This specimen of Carabus intricatus (Linnaeus, 1761) raised and lowered the abdomen alternating and spread the cerci (?). There was no other specimen present. It was in the natural environment, in 2016-05-21 in the evening, Germany, Bavaria. I noticed this about a quarter of an hour.
Dear Rudi and Rinaldo,
these appendages are unique to female beetles and very prominent in ground beetles. If a pheromone was released, you could not have noticed. However, up to now no sex pheromone is known for ground beetles although it supposedly should exist.
In the past I have also seen female ground beetles with extracted genitalia as seen in your photos after an interrupted copula or if the specimens underwent pressure. So there may actually be different explanations ...
Best,
Fabian
I cannot see, if this is a female. I thought, some specialist can see it from the annexes of the abdomen. In Carabidae, the first pair of legs is different in male and female. I cannot say it for sure, but the thickness of the first pair of legs tends to female.
Dear Rudi,
these structures are not cerci but part of the female genitalia and the ovipositor apparatus. I expect this behaviour to be part of the ovipositioning behaviour - the season would be correct as Carabus lay their eggs after a first period of activity in spring around May to June. The Larvae developp through June, July and August and new beetles hatch in fall.
Best,
Fabian
Thank you very much, Fabian, for your quick, precise and exhaustive answer!
Best,
Rudi
That was also my first impression. I couldn't see any signs of eggs already laid, but perhaps she was preparing the apparati using for egg-laying, perhaps (again) it is analogous to a human female's early labor as the dilation process progresses.
A female carabid beetle preparing to lay its eggs. In Edmonton, Alberta, Canada i have in my back yard a different carabid beetle behaving like this in early May, after emerging from hibernal diapause. A very good example of digital macrophotography to document the fleeting life cycle behaviour. The whole episode does not last very long.
Thank you all for your answers!
I did not see any egg, although I was watching the animal for a long time. It was moving all the time and did stop only sometimes for a few seconds. So it was not so easy to take this pictures.
Dear Rudolf,
I am unable to explain the observed behaviour. However, I can add that the two very evident and sclerotized structures at the end of the female abdomen are considered and called (in Italian and French texts on morphology and systematics of ground beetles), 'gonapophyses' or also 'styli'. Even just looking at the first photo, furthermore, it is clear that this specimen is a female, because the tarsi of prothoracic legs are thin, very different from male prothoracic tarsi: in the genus Carabus (sensu lato), as well as in very many other genera of ground beetles, the first pair of male legs exhibit large tarsomeres, clearly dilated.
Is the behaviour observed by you, maybe, related with the release of volatile chemicals, of pheromones?
Regards,
Rinaldo
Dear Rinaldo,
yes, this behaviour was observed (and photographed) by me and no, there were no pheromones or s.th. like that released.
I had looked up several books and the internet and could not find the name and meaning of these appendices. Thank you for the explanation.
Best,
Rudolf
Dear Rudi and Rinaldo,
these appendages are unique to female beetles and very prominent in ground beetles. If a pheromone was released, you could not have noticed. However, up to now no sex pheromone is known for ground beetles although it supposedly should exist.
In the past I have also seen female ground beetles with extracted genitalia as seen in your photos after an interrupted copula or if the specimens underwent pressure. So there may actually be different explanations ...
Best,
Fabian
I have to recall the situation exactly, perhaps I find a possible source of a carabid pheromone :)
It's easier to tell if pheromones are being emitted in some creatures than others. For instance, with the large Saturniid moth females, you can see the tip of the abdomen opening and closing. You can't sense the pheromone but you can see this. Of course the male will sense from a very great distance.
I have observed this kind of behavior in many different Coleoptera, as far I recall - Carabidae, Scarabaeidae s.l., Elateridae, Tenebrionidae etc. Moreover it appear both in males and females in a similar way - partial or complete exposure of genitalia. But I cannot exactly answer the question, just to put some additional observations on same topic.
Dear question followers,
I remember important and remarcable details:
The beetle followed me up! It moved always towards me. If I moved, it changed its direction. It was so remarcable that I called my wife to demonstrate it (She said it is "stalking" me). I stopped and it moved upon my trousers. Here it was quiet (and did not expose the genitalia, as you can see on the photos I took (attached). It was near our house.
Furthermore, it was not in the evening, but in the afternoon. I had a look at my pictures, the first I took at 3:09 p.m., the last at 3:35 p.m., the behaviour of exposing the genitalia lasted on.
Now in November, there were on two different days two specimens of Carabus intricatus in our house (one at a time) on a place, where I never had animals from outdoor. The second one was last week, where there was already frost outside, so that I waited a day to release it in the garden.
So the carabid pheromone was much nearer than I expected?
Any suggestions?
Best wishes,
Rudolf
Maybe your snail perfume was so tempting, this Carabus couldn't resist... :)
I asked Thierry Deuve about the observed behavior, and he confirmed that it has not yet been proved that Carabus are able to produce pheromons. However it may not be impossible, as some structures near the genitalia that could have this function have not been studied in detail yet.
I can only repeat what I wrote earlier - I rather would not expect a pheromone to be involved in this. All glands in this section of the body of carabid beetles have been extracted in the past and no candidate was found (other than in Elateridae or Scarabaeidae).
For your recent observation: Some carabid beetles are also active during the cold season and in the case of C. intricatus (which actually is quite common in your region) I know that specimens are often attracted to buildings due to milder climate in their vicinity.
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