Webspinners (order Embioptera), also known as footspinners, are insects distinguished by their unique ability to produce silken galleries in which they live. Found worldwide, especially in warmer climates, they are often noticed by homeowners when their expansive webs appear on tree bark, rocks, or under debris. Understanding their biology and implementing targeted management practices is the most effective way to control their presence.
Identifying the True Webspinner
True webspinners are small, elongated insects, typically measuring 4 to 15 millimeters long. A defining feature is the location of their silk glands, which are found in the enlarged basal segment of their forelegs, earning them the name “footspinners.” They use these specialized glands to continuously weave fine, protective silken tunnels, or galleries, where they spend nearly their entire lives.
Females are always wingless, while adult males may have two pairs of membranous wings used for dispersal before mating. Both sexes have short, sturdy legs adapted for rapid movement, especially darting backward within their tunnels to escape predators.
Understanding Their Behavior and Low Threat Level
Webspinners are gregarious insects, living in communal galleries that are extended as the colony grows. These silken structures protect them from predators and maintain the high humidity and temperature necessary for their survival. Colonies are typically found in sheltered, dark, and moist locations, such as beneath stones, loose tree bark, leaf litter, or embedded in soil.
Their diet consists almost entirely of non-living organic materials, making them beneficial decomposers. They feed primarily on decaying plant matter, moss, lichens, and dead bark. Since they do not consume healthy plant tissue or wood, they are not considered pests that cause structural or economic damage. Aggressive control is usually unwarranted given their harmless nature and ecological role.
Non-Chemical Removal and Habitat Modification
The most effective long-term control involves modifying the habitat to make it less conducive to colony establishment, as webspinners thrive in specific microenvironments.
Mechanical Removal
Mechanical removal involves physically eliminating the visible silken galleries. A stiff-bristled brush or scraper can dislodge the webbing from surfaces like tree trunks, rocks, or foundation walls.
Habitat Modification
Reducing excessive moisture is a crucial step because the insects rely on high humidity to survive. This can be achieved by:
- Improving drainage around the structure.
- Trimming back dense vegetation that traps moisture against the siding.
- Ensuring gutters are clean and functioning properly.
- Eliminating debris that provides sheltered habitat.
Removing or relocating potential nesting sites, such as stacks of firewood, piles of stones, or thick layers of leaf litter near the foundation, will discourage colonization.
Exclusion
If webspinners are found entering a home, sealing exterior cracks and crevices with caulk can block entry points. Regularly sweeping or vacuuming up the silken tunnels in accessible areas will disrupt the colony’s protective environment, forcing them to relocate.
Targeted Chemical Intervention
Chemical treatments are rarely necessary due to the low threat level of webspinners and the effectiveness of non-chemical methods. If a colony is persistent or physical removal is impractical, a targeted chemical application can be used as a last resort.
This intervention should focus on treating the immediate area of the silken galleries rather than broad-spectrum spraying. A residual insecticide dust or liquid spray formulated for outdoor perimeter use, containing active ingredients like pyrethrins or pyrethroids, can be applied directly to the webs and entry points. Dust formulations are often more effective than liquid sprays because the hydrophobic nature of the silk prevents full penetration of the galleries. Always follow product label instructions precisely, focusing application only on affected areas to minimize environmental impact.