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

Oviposition
Ovipositing habits are a mystery to me, but I think that a negative result has to be reported as well. I have often seen Medetera females with a fatty abdomen, especially at the end of August and September. Fig. 17 shows Medetera on 5x5mm paper and yellow eggs which I squeezed out of female's abdomen. The eggs are large enough that I hardly imagine I can overlook ovipositing I have been especially looking for.

Besides large eggs there is another thing to consider. Medetera female has long ovipositor, and it is rather natural to suppose that it uses this ovipositor for ovipositing. I have observed Medetera with pulled out ovipositor 3 times. Female pull ovipositor out, massaging their abdomen by hind legs (fig. 18). If female stop this massage, ovipositor begins spontaneously pull in abdomen (and it seems to me that female has not possibility to pull it out without help of legs). An undisturbed female repeated this procedure 2-5 times. Still eggs-laying has never been recorded by me.

Medetera pallipes
Medetera pallipes is the second species I found on chosen trees. This much smaller and more timid species is more difficult to observe. The scant information I have is:
1. Medetera pallipes avoids a height of less than 0,5 m;
2. Medetera pallipes also use wing stroking as courtship (fig. 19) (**see also below).

* Dolichopodidae feeding strategies
In total I have observed feeding in 5 different genera of Dolichopodidae. I have doubts that the common view of Dolichopodidae as predators which suck out their prey is really as common in Dolichopodidae.
Campsicnemus scambus was observed twice as a predator that really sucks out its prey. The prey (Collembola, Entomobryidae, Lepidocyrtinae) was large, sucking took 10 min and afterwards the empty skin of prey was discarded (fig. 20). Once it made an unsuccessful attempt to attack a large chironomid on the water surface (fig. 21).

Hydrophorus praecox was observed sucking out a large chironomid (fig. 22).
Hydrophorus borealis was observed 7 times swallowing Oligochaeta (freshwater worms) (fig. 23-1). It is amazing that for catching worms Hydrophorus borealis put its head completely under water surface!
Hydrophorus borealis detected numerous and helpless aphids on silt, but never attacked them (fig. 23-2).

Liancalus virens was observed once swallowing some worm-shaped creatures (most probably Diptera larvae) in very same manner as Hydrophorus borealis.
Dolichopus sp.(1) was observed swallowing tiny Collembola (Sminthurides penicillifer (?), Sminthurididae) along with a good amount of water and silt (fig. 24).

Recent observations of another Dolichopus sp.(2) convince me that it acts exactly as hen walking in the yard and pecking invisible small objects (fig. 25). During such feeding a large (6-7 mm) Dolichopus sp. female did not pay any attention to the adult Collembola on the same leaf.

Thus, so far Campsicnemus scambus and Hydrophorus praecox appear really to use "suck strategy", but Medetera jacula, Liancalus virens, Hydrophorus borealis, Dolichopus sp.(1) and Dolichopus sp.(2) appear to use "swallow strategy".

** Medetera truncorum
During the period 20 -15 October, 2006 I observed the Medetera truncorum on an old Platanus orientalis and stone fence around it on city park of Adler, Sochi region, Russia, for a total of 4 hours.
1. All main characters of behavior of Medetera jacula are true for M. truncorum: waiting and hunting positions; cleaning; hunting habits; swallowing of prey; courtship, including male to male (fig. 26-2); lack of ovipositing observations.
2. Wing helicoptering looks rather different: wings during helicoptering almost lay on abdomen.
3. Liquid excrements were always whitish as shows Figure 26-1 (M. jucula ? always blackish).
4. Short list consisting of 5 preys is:

Collembola, Symphypleona	1
Thysanoptera	2 (fig. 26-3)
Diptera, Cecidomyiidae?	1
Coleoptera, larvae	1

Acknowledgements
I am very grateful to Dr. Tony Irwin for his kindness to check the text (both as Dipterologist and English), his grate help in prey identification and a lot of priceless advises. I thank Dr. Igor Grichanov for his identifications of Medetera species.

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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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