babu1's picture

Massed dragonflies

My neighbour tells me that he saw 'thousands' of dragonflies flying around in a local field. This happened about 19th Sept, East Kent.
There is no water near the site apart fom an occasional dewpond/marshy area.
He was astonished and watched for some time.

I've never heard of massed gatherings of dragonflies. Is this a known occurance?
I so wish I'd seen it!

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Amadan's picture

"Thousands of dragonflies"

This is one of those reports that you need to be a bit cautious about, I think.
Creatures that have definite patterns of behaviour (such as flying ants appearing all over the country on the same day) can cause this sort of phenomenon. Dragonflies do tend to emerge from ponds as adults around the same time, so it is possible that this is what was seen: the pond may have been quite small, and it sometimes happens that the water was more extensive when the eggs were first laid.
But what can also happen is that there are many flying insects around, and the observer assumes that, because the ones that can clearly be seen up close are dragonflies, that so are the rest. They might, however, be (for instance), crane-flies.

BDeed's picture

Dragonflies

The other thing to remember is that adult Dragonflies can travel some distance from the pond they emerge from in search of food, we occasionally have Hawkers flying up and down the main road in town and at the back of our terrace (which backs onto another terrace) with no ponds for anywhere nearby.

Perhaps if there was good feeding in the field it may have drawn quite a few? Also be aware that both Dragonflies and Damselflies will use almost any water-body if a suitable pond not available this could well include field ditches, water filled tractor furrows etc...

RoyW's picture

Dragonfly 'swarms'.

It's actually not that unusual to see large gatherings of dragonflies, and because of the species most likely to be noticed this is something which is most often seen in August and September. (I'm a little confused over the date you gave - is this a typo, or was it 19th Sept in a previous year?).

As has been said, large numbers of dragonflies can emerge together, and after emergence dragonflies typically head away from water to spend a few days feeding while they mature. Anywhere where there is a good supply of food available can attract large numbers, including flying ants (as suggested), or simply sheltered sunny areas where plenty of midges and other small insects are flying (especially if there are few other sheltered areas nearby and there is a bit of a breeze).

Mid September is the peak flight season for Migrant Hawker dragonflies, which are the most likely large species to be seen in numbers (often with a few Southern Hawkers and Brown Hawkers mixed in if the feeding conditions are very good). They are also, as the name suggests, a species that is known to disperse well (or migrate) so they can occasionally turn up in numbers in areas where they aren't regularly seen - it is not unusual to find large numbers of them suddenly appear on the coast, perhaps after arriving from the continent. Darters are also often seen in numbers, but tend to be more easily over looked as they spend far more time 'perched'

The numbers seen by your neighbour may well have been exaggerated (which is human nature when reporting this type of sighting), but it would not surprise me at all to see a hundred, or even a few hundred, dragonflies in a relatively small area. For example, at Rainham Marshes RSPB reserve over the weekend there were Migrant Hawkers pretty much everywhere (probably well over 1000 all told), as well as a few hundred individuals of other species.

babu1's picture

Thanks

Lots of interesting info. I was a bit sceptical of neighbour's story, but can now tell him what was going on.
Re date; bit of a divvy moment there. I heard the story on 29th Aug 2012, so the event was a week before.
Must be a bit mindblowing to see dragonflies swarming. Just one or two is spectacular!
Have just checked an OS map and see that a small river is about one and a half miles away, not far for hawkers. And, of course, the wet spring/early summer may have produced the dewpond. Also, the coast is only 9 or10 miles away.
Well, I've sure learned a lot from this.

S Tomkins