# Why do mosquitoes need stagnant water? **URL:** \ **Category:** Factual Questions\ **Created:** [June 30, 2015, 11:25pm UTC](https://boards.straightdope.com/t/why-do-mosquitoes-need-stagnant-water/723918 "2015-06-30T23:25:59Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 30, 2015, 11:25pm UTC](https://boards.straightdope.com/t/why-do-mosquitoes-need-stagnant-water/723918/1 "2015-06-30T23:25:59Z")
One of my campers asked me a great question today. By “great question”, I mean one to which I didn’t know the answer (at least, not yet). We were sitting next to an ornamental pond, and she noticed that the pond had two levels, and a pump to move water from the lower to the upper. I said that that would be to prevent the pond from being a breeding spot for mosquitoes, because they need stagnant water. But why, she asked? After all, flowing water would move the eggs downstream with them, thereby further dispersing the mosquitoes, and allowing them to expand to other areas more quickly. Surely, that would be good for them? All I could say at this was that she had a good point, and I’d find out the answer. So, entomologists, why? ---
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [June 30, 2015, 11:43pm UTC](https://boards.straightdope.com/t/why-do-mosquitoes-need-stagnant-water/723918/2 "2015-06-30T23:43:03Z")
As I understand it, the mosquito larval phase is an air-breathing algae eater, so they need to grow up in an environment that is calm enough that they can hang out mostly at the surface, and stagnant enough that algae builds up for them to eat. A flowing steam would not have either of those properties. ---
**Author:** ![Terminus\_Est](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/terminus_est/32/3087_2.png) [@Terminus\_Est](https://boards.straightdope.com/u/Terminus_Est)\ **Post date:** [July 1, 2015, 12:55am UTC](https://boards.straightdope.com/t/why-do-mosquitoes-need-stagnant-water/723918/3 "2015-07-01T00:55:32Z")
The key trait is that mosquito larvae are air breathers. Here’s an image of larvae congregating at the surface of the water to take in air: [![](https://upload.wikimedia.org/wikipedia/commons/c/ce/Culex_sp_larvae.png) ](https://upload.wikimedia.org/wikipedia/commons/c/ce/Culex_sp_larvae.png) You can see that they attach to the surface of the water through a snorkel-like appendage. This requires good surface tension and hence the water needs to be still for it to work. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 1, 2015, 1:34am UTC](https://boards.straightdope.com/t/why-do-mosquitoes-need-stagnant-water/723918/4 "2015-07-01T01:34:49Z")
Huh, interesting. So even just something that made a lot of ripples on the top of the water without moving it anywhere in bulk would work, then? ---
**Author:** ![Nefario](https://avatars.discourse-cdn.com/v4/letter/n/59ef9b/32.png) [@Nefario](https://boards.straightdope.com/u/Nefario)\ **Post date:** [July 1, 2015, 1:47am UTC](https://boards.straightdope.com/t/why-do-mosquitoes-need-stagnant-water/723918/5 "2015-07-01T01:47:32Z")
> [@Terminus\_Est](#): > > You can see that they attach to the surface of the water through a snorkel-like appendage. This requires good surface tension and hence the water needs to be still for it to work. My grandmother’s technique for preventing “wiggletails” in her rain barrel was to pour a little lamp oil on top the water so they couldn’t breathe. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [July 1, 2015, 1:52am UTC](https://boards.straightdope.com/t/why-do-mosquitoes-need-stagnant-water/723918/6 "2015-07-01T01:52:14Z")
> [@Nefario](#): > > My grandmother’s technique for preventing “wiggletails” in her rain barrel was to pour a little lamp oil on top the water so they couldn’t breathe. Putting a thin layer of oil on the surface is a rather standard mosquito-abatement technique. It is also used on much larger scales too, for example, to wipe out mosquitos in malaria swamps. ---
**Author:** ![Bert\_Nobbins](https://avatars.discourse-cdn.com/v4/letter/b/aeb1de/32.png) [@Bert\_Nobbins](https://boards.straightdope.com/u/Bert_Nobbins)\ **Post date:** [July 2, 2015, 2:07pm UTC](https://boards.straightdope.com/t/why-do-mosquitoes-need-stagnant-water/723918/7 "2015-07-02T14:07:18Z")
Mrs Nobbins and I tried this in our garden pond. We put in a fountain and I confidently predicted there would be no more larvae. Dead wrong. They just congregated at the edges of the pond where the water was moving least. (but definitely continually moved by ripples) I think to make it work you’d need something like a jacuzzi. Oh, and foxes kept pulling the fountain out of the pond to play with it. ---
**Author:** ![Maastricht](https://avatars.discourse-cdn.com/v4/letter/m/a88e57/32.png) [@Maastricht](https://boards.straightdope.com/u/Maastricht)\ **Post date:** [August 5, 2015, 1:12pm UTC](https://boards.straightdope.com/t/why-do-mosquitoes-need-stagnant-water/723918/8 "2015-08-05T13:12:26Z")
In ponds, a better way to fight mosquito larvae is by introducing pond fish that eat them. Your local garden supply store will know and sell a suitable fish.