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Questions about dragonfly bevaviour

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Offline glennie

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« on: October 05, 2008, 17:44 PM »
1. Why do they spend so much time around water? Is is simply because that is the most likely place to find a mate?
2. What is the reason for them going tandem above the water? (See bottom row of photos on this site:
http://images.google.com/imgres?imgurl=http://thumb1.webshots.net/t/28/29/3/88/45/2675388450037589621elJHgM_th.jpg&imgrefurl=http://outdoors.webshots.com/album/382802315ODtogT&h=75&w=100&sz=3&hl=en&start=14&sig2=gDhl19HO2_JpYvOTTXSdoA&um=1&usg=__Mr5t9Bp-SHc7VDhWWX5zs857-ag=&tbnid=cpWGcp-KjvfkmM:&tbnh=62&tbnw=82&ei=vN_oSKriC4u60gXg_-2cCw&prev=/images%3Fq%3Ddragonfly%2Btandem%26um%3D1%26hl%3Den%26rls%3Dcom.microsoft:en-US:%26rlz%3D1I7GGIH%26sa%3DN)
And when they are in tandem, why do they keep swooping down to the water so that the one at the back (female?) can dip its 'tail' into the water?
« Last Edit: October 05, 2008, 17:47 PM by glennie »

Offline parthenope

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« Reply #1 on: October 05, 2008, 19:19 PM »
Hi Glennie,

That's a fair few questions in one go!

Dragonflies spend a lot of time around water for a couple of reasons. Firstly as you probably know the biggest chunk of their lifecycle is spent as an aquatic larva (nymph). For example an Emperor Dragonfly may spend up to 2 years as an aquatic nymph followed by only 6 weeks tops as a flying adult. So water is a vital part of the dragonflly's lifecycle, the winged adults are really only a means of dispersal, allowing the potential to colonize new sites over large distances.
Secondly when the flying adult emerges from the aquatic stage it will be seen by the water initially. Once it has completed it's emergence (a process that may take two to three hours) it makes it's maiden flight away from the water. After feeding up and maturing for 4 or 5 days they will seek out a suitable wetland habitat. Once there the males stake out a territory which in some species is fiercely defended. It's all about the individual ensuring he/she passes on it's genes! In order to achieve this the males are at the territory all the time defending it and grabbing any passing female to mate with!They do this until they are no longer fit enough to hold the territory by which time they tend to have battered wings and perhaps are easy prey for predators like birds.

In some species males remain in tandem after mating so that when the female is egg laying he is still attached. In that way he ensures that only his sperm will fertilize the females eggs right up until the point the egg is laid. If he didn't stay attached in tandem after mating there is a chance that another male would get to the female before she laid her eggs, and dragonflies being the incredible creatures they are have evolved so that when copulating a male can remove another males sperm as part of the process! But if he stays attached in tandem, as you have observed, there is no danger of that! Not all species lay eggs in tandem, in some species the male hovers near by, guarding the female as she lays (oviposits). Others just don't don't bother at all!

The reason some species that oviposit in tandem fly along above the water surface with a swinging motion is so that the female's abdomen dips through the water surface and randomly washes the eggs off. Job done! Some species that oviposit in tandem actually land on a plant stem and back down it slowly so that the female becomes totally submerged as she places her eggs carefully into the plant tissue with the male there to help get her back out of the water. There are lots of variations of egg laying strategies across many different species.

So as you can see being near the water is a vital part of the dragonfly's life, and mine for that mater! I don't think I could survive without my fix of these fantastic aerial jewels.

A bit long winded I know, but I hope that helps.
Regards
Steve       

PS Check out the dragonfly pages on Clive & Sue's excellent Wildside Holidays website   
         http://www.wildsideholidays.com/natural/insects-and-creepy-crawlies/97-dragonflies.html
« Last Edit: October 05, 2008, 19:25 PM by parthenope »
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Offline glennie

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« Reply #2 on: October 05, 2008, 21:19 PM »
Fantastic Steve.
Long winded? Not a bit of it. Informative and lucid.
Many thanks

Just one doubt.
If I've got it right, it is the female on the back of the tandem as she is being swooped down to trail off eggs.

However, you write:
If he didn't stay attached in tandem after mating there is a chance that another male would get to the female before she laid her eggs,

If she is on the back, and her genital organs are at the end of her abdomen, what is to stop a second male attaching himself to the female while the poor first male briefly pulls both along? I think I might actually have seen a second male trying to do that today.

As you can see, I am taking this very seriously.  :)

« Last Edit: October 05, 2008, 21:26 PM by glennie »

Offline parthenope

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« Reply #3 on: October 05, 2008, 21:33 PM »
Glad to be of help Glennie

Here in Cornwall as we roll into autumn dragonfly behaviour does take a slightly different direction. The darters all start to congregate in little pockets of shelter/sun traps. The need to pass on their genes perhaps taking a back seat to the need to survive another day as the season swiftly brings in the cold, wind & rain!

Steve
« Last Edit: October 16, 2008, 22:37 PM by parthenope »
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Offline glennie

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« Reply #4 on: October 05, 2008, 21:39 PM »
Did you notice that doubt I had Steve?

(Poor darters.)

Offline parthenope

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« Reply #5 on: October 05, 2008, 22:26 PM »
Hi Glennie,

Sorry I missed that bit. Good point, however to actually mate the male has to get the tip of the female's abdomen almost up under his thorax so that the two form what is known as the wheel. Although the attached photos shows a pair of Scarce Blue-tailed Damselflies - Ischnura pumilio, it's the same position for dragonflies. The transfer of sperm takes place from the males secondary genitalia (on the underside of the abdomen, very close to the thorax) rather than the tip of the abdomen which the male just uses to grab the female! It would be difficult for two males to grab the female behind the head (on the pronotum) at the same time. That being the case getting into the wheel position would be very difficult to do if an original partner was already in tandem, therefore a threesome is unlikely. I say unlikely, but I have seen it happen on occasion (as you have), there are no guarantees for any strategy!
It usually works, but not always.
Well spotted, I can see your becoming a bit of a dragonfly buff! Do you think I've got away with that one?!
Regards
Steve
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Offline tonyninfas

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« Reply #6 on: October 06, 2008, 09:32 AM »
Hi Steve
You have raised one point for me in your reply ?
What exactly is the difference between a dragonfly and a damselfly ?
Tony

Offline lucy

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« Reply #7 on: October 06, 2008, 09:45 AM »
Hi Steve, Thanks for the excellent explanations.  Yesterday I saw lots of Common darters, mainly yellow - they're the females, aren't they?  They were all perched on tips of plant stems.  Would these be dragonflies still maturing in their first days (considering how far they were from any water)?

Offline glennie

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« Reply #8 on: October 06, 2008, 11:53 AM »
Thanks once again Steve.

Great to have you helping so much in this section. As you can see, your enthusiasm is catching.  :)

Offline glennie

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« Reply #9 on: October 06, 2008, 17:02 PM »
By the way, the male of the pair I saw had a very red abdomen.

Red darter? Does the darter tandem?

Offline parthenope

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« Reply #10 on: October 06, 2008, 20:34 PM »
Hi Tony, Lucy, Glennie,

The most obvious difference between dragonflies & damselflies is that mature adult dragonflies hold their wings out to the side at 90 degrees to their thorax when at rest, damselflies generally hold their wings together over their abdomen when at rest. I say generally, because there are exceptions such as the Spreadwing (formerly known as Emeralds) damselflies (Lestes species) which hold their wings out at 45 degrees to the abdomen when at rest! Dragonflies are also generally larger than damselflies. Hope that helps Tony.

Lucy your yellow/buff coloured darters are quite possibly females, but they may also be immature insects that have yet to gain their full colours, at which stage unfortunately colour is not always a good guide to sex (you have to look at the structures at either end of the abdomen to be accurate). As you suggest the dragonflies that are well away from water are usually concentrating on feeding up and maturing.

Glennie unfortunately their are several darter species that occur on the Iberian peninsula where the male is red, so it would be difficult to ID it from that alone, and most of them will oviposit in tandem so sadly that doesn't narrow it down either!

That's the first chapter of my book on Iberian Dragonflies done!!! 8)     
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Offline lucy

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« Reply #11 on: October 06, 2008, 23:47 PM »
Can you tell the sex from the end of the abdomen alone?

Offline glennie

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« Reply #12 on: October 07, 2008, 08:29 AM »
Thanks again Steve.  :)

Offline nick

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« Reply #13 on: October 07, 2008, 12:21 PM »
Clive and Sue  have this excellent overview of Iberian dragonflies and all the things they get up to.

http://www.wildsideholidays.com/natural/insects-and-creepy-crawlies/97-dragonflies/302-a-description-of-iberian-dragonflies.html

PS
Clive, I can't see this on IE 6.0 only Mozilla
« Last Edit: October 07, 2008, 13:03 PM by nick »
Nick
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Offline Clive

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« Reply #14 on: October 07, 2008, 13:36 PM »
Cheers Nick, I think I fixed it for ie 6....

Steve provided that excellent article describing these beautiful creatures and we are also working on more articles for Wildside Holidays nature pages plus a dedicated website for him to display his excellent images and observations of the nature in his part of the words as well as nature studies from his travels...
« Last Edit: October 07, 2008, 13:39 PM by Clive »
Explore the nature of Iberia at www.wildsideholidays.com

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Offline parthenope

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« Reply #15 on: October 07, 2008, 19:55 PM »
Hi Lucy,

Yes you can sex a dragonfly from the end of the abdomen alone, but it's easier from a side view! Your's is a male Darter species. Males have a small appendage (that the female doesn't have) under the abdomen at the other end (where the tip of the female's abdomen is on the photo of the Scarce Blue-tailed Damselflies in the wheel position that I posted earlier in this thread - the female is the lower of the two), which also helps.

Thanks for the plug Clive, and for all the effort you've put into helping develop a website for me. Even in it's fledgling state it was at the front of the list on a number of Google searches that I tried as an experiment. Top man! :clapping:   :clapping:   :clapping:

Regards
Steve
Cornish Nature, a work in progress
Dragonflies, images and studies of nature from near and afar
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Offline Clive

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« Reply #16 on: October 07, 2008, 20:18 PM »
Alas those google rankings will disappear when we scrap that image gallery system and replace it  :)
Explore the nature of Iberia at www.wildsideholidays.com

The beautiful town of Ronda, the City of Dreams?

The spectacular Caminito del Rey, El Chorro and Guadalhorce reservoirs El Camino del Rey

Offline harryabbott

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« Reply #17 on: October 21, 2008, 22:46 PM »
Hi guys,
A few weeks ago we had thousands of red darters migrating across our garden, near Mijas in Andalucia, they were heading directly west. This went on during the whole day , constant waves of darters so there were literally many thousands passing through. We eventually caught one and photographed it ,see attachments
My question is do we know where they were migrating to and is this a common and regular thing?
Many thanks,
Harry

Offline parthenope

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« Reply #18 on: October 21, 2008, 23:33 PM »
Hi Harry,

Welcome to the forum. I'm a bit envious to read about the thousands of Red Veined Darters passing through your garden as here in Cornwall the dragonfly season is definitely winding down.

It is not fully understood why dragonflies migrate, it certainly isn't a similar situation to birds as there is no return journey for an adult dragonfly.
It may be that when there is a large emergence of a particular species in a localised area there is increased competition in that habitat which perhaps prompts a greater need for dispersal to colonize new areas. It may be that you are seeing a concentrated stream of dragons on the move because you are relatively close to the source and it is not unknown for dragons to move in a "swarm"? Yours may even have crossed the Mediterranean from North Africa.

There is a theory that the Four Spot Chaser - Libellula quadrimaculata is affected by the parasites of a trematode worm which infects the dragonfly larvae before being passed on to the flying adult. The parasite prompts a reaction in the dragonfly which prompts it (and others) to take to the air. This then attracts the attention of birds which prey on the dragonflies and at that stage the parasite has reached it's preferred host! In rough terms that's the theory anyway!

But yes, many dragonfly species "migrate" on a regular basis and it is a very common occurrence for Red Veined Darters to do so, but other than saying they do it to colonize new areas it's difficult to say why for sure. Red Veined Darters make it to Cornwall annually, perhaps originating from southern France or the Iberian peninsula, and have bred here with increasingly regularity.

Interesting to see a dragonfly at the bottom of glass, that's my sort of drink!

Hope that helps
Steve

« Last Edit: October 21, 2008, 23:36 PM by parthenope »
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Offline Jill

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« Reply #19 on: October 23, 2008, 23:04 PM »
Despite the fact that there are no fresh water streams or ponds in the area, there are always lots of red-darter dragonflies in La Manga in September and October. They focus around the shallow pools left over after the thunderstorms, and I have seen them breeding and laying their eggs in these very seasonal bodies of water.

The thing that has always puzzled me is why they do it?

The pools dry up between the rainstorms, and they will be gone altogether by November. They might be back again in February or March, but then they will dry up again until the next autumn.
Are these dragonflies wasting their time and eggs, or have they developed some kind of clever life-cycle which deals with this problem?

Jill