Insect

Caddisfly

Hydropsyche spp.

Low Risk

Biology

Hydropsyche caddisflies are moth-like insects 8–20 mm long with hairy tent-shaped wings and long antennae. Larvae are aquatic, spinning silk retreats and capture nets in flowing water.

Behaviour

Adults are nocturnal, strongly attracted to lights, and gather in dense resting clusters on walls, screens, and signage near lakes and rivers. They do not bite or feed on structures.

Habits

Accumulations of shed wings and scales can trigger asthma and allergic reactions in sensitive people. Clusters stain siding and clog outdoor light fixtures and air intakes.

Control methods

1Reduce or shield lighting on waterfront elevations
2Use warm amber or motion-activated exterior fixtures
3Wash down walls and fixtures to remove scales and debris
4Install tight screens on windows, vents, and air intakes
5Vacuum indoor clusters rather than crushing them
6Protect sensitive occupants with filtration during peak flights

Tailored to Caddisfly

IPM Procedure Checklist

View full procedure

Step 1

Inspection

Inspect harborage near food, water and warmth
Check cracks, voids and appliance interiors
Place sticky monitors at suspected hot-spots

Step 2

Identification

Confirm Caddisfly (Hydropsyche spp.) — not a look-alike
Note life stage and risk level: Low
Capture clear photos and samples for the record

Step 3

Action Thresholds

Tolerate low-level activity outside sensitive zones
Act if activity moves indoors or near food
Review threshold seasonally with the client

Step 4

Prevention

Seal cracks, plumbing penetrations and wall voids
Eliminate moisture sources and standing water
Improve sanitation: sealed food storage, grease removal

Step 5

Control Methods

Reduce or shield lighting on waterfront elevations
Use warm amber or motion-activated exterior fixtures
Wash down walls and fixtures to remove scales and debris
Install tight screens on windows, vents, and air intakes

Step 6

Monitoring & Evaluation

Service monitors on schedule and trend captures
Re-inspect for Caddisfly activity at follow-up
Adjust tactics based on data; report findings to client