Rainieria calceata
Identification: Legs: All femorae black at base.
Images: There are many images of this species on various sites. The Flickr site of Nikola Rahmé features a video and shows details of the pronounced proboscis, Steve Falk's Flickr has a collection, both detail the habitat.
A blog by Matthew (in Polish) is of interest for his behavioural observations, there are also many images on the Russian MacroID site and some on Diptera.info
Distribution
Europe: Countries (published), online at Fauna Europaea, Occurrences, points on abiotic (Sumner, 2018) and at GBIF
UK: Recording Scheme map of occurrences 2016 , 2018 (verified.) Online (NBN Atlas) via Easy maps or Interactive Atlas
France: Example of different methods of depicting distribution in France. occurrences predominantly from Phil Withers. One of Phil's records is a matter of a few kilometers away from the Spanish border - a challenge for Spanish photographers to obtain a country first.
In his blog Matthew (Poland, Olsztyn), posting several photographs of Rainieria calceata, provides detailed accounts of observations he has made:
(Translation from the original Polish):
“In addition, I also noticed they loved waving his front legs. Why? I am not sure, but I suspect that this may be related to the communication between individuals.
Once I was able to observe the scene, when one żółciaku (male?) met two females. First, they seemed to replace the “attentions” waving to each other front legs. After a while, however, they ran out of politeness. One chased the other, and proceeded to consume. It was a small number, the type of scene that I was able to observe. Individuals Rainieria calceata, feed mostly alone but sometimes they are also in larger groups. When that happens, they are to each other fairly quiet and usually do not interfere with each other. It is also possible that the flapping feet, can serve spoofing wasps of the family gąsienicznikowatych (Ichneumonidae). One must admit that as you look at it from the top, it’s actually like them (the more that gąsieniczników antennae, often look like the first pair of legs of the flies). Of course these considerations, it is only my own theories on the subject. Nowhere because I have not found an official, unequivocal explanation of this phenomenon, so for now, this issue remains unresolved.” (web translation of the original Polish).
Matthew has resolved the issue with his own observations, Rainieria calceata exhibits leg-waving using its two front legs both as intraspecific communication and as mimicry of Ichneumon wasps. Behaviour was also recorded by Denton, 2001, observed its similarity to ichneumon wasps, the white tarsal segments of the porrect forelegs mimicking the antennae of Ichneumons and the hind legs held straight backwards to suggest the long ovipositor. Ho additionally noted that during more active phases, the wings were waved in the manner of a sepsid.
The ability to recognise kin is cited by Bowler et al as integral component of some dispersal strategies which avoid inbreeding or kin competition.
(Denton, 2009 reports similar behaviour in Megamerina dolium).