Sunday, April 19, 2009

This way madness lies...







Spent a hot and frustrating afternoon chasing hyperactive bee-flies around the garden, as they visited the forget-me-knots and lady’s smock flowers around the pond. Never really got the picture I was hoping for, but made an interesting discovery - take a look at the middle picture (double-click on image for a larger version). There’s a step change in the thickness of this insect’s long, straight proboscis (see top picture) and where this step-change occurs the narrow, pointed tip splits apart into a Y-shape when it withdraws from the flower. I’m guessing that when the two halves are brought back together again this reforms a narrow tube that draws up nectar by capillarity, and that this splitting-and-reforming operation prevents the formation of airlocks in the hollow proboscis. A high shutter speed reveals what the human eye can never see, even though it means that the photos have a very shallow plane of focus.

7 comments:

  1. I know how you felt from the time I decided to try to capture a drone fly in mid hover. Well done on the photos you did get and on the discovery about the proboscis. Fascinating.

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  2. Afternoon well spent, I'd say.
    Capturing mid flight like that is some achievement, and the discovery.
    Very interesting post.

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  3. Thanks for your comments, Midmarsh John and holdingmoments. They're such elusive insects - sometimes they seemed to disappear in the fraction of a second that it took for the decision to press the shutter button to travel from my brain to my finger - I had a lot of frames with flowers but no insect when I downloaded the images.

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  4. Fascinating observation on the plumbing of the proboscis. What delicate long legs they have too - such poise when feeding.

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  5. They mostly seem to use the legs for hanging onto the flower, Rambling Rob, to gain a purchase on the petals to they can push their proboscis to the bottom of the corolla tube.

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  6. That is one amazing piece of observation! You ought to post that to the diptera.info and dipterists forum groups. I'm sure they'll be very interested. I have the Stubbs & Drake book 'British Soldierflies and their Allies' but the proboscis movement you witnessed isn't mentioned anywhere in the section on Bombyliids!!

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  7. Thanks for the advice Steve, I'll do that. I'd be interested to know more about this. Both sites look fascinating - I wasn't aware of either.

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