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  1. #121
    Administrator gavin's Avatar
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    Quote Originally Posted by Mellifera Crofter View Post
    Do you know, or can you guess, why this hover fly tries to mimic honey bee drones, Gavin?
    Kitta
    The guess would be that a syrphid looking like a honeybee ends up looking like a drone, as drones are fly-like. Probably that's good enough to get some protection.

    Drone flies even vary, like honeybee workers, for an orangey band on the first abdominal segment.

  2. #122
    Senior Member fatshark's Avatar
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    Quote Originally Posted by gavin View Post
    Drone flies even vary, like honeybee workers, for an orangey band on the first abdominal segment.
    But these yellowish Italian drone flies are disliked by some who prefer the near-black drone flies. I can't find the original images now but I think they were good enough to check the discoidal shift …

    And seriously … from "http://eprints.nottingham.ac.uk/96/1/ImperfectMimicry.pdf"

    Diptera are exclusively mimics of Hymenoptera, and most of the mimics belong to one family, the hoverflies (Syrphidae). This is one of the largest and most diverse of all dipteran familes, with a worldwide distribution and more than 5600 species described (see Rotheray, 1993; Rotheray & Gilbert, 1999). The literature contains information about the mimetic status of some 279 species of hoverfly (Gilbert, in prep), an astonishingly high number relative to other insect groups: clearly mimicry is a dominant theme of the evolution of this group of flies. Especially in Europe, most of the models for hoverfly mimics appear to be social insects: the bumblebees, honeybees and social wasps.

    And there's pages and pages more if you're interested.

    Remember that the mimicry is not so that the syrphid resembles a bee to us … it has to resemble a bee to whatever preys on syrphids (presumably birds). In the paper quoted above they cite work in which mimicry is tested in terms of what a pigeon sees …

    An obvious objection to the claim of differences in the specificity of mimicry is that human perception is not the same as that of predatory birds, and perhaps they perceive the ‘poor’ mimics differently. Dittrich et al. (1993) used operant conditioning to test whether a representative bird would make the same sort of mistakes that humans do when presented with models and their hoverfly mimics. They chose pigeons (Columba livia) to represent a generalized avian visual system. The birds were trained to discriminate between images of wasps and non-mimetic flies, and then tested to see how they would respond to images of wasp mimics. One group (fly+) were trained to peck at the images of non-mimetic flies for food, wasp images being unrewarded. A second group (wasp+) were trained to peck at wasp images for food, with the non-mimetic flies being unrewarded. Both the fly+ and wasp+ groups of pigeons learned to discriminate between the two sets of images equally quickly, after only two training sessions. During the 20-sec projection time of a rewarding stimulus, the pigeons pecked 50 to 60 times, whereas they hardly pecked at all at non- rewarding images. This suggests that there is no inherent bias of the pigeon visual system against black-and-yellow wasp-like patterns (perhaps not surprising, since it is not insectivorous).
    The pigeons were then tested using images of hoverflies chosen to represent a range of mimetic quality as perceived by humans. The pigeons were extremely consistent in their responses, ranking the hoverflies in more or less the same order as did the humans, with the fly+ group being more or less the mirror image of the wasp+ group. Pigeons do appear to see hoverfly mimics in roughly the same way as we do: they seem to rank the images in the same way, and make the same sort of category mistakes.
    Last edited by fatshark; 16-06-2014 at 08:38 PM. Reason: Missed a bit

  3. #123
    Administrator gavin's Avatar
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    So, in the main, we're as good entomologists as pigeons? Even though pigeons don't eat them (whearas we sometimes do).

    It strikes me as cruel to train pigeons to peck at wasps. Unless these pigeons will never see the great outdoors, destined to be a Friday evening snack for the cruel scientists taking their work home with them. Do scientists do that?!

    Back to the colour morphs of the drone fly. Doesn't that (the existence of a proportion with an orange band) suggest that the original Amm was a bit more diverse in colouring than current fads would suggest? Indeed, didn't Beo Cooper say that, or was it Ruttner?

    This time we've discussed drone flies I've managed to avoid linking to the bizarre medical tales of rat tailed maggots (their larvae) being found colonising humans. Yuck. Maybe they get closer to man than pigeon sometimes.

  4. #124
    Senior Member fatshark's Avatar
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    I don't think scientists ever take their work home with them …

    Re. the pigeons thing. There was something else in that paper (which I found after a quick Google, having remembered how much I enjoyed an evolution course many, many years ago) which said that in tests of animals being stung by bees/wasps, birds were rarely stung. I began to wonder if this means that whatever is predating syrphids is something other birds.

    I'd prefer not to hear your rat tailed maggot stories … however, I did read an excellent article on insects being used for warfare. Did you know that before the cannon was invented ships carried clay beehives to lob at the opposition? There were a load of other examples. Great material for talks!

  5. #125

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    The discussion about how this fly is mimicking a drone bee is making me feel slightly less embarrassed about thinking it was a bee in the first place. and has seem to have started somewhat of a debate i was not expecting. thanks for the responses.

    Jon, I am sure it was your Dad we bought honey from last year, my parents know them. the location is is spot on. (I am not sure on protocol whether to mention names over the open forum)
    I plan to get in touch with the mid ulster association and hope to attend some meetings over the summer.

    Mark.

  6. #126
    Administrator gavin's Avatar
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    I've known really senior beekeepers to think that they were bees, so there's no need for any embarrassment. Nice to see you posting, Mark.

  7. #127
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    I.D THIS BEASTIE PLEASE - DSC02861.jpg - can anybody id this huge beastie which was feeding yesterday on the Nepeta, along with bumblebees and honeybees. It was its sheer size that caught my attention - though unfortunately there was nothing close to it for a size comparison. Thanks if you can point me in the right direction.

  8. #128
    Administrator gavin's Avatar
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    Lovely photo, Marion. It is a narrow-bordered bee hawkmoth. The Butterfly Conservation people might like to hear about your finding in case it is in a new area - see the link.

    I thought for a minute it was a hummingbird hawk moth, a migrant which ranges far and wide, but this one is resident. We're seeing plenty of migrant butterflies (painted ladies, red admirals) here already.

    G.

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    Thanks for the i.d Gavin - it's definitely the first one I have ever seen - and I will check out the link, thank-you - what a size they are !

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    Great picture Marion

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