You are cozy and warm in your bed, having just dozed off to sleep, when you are suddenly awakened by the buzzing sound of a mosquito in your ear. You jump out of bed and turn on the lights, only to realize that the mosquito has disappeared! You weren’t imagining it--there was a mosquito buzzing in your ear, but because of its tendency to feed in the dark, it hides when the lights are on.

This elusive mosquito is called the house mosquito (Culex pipiens) because of its preference for entering homes to feed on unsuspecting hosts while they sleep. Culex pipiens mosquitoes prefer to lay their eggs in polluted water such as catch basins, standing water under homes, and neglected swimming pools and spas. But the most common place these mosquitoes can be found reproducing in is septic tanks, due to their warmth and the extremely high organic content of the water. There are various septic tank designs ranging from engineered to traditional, all of which can produce mosquitoes.

You must be asking yourself, “How can mosquitoes access my septic tank?” Mosquitoes can enter septic tanks through surprisingly tiny openings such as cracks in the lids, missing screws, and chipped risers. They can also enter through the vent pipe attached to your home.

Septic tank full of mosquitoes. View the rest of the gallery for a few examples of ways mosquitoes can enter septic tanks.

Chipped riser

Chipped concrete septic tank lid

Septic tank covered with weathered plywood

Wood septic tank lid that is warped and falling apart

One septic tank can produce thousands of mosquitoes per week. These mosquitoes, once dispersed, can enter other septic systems in your neighborhood, lay their eggs, and start new populations. This often results in neighborhood-wide problems with mosquito bites. Culex pipiens can also transmit mosquito-borne viruses such as West Nile virus, a potentially life-threatening illness.

Here are a few ways to prevent mosquitoes from reproducing in your septic tank:

• Cover exposed septic tank lids with plastic and several inches of dirt or sand.
• Check for cracks in septic tank lids and seal or replace lids to ensure a tight fit.
• Be certain that lids are fastened and properly secured.
• Screen vent pipes with a mosquito-proof screen (1/16-inch fine mesh).
• Some septic tank lids have screws and gaskets which allow for a tight seal. These screws and gaskets need to be inspected and replaced to maintain a proper seal.

If you are experiencing a mosquito problem, we can help! Submit a request for service online at www.msmosquito.org or call our office at 707-285-2200.

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