[wolfekeeper (OP)]

Particularly during the summer months I notice that there are little clouds of midges and other flying insects. They often seem to form above relatively high points on hedges and around plants or trees in little flocks of insects.

My question is, doesn't it take a lot of energy to be flying around so energetically, so why do they form in these little clouds like that?

[Don_1]

I know what you mean here. Sometimes I have to drive along the A13 through Rainham Marshes in Essex. Swirling towers of mosquitoes several feet wide and many feet high can be seen from a mile off and more.

This question was asked a while back http://www.thenakedscientists.com/forum/index.php?topic=22445, but I don't think we really tackled it.

So lets have another go. Here's my thoughts:

If these great swarms were to land, they would cover a vast area and being 'grounded' they would have little defence against predators. In these airborne swarms, they are out of the reach of terrestrial predators and birds might be reluctant to attack such a vast number of the blood suckers, for fear of becoming the predated rather than the predator. It might also be possible that these swarms confuse birds, looking, as they might, like a single huge organism.

There is also the 'safety in numbers' aspect. While grounded, those on the edges would be vulnerable to predation. By swarming, each individual can attempt to get on the inside of the swarm, where they are at less risk.

There's one hypothesis, let's see if someone else can come up with another.

[wolfekeeper (OP)]

I think it's to do with predation and geometry. If an insect is sitting, and a predator flies directly towards it, it won't see it coming until it's far too late, the size of the predator on the eye will be very very small, then small, then suddenly huge, but by then it's lunch- there's no lateral movement on the retina, it's really hard to spot the predator coming. (This happens with aircraft- aircraft pilots find it really hard to spot other aircraft that are on a collision course.)

Whereas if you're flying in a straight line, things are better, the insect will see the predator coming unless the predator is tracking the insect (dragonflies tend to sit on the ground, and then fly up to an insect keeping a constant angle to its eye to avoid being spotted too early.)

So house flies take this to another level, instead of flying in straight lines from A-B, they make lots of zig-zags. Unless the predator can make the SAME zigzags then the fly can spot the relative movement and take avoiding actions.

From the point of view of the dragonfly though, even if it can track the fly, there's a big problem- it can only track the movements of one fly at a time! So if there's a cloud of flies all doing their own things, if it flies towards the cloud, the cloud will all simultaneously take avoiding action except for one fly that it tracks which won't be able to spot it.

Except even then the fly WILL notice all the rest of the cloud scarpering for no obvious reason, and immediately take evasive maneauvers, and is virtually certain to survive!

Anyway, that's my theory.

[evan_au]

I have a simpler explanation: sex.
Animals (and humans) will expend a lot of energy and take significant risks for sex.

[wolfekeeper (OP)]

So you're saying that a same-sex cloud won't form?

[chris]

I presume scientists have sexed clouds of midges and mosquitoes? What is the composition?

[Colin2B]

I presume scientists have sexed clouds of midges and mosquitoes? What is the composition?

They appear to have studied it at a place called Cambridge.

When are midges most visible?
Eminent ecologist Dr Henry Disney says:
“Midges are easiest to spot when groups of them dance in mid-air.  What you’re seeing are the males saying to the females: here we are, where are you? They give off a signal that's partly smell and partly sound. If you watch really carefully, you might see a pair of midges dropping out of the group to mate. Midges swarm near an object such as a branch which gives them a point of reference”
Lots of other interesting midge facts - http://www.cam.ac.uk/research/features/whats-the-point-of-midges-and-how-do-you-stop-them-biting

Apparently, little things amuse big minds.

[glot]

mating.

[evan_au]

So you're saying that a same-sex cloud won't form?

A spectacular example is synchronised fireflies, where the males flash in synchronism to attract a mate.

In most species, the male put on the more flamboyant display, and takes the greatest risks of death in putting on these conspicuous displays.

For humans, you could argue that the average female puts more effort into a flamboyant display - although some individuals put a lot of effort into their abs, their car or their university degree. Still, human males tend to die younger.
See: https://en.m.wikipedia.org/wiki/Lek_mating

[alancalverd]

Micro-aerodynamics is quite different from the simple linear stuff of large aeroplanes. Lots of tiny beasties with flapping wings flying within a couple of wingspans of each other are actually sharing energy by flying in each others' vortices, and the whole swarm is probably riding a thermal or some other small local gust, so it's an efficient way of getting from A to B, socialising within swarm, or  protecting a queen and her drone suitors.

Insects are particularly good at long- and short-range meteorology. The migrating Red Admiral butterfly works its way from Spain to northern France or the Netherlands on the prevailing SW winds of the Atlantic lows, then waits for a polar high to provide 2 or 3 days of stable NE wind to bring the swarm to the British Isles.

There was a very telling line in "I Love Lucy" about 60 years ago. Lucille Ball was annoyed with a parrot, and shouted "Stupid bird!". Parrot replied "I can talk.Can you fly?" Whenever we look at the behavior of another species it's important to remember that they have been doing it for millions of years, so it must be the right thing to do, and they never elected an idiot to the White House.

[Colin2B]

For humans, you could argue that the average female puts more effort into a flamboyant display

Not always the case, good examples from English history eg Cavaliers.

[jeffreyH]

Dr Henry Disney sounds like he should be making cartoons of fireflies. @alancalverd Donald Trump is another species and a very stable genus.