Saturday, August 30, 2008

Things I've Been Doing Instead of Blogging: Researching Pressing Questions

Over on Sassy Red Head, Tiana took some time away from tending her adorable newborn to ponder a question that piqued my curiosity:

If you have mosquitos in your house, how likely is it that they would lay eggs in the glass of water on your bedside table as you sleep and then you drink gross mosquito eggs?

Culex quinquefasciatus Ovipositing, photo by smccann

When I came across her question, I went to her comments to see if the question had been answered and no, it hadn't been. So I had to find out for myself. I started typing in my answer and reached my fourth bullet point when I realized it would be easier to do all the HTML in a blog editor, so I'm going to post my literature findings here.

  1. It seems that if eggs are laid, they won't hatch: "To rear your larvae you will have to de-chlorinate tap water by leaving it stand in your glass jar for at least 24 hours. Aedes eggs also hatch better in deoxygenated water."
  2. "A freshly laid egg is light in color and darkens within a few hours. Mosquito eggs are oval and about 1/40th of an inch (0.635mm) long. Eggs are either deposited singly or as an egg raft depending on the type of mosquito. A standard egg raft is about 1/4 inch (6.35mm) long and contains 100-200 eggs." [source]
  3. Depending on the type of mosquito, it might lay eggs on the water surface, or on the side of the glass above the water line. [source]
  4. Aedes vexans appears to be the Ontario mosquito type that most goes after people. [source]
  5. It appears that these mosquitos are almost all laid above the water line and hatch in spring flooding. [source]
  6. So maybe the mosquito in Tiana's house in late August is another kind, possibly culex, which prefer birds (and therefore can catch West Nile virus) and lay egg rafts on open water. [source]

    Culex egg raft, Keremeos BC, photo by smccann

  7. Most mosquitos have to have a blood meal before they can develop eggs. I'm having a hard time finding a source that says how long after their blood meal the eggs come out. [That is to say, I've checked four websites in five minutes, haven't found the answer, so I'm giving up.]
  8. But that's okay, because the Culex pipiens (which may be more common in suburban Ottawa) will lay its eggs in "discarded tires, unwashed bird baths, clogged rain gutters and plastic wading pools allowed to stagnate," but "will not lay its eggs in any of these habitats if the water is too clear". [source]

Conclusion:

Tiana's water glass is safe from mosquito eggs, but if mosquito eggs make her queasy, probably best to stay away from tea that was brewed the day before.

3 comments:

deadmike said...

If the glass of water stinks like rotting leaves or hay, Culex will likely oviposit in it, if there is a gravid female nearby.
Aedes is what is known as a "floodwater" mosquito, so the eggs are laid on a dry surface that will be inundated by rainfall or snowmelt. Therefore, the glass of water is probably safe from them.
Most of the Culex that enter houses are either looking for a blood meal, or a place to hibernate in the fall. Most of the mosquitoes who enter your house, therefore, are not in a physiological state to lay eggs.
As for the time required to mature a batch of eggs, most of Culex I have worked with require between 3-7 days, depending on the temperature.

Tiana said...

Thanks David.

Now I don't have to feel worried when I drink my night time water!

Anonymous said...

Yuk, I had to read this just before eating. Tiana, and others who leave water on their night table, just place something on top of the glass, like I do with the juice I leave on the table all night.
redvera