Mystery of the Month: Mating Flies from Australia

Australian bug mating in Autumn
April 3, 2010
This pair of bugs is defying my attempts to identify them, The picture was taken in Eastern Australia south of Sydney in early autumn. There were many similar mating pairs visible. The female is 1 inch long and appears to have no wings. the male is winged but much smaller.
Bruce Terry, Sydney, Australia
Southern Highlands, NSW, Australia

Unknown Sexually Dimorphic Mating Flies from Australia

Dear Bruce,
Had your photo arrived two days earlier, our first reaction would have been that someone was playing a very good April Fool’s Day joke on us and we would have searched for evidence of photoshop tampering.  Our second thought was that this might be an accidental encounter between unrelated species, but the magnification revealed penetration barely visible under the wings of the male.  Your written account of the sighting also discounts the accidental encounter between unrelated species possibility.  These are flies, and there are species of flies that are wingless, but we don’t know of a species with such pronounced sexual dimorphism in which only the female is wingless.  This may take us hours of research that we could otherwise spend answering the increasing number of letters we are beginning to receive now that spring has arrived in the northern hemisphere.  We have opted for posting without an identification, leaving it as an announcement at the top of our homepage until we get a response with a correct identification.  Karl has returned from Costa Rica and he is wonderful at internet research.  Have you any additional photos from other angles?
Back in January 2007, we posted a photo from Australia of a Wingless Fly that was identified as a female Boreoides subulatus
in the subfamily Chiromyzinae and this is probably the same subfamily, so we will be creating a new fly subcategory now that there are two postings on our site.

Dear Daniel, Thank you for your very prompt response, and for the star billing on the website!
I attach another photo (not exactly the same bug, that one had disappeared) but the same species, this time with no attendant male.
It shows more clearly the foreparts which might help with identification.
Thank you for your help with this.
Best regards
Bruce Terry

Wingless Australian Fly: subfamily Chiromyzinae

Hi again Bruce,
Thanks so much for the high quality additional photo.  This should assist any Diptera experts that view our site.

April 4, 2010
Mirth provided us with a comment, though the link did not show.  We did a web search of the information she provided, and we found this Csiro website.

4 thoughts on “Mystery of the Month: Mating Flies from Australia”

  1. Hi!
    I´ve found this link:

    where you can read this sentence:
    “The elongate, soft-bodied Chiromyzinae, including Boreoides which has apterous females, are not uncommon in the south-east, especially in higher country”

    Hope it helps…

  2. I can’t really contribute anything substantive to this discussion but I thought I would add what I did come up with. I agree that these flies almost certainly belong to the subfamily Chiromyzinae, but unfortunately most of the Australian representatives were described in the scientific literature a very long time ago, requiring the kind of research that is difficult to access. The internet provides very little useful information. The subfamily is represented in Australia by five genera; Boreoides (3 species), Chyromyza (4 species), Hylorops (2 species), Inopus (5 species) and Stenimas (1 species). I am inclined to believe that they belong to the genus Boreoides, partly because of the general similarity to B. subulatus (the only species for which photos of both sexes are available online) and partly because it is the only genus for which I could find specific reference to wingless females. They could be B. subulatus but there are enough differences to make me doubt it. B. tasmaniensis is apparently restricted to Tasmania, so that would leave B. machiliformis. However, it is just speculation on my part and closure to this mystery really does require input from an expert. Regards. K

    • Thank you so much Karl, for your continued contributions toward solving many of the mysteries that crop up in our email box.


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