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Home Maintenance And Repair - 01500547

Nuisance Aquatic Insects, Caddisflies, Stoneflies, and Mayflies

The adults of several types of aquatic insects will frequently emerge in large numbers, causing concern among homeowners. Three types of aquatic insects frequently encountered around homes are caddisflies (Trichoptera), stoneflies (Plecoptera) and mayflies (Ephemeroptera).

Caddisflies are distinct from the other two groups by the hair-covered wings which are held roof-like over the back when at rest. Mayflies have large forewings, small hindwings that are held together at rest over the body. There are also 2 (rarely 3) caudal filaments which are equal to or greater than the length of the body. Stoneflies have a hindwing which is larger than the forewing, and the wings are held flat over the back. There are two caudal filaments, but they are generally shorter (less than half the length of the body). The adults of these insects are generally short lived, especially in the case of the mayflies, and they generally do not feed. Even though homes near aquatic habitats may be covered with resting insects during mass emergences, expensive chemical controls are seldom necessary.

The insects can be allowed to disperse naturally, or they can be removed by sweeping or vacuuming. Those insects which get indoors can be subdued with an aerosol flying insect spray containing pyrethrin, and then removed. An ordinary aerosol hair spray will also subdue flying insects by stiffening their wings and allowing their removal.

These aquatic insects are attracted to lights, and when they are active it may be necessary to reduce outside lighting or switch to yellow light bulbs. These insects are least responsive to the yellow light.

For a complete listing of suggested control options for all home, yard and garden insect pests contact your local Extension Service, found under local government in the phone book.

Read and follow instructions on the pesticide label. Heed all warnings. Check with your physician if you have any concerns regarding your personal health risk.


Tom Ellis, M.S., Department of Entomology.

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This information.was reviewed as of June 2008.  For more information about the contents please contact for webpage problems .