These sites are dry most of the year, but may become filled with water from overflowing streams or polluted runoff from heavy rainfall.

Catch basins lack surface duckweed and cattails, but the margins often are lined with grassy vegetation, shrubs, and small trees.

Catch basins typically do not support fish and insect predators, even when holding water for a few weeks.

Mosquito larvae may develop in virtually any shallow, non-flowing water.

These sites may be inundated by rainfall, snow melt or rainfall run-off.

Aedes and Psorophora mosquitoes deposit "delayed-hatching" eggs in sites that previously held water such as catch basins.

Tremendous numbers of adult Aedes and Psorophora mosquitoes may emerge from these sites several days to a week or so after the eggs have been covered with water.

Aedes and Psorophora mosquitoes inflict painful bites, but our most common species typically do not transmit disease agents to humans.

The very common Aedes species known as "floodwater mosquitoes" inflict painful bites.

Floodwater mosquitoes can disperse many miles in suburban and urban areas.

Polluted catch basins that hold water for at least several days are attractive to species of Culex mosquitoes capable of transmitting West Nile virus.

Females lay eggs on the water surface that hatch in 2-3 days and adults emerge within a week.

Culex females do not disperse far, typically feeding near the breeding site of larvae.

Female Culex mosquitoes typically feed on birds, but will feed on humans and are capable of transmitting West Nile virus.

You have a greater chance of being bitten by Culex mosquitoes if you are outside from dusk to dawn when females are active and searching for a blood meal.

This is why catch basins in urban areas are an important source of vector mosquitoes.

To protect yourself from mosquito bites, wear an approved repellent and avoid being outdoors from dusk to dawn when mosquitoes are active.

Click here for more information on these mosquito species.

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