Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: LeeE on 23/11/2009 15:25:26
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What are hoverflies doing when they're just hovering in the air, apparently doing nothing useful?
Other flying insects are able to navigate and track scents while moving, and as far as I can see, just hovering in the same place would only seem to make it an easier target for predators. However, as they've obviously still around and weren't all eaten long ago, hovering must serve some constructive purpose that outweighs the risk of being eaten.
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I have always assumed they were deciding which is the best target stem for the pick of the aphids, but you're right in that other insects seem to do this 'on the wing' estimation quickly and then land. Perhaps the hoverfly, by being so diligent, manages to avoid capture by spider webs better than its rivals.
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I've seen them doing it for relatively long periods of time, hovering quite a long way from any foliage. They might hover in one place for a few seconds, then move five or six inches to one side, then up or down a bit. This can go one for perhaps tens minutes or more, and even then, when they do fly away, they don't seem to go anywhere in particular or with any obvious sense purpose.
They must be using quite a bit of energy to do all this though, in addition to the possible increased predation risk, so I can't imagine that there's no point to it. The best reason I can think of is that it's related to mating (perhaps trying to locate minute trace scents/pheromones) but I can't ever recall seeing any evidence of mating taking place in connection with this behaviour.
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Have you also noticed they sometimes hover in front of glass, as if they are looking at their own reflection?
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Where they seem to hover just seems pretty random to me, so I wouldn't be surprised to see them hovering in front of glass, especially when the observer might be looking from behind said glass [;)]
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although I did not learn why hover flies hover, I did learn that naked scientists seem pre-disposed to answer within the confines of natural or sexual selection. If Darwin had thought like that he might have ended up a sailor or a ship's chaplain instead of a naturalist. Oh well - back to watching that bright green hover fly in the morning sun on this beautiful spring day in the new time of cholera. Cheers
PS: I'm not even sure we're talking about the same insect. This is what mine looks like (awful hard to get this guy in focus)
-- and I see I'm a "Newbie" -- where else but the internet can an old fart like me be a "Newbie"?
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Apparently there are many different species of hoverflies around the world, with equally disparate tastes...
See: https://en.wikipedia.org/wiki/Hoverfly