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Hi there,
i just returned from a long vacation in Italy and i found many many freshly mated Tetramorium queens today on a walk.

Altough i know that Tetramorium caespitum queens usually tend to fight each other, i asked myself if pleometrosis, in general, is possible with this species.

Pleometrosis means that 2 or more queens found a colony together, which doesn't necessarily mean that all queens remain in the colony. Monogyne species usually kill all queens but 1 as the colony grows bigger.
Tetramorium caespitum is a monogyne species, but so is Lasius niger, and they are also known to found in pleometrosis.

Just to clarify:
A successful pleometrosis for a monogyne species like this would be that the queens start the colony together, but the workers later choose one queen and kill the other one.

The simple question is:
Will 2 or more Tetramorium caespitum queens found a colony in pleometrosis or not?
Will they
(a).. kill each other but 1 queen which then founds a colony on her own, or
(b).. will they actively assist each other and the workers, once they eclose, kill all but 1 queen?
(c).. anything else that might be an interesting observation

I have 8 test tubes with 2 queens each.

I will keep this thread up to date with new developments and post my conclusion here once the experiment is completed.

For now, everything looks fine.
All queens sit next to each other on the wet cotton bud in their test tubes.
Last edited by nortorn on Sun Aug 07, 2016 9:59 pm, edited 2 times in total.
Well, i just checked the 8 test tubes and we still have 16 healthy queens.
They all have a batch of eggs which both queens are sitting next to. I also saw 1 queen feeding the other one.

I made another interesting observation about 2 weeks ago. I found a wild colony with 2 queens while gardening and preparing a spot for a permanent fireplace. No way they could have stayed there, so i took them in.
I have absolutely no idea if the 2 queens founded the colony together or if one of them joined in later on.
Both queens are still alive and laying eggs.
I'll keep a close eye on this colony and the founding queens to see if not only pleometrosis, which works very well so far, but also polygynie is a thing in the Tetramorium sp. E world.
We'll see.
To be continued...

The 2 queen founding experiment comes to an end as my initial question is answered.
Yes, Tetramorium caespitum (sp. E) can found in pleometrosis.
All 8 pairs of queens had their first workers in the last couple of days. I noticed in 4 test tubes, the tiny first workers became very aggressive towards 1 queen. Of course, 2 or 3 tiny nanitic workers of this species are not capable of killing a queen, but i decided to separate them anyway. As more workers are eclosing, they will have enough force to kill one queen, but that was not the point of this experiment.

This being a monogyne species, the experiment went exactly the way i expected.

There's just one little problem. I still have the colony from my garden with 2 healthy queens inside. There are close to 200 workers now and no signs of aggression.
For some reason the workers are not killing one of these queens, which means that the colony is at least facultatively polygyne (2 fertile queens, 1 laying eggs), if not completely polygyne.
I'll keep on closely observing this colony to find out whether it is truly polygyne or not.
More Updates coming...
Well, there are some news to this.

This colony, other than most of my other ants, is not hibernating.
I keep them at room temperature and there is a decent growth rate.

I am pretty sure that i can now confirm, that both queens are laying eggs.
i seperated the queens but left a way for the workers to get into both parts of the nest and there are many eggs in both parts of the nest.

I also saw both queens individually laying eggs and until now, the colony grows very good with 2 queens.
It is not twice as fast as another colony of this species that i keep for comparison, but almost.

This colony is clearly polygyne and i want to take it one step further. I´ll try to introduce even more queens next summer, we´ll see how that works out.
2000+ workers and still rising. Both queens are being fed and groomed by the workers. The amount of brood is truly stunning, at least as much as there are workers.

As if this was not interesting enough, here is another story.

I had to do some garden work again today and had to rearrange a few stones.
Under one of them i found another colony with 5 queens sitting under the warm stone. Obviously I cant say if all of them lay eggs, but they all looked quite physogastric. It seems like i am on to something.

Unfortunately, by the time i got my camera, they were all gone.
I left the stone at this location and usually the queens come back up in a day or two. Next time I'll have the camera with me.

It is of course too early to make any statements, but I think that this species is polygyne, at least in my region.
I am currently thinking about contacting a german myrmecologist to send the 2 queen colony to him so he can dissect the 2 queens under a microscope and hopefully confirm that both of them are fertile and laying eggs.
This would give the whole subject a more official and scientific touch as my efforts can at best be described as hobby research.
i seperated the queens but left a way for the workers to get into both parts of the nest and there are many eggs in both parts of the nest.

I also saw both queens individually laying eggs and until now, the colony grows very good with 2 queens.
It is not twice as fast as another colony of this species that i keep for comparison, but almost.

milant wrote:Instead of having the queens killed have you attempted to separate the queens and see if they still lay eggs? That seems like an awful lot of brood and workers awfully fast for just one queen to do

Yes, i did that.
Still, that is at best an indicator that this species might be polygyne under some circumstances, but it has no scientific value.
Short update:

Yes, the colony is definitely polygyne! Well, was.
The queens are dead, but i did it for science :D
I sent the 2 queens and a handful of workers to a german myrmecologist and he dissected the queens.

He was able to confirm that both queens were indeed mated and producing eggs.
He didn't find many yellow bodies (corpus luteum) in the ovarioles,
which means that they did not lay many eggs yet (this year) and i can confirm that when i look at the brood of the now queenless colony.
So, there is the "scientific value" finally.

He is doubtful about the ants being the "real" Tetramorium caespitum, as you may know the Tetramorium caespitum/impurum species complex is still a complicated subject.

Still, it is an amazing fact to know that this colony was truly polygyne,
because either it proves that polygyny might be a thing in the caespitum/impurum complex
(which was proven already in a paper by said myrmecologist and others; though these colonies were found in an alpine environment in Austria)...

Steiner, F. M.; Schlick Steiner, B. C.; Buschinger, A., 2003: First record
of unicolonial polygyny in Tetramorium cf. caespitum
(Hymenoptera, Formicidae). Insectes Sociaux 50(1): 98-99

By clicking on the link after "PDF Full Text" you can download the PDF.

...or that it is the species Tetramorium moravicum (another species complex), which is known to be polygyne and which can be found along the Rhine, Mosel and Lahn rivers in southern Germany, but the colonies i found outside would be the most northern reported population known.

However this turns out, it is highly interesting to possibly contribute to science and i can only encourage everybody else to work with their ants rather than "just keeping them", it makes the hobby so much more awesome.
Well, we already found out that the colony was polygyne, though, it is in fact Tetramorium impurum, not Tetramorium caespitum or any other species of this complex.
After both queens were dissected by Prof. Dr. Alfred Buschinger, they were sent to Dr. Bernhard Seifert of the Senckenberg Institute in Görlitz with a couple of workers.
It took him more than one hour per worker to identify the species, 30 characteristics have to be checked with a total of 44 measurements per worker.

Polygyny was suspected for Tetramorium impurum, but it was not confirmed.

I think, it is now safe to assume that Tetramorium impurum can in fact be polygyne. (Maybe just under specific circumstances? The nest density here is enormous, might be a way for the ants to adapt to these conditions).

I am in contact with Dr. Bernhard Seifert and will try to find him a few more samples of polygyne colonies.
2 queens from 1 colony is a small sample size when it comes to science.
More samples from wild colonies will help to confirm this result and maybe he will be able to make it official then.

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