01/18/2002 - Updated 06:49 PM ET

Mosquito larvae use a snorkel

Q: We're told to avoid leaving shallow containers of water lying around because that's where mosquitoes breed. Do they breed in still bodies of deeper water, like storm sewer catch basins? Is there some depth that's critical to the breeding?

A: Yes, mosquitoes can breed in deep, still water, like storm sewer catch basins. They normally prefer shallow water (e.g., tin cans and old tires) because the larvae cannot survive in wild water. They like deeper water crowded with vegetation, so no waves form. Usually, however, they avoid deep water since it can contain enemies: fish and tadpoles.

I asked Gil Copley, director of the St. Charles County health department in St. Charles, Mo., about a critical depth for breeding. "The deeper the water, the more likely it is to have too much circulation and movement ..."

Scott Camazine, entomologist professor at Penn State University explains why mosquitoes aren't too particular about the still water they breed in. "Mosquito [larvae] can tolerate stagnant pools or shallow or deep water because they do not need to get oxygen from the water." The larvae have a snorkel breathing tube that opens on the surface of the water. Most underwater larvae have gills and get oxygen from the water like fish do. Thus, all mosquito larvae develop very close to the water's surface and breathe air. "There is no critical depth of water."

(Answered by April Holladay, science correspondent, Jan. 16, 2002)

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