Diptera.info - Articles: Observations on Medetera jacula (Fallén, 1823)

Courtship
The first step of courtship is the male's "wing helicoptering". The wing helicoptering point is to the left or right side (+/- 45 degree) of the object of courtship, at a distance of 1-3 cm. Wing helicoptering is not a nessesary step; it was rare in early August and much more frequent in early September. It takes 2-6 sec.

Then Medetera jumps into blind sector of another Medetera. It is the position for the second step of Medetera's courting. The second step consists of tender stroking of scutellum and wings of the upper fly by one of the forelegs of the lower fly (fig. 11), then less tender stroking done by both forelegs (fig. 12), then mating (or mating attempt) (figs. 13-1, 13-2).

Copulation is short and takes 10-25 sec. Being aware of mating habits of related Empididae family, I was not very surprised to discover that neither female feeding disturbs male mating, nor male mating disturbs female feeding (fig. 14).
As you, of course, noticed there is one problem: the lower Medetera is always a male, but the upper one is in most cases male too!
I imagine, that for male far vision, the tree-trunk landscape with the vague silhouette of another Medetera looks like that shown in Figure 15.

Surely, Medetera recognizes the silhouette of another Medetera, otherwise Medetera is almost invisible on the bark even for more sharp eyes than Medetera's far vision. To prove that I attached small paper "pseudomedetera" to tree surface (fig. 16) and this pseudomedetera was the object of a full courtship program with wing helicoptering and stroking. I also observed natural misrecognizing: a male courting a tree bark tooth once, another time courting a small Medetera pallipes. So, male mating strategy may be formulated as follows: "I'll do my best and I don't much care whether the female refuses mating with me because she is not ready to or because she is a male or because it isn't fly at all."
But it still does not explain why the fly in the upper position is male in 8 cases out of 10. I have two guesses. First guess is that males have to do their best to find more silhouettes of other Medetera on the trunk. It does not matter what exactly is being done for best searching (for example, to choose higher points for observation or to change points more often), but searching male itself becomes a better visible silhouette for other males which immediately come to try to mate with him. The second guess is connected with the first one: mating attempt catalyzes reciprocal mating attempt. I observed a comical scene. Male N1 sits on a bark, Male N2 jumps to him in the lower position and begins to stroke him. Being a male with traditional sexual orientation, Male N1 finally jumps out. But after that, Male N1 can see the silhouette of another Medetera (it is Male N2). Male N1 jumps to him in lower position and begin to stroke Male N2...
Medetera, these raptors of tree bark, are peaceful towards each other and do not show any territorial behavior.

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#11 | Petr Michael on 28 October 2009 10:15:39

I have never read and seen anything else as for a fly
behaviour.

#12 | Keith Short on 11 September 2014 21:01:53

Nikita,

I am interested in rearing some dolis, especially Condylostylus species. Have you ever tried to raise eggs layed by squeezing the female's abdomen? I have had no luck searching for the larvae.

Thanks

Keith

#13 | Nikita Vikhrev on 27 October 2014 13:49:11

Dear Keith, excuse my long overlooking your question.
I had never deal with rearing, so I have no experience. Concerning Medetera I wondered why I had never seen egg laying. The presence of eggs inside females confirmed my suspicion that "hunting trees" and "ovipositing trees" are not the same. What the requirments is for atree to be "ovipositing" one - I do not know...
Best wishes,
Nikita

#14 | Paul Beuk on 30 October 2014 11:00:52

I once reared two Medetera from dead pine on which I also found Zabrachia (Stratiomyidae). The microclimate on a dead tree may be different than that on a living one and thus attract other organisms on the outside surface of the bark. So, while the dead tree may be interesting for larval development, it may not be so for adults to hunt on.

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