfaces throughout North America. Although they sometimes appear in noticeable colonies, these insects are beneficial scavengers that feed on fungi, algae, lichens, and organic debris rather than damaging wood or plants. Their presence usually indicates moisture and microbial growth rather than a serious pest infestation. Improving airflow, reducing excess moisture, and minimizing organic buildup are typically all that is needed to manage barkfly activity.