Saturday, May 16, 2009

Wall Butterfly Behaviour










I’ve been watching wall butterflies lately, and their behaviour is fascinating. Have you noticed how, when they land, they fold their wings and shuffle around until their vertical wings are exactly parallel with the sun's rays – like the butterfly in the bottom photograph? I used to think this was some kind of defensive behaviour, so that their well camouflaged wings and body cast the smallest possible shadow. It's certainly easy to lose sight of them when they do this and if you look away they're hard to spot with their wings folded. But now I'm not so sure - I think the reason for this might be more subtle. When they orientate themselves like this it means that when they open their wings (see middle photograph) to bask their wings are at right angles to the incoming sunshine and so are perfectly positioned for absorbing the maximum amount of solar radiation. Maybe this is dual purpose behaviour and there's a grain of truth in both theories. I imagine the butterfly can tell, after it first lands, when its wings are aligned perfectly parallel to the sun’s rays because then neither eye would be shaded by the wings. They do seem to be very aggressive butterflies. The males that I’ve been watching patrol a well-worn footpath beside a hedge, engaging in brief aerial dogfights with rival males before seeing them off the premises. Courtship is an elaborate affair too. When a female arrives on the scene she indulges in a lot of wing vibrating, which I guess might be to drive off the volatile come-hither chemicals called pheromones that butterflies are known to use to attract a mate. The male flies around her and lands facing her, both insects with their wings outstretched, and them he seems to head-butt her and contact between their antennae takes place. Then I accidentally scared them both off (top photograph), so I don’t know what happened next................(the male is the settled butterfly on the right, with the broader diagonal dark brown stripe on the forewings)

4 comments:

  1. Interesting observations on their behaviour.
    I'd love to see one; the markings on the underside of the last picture are so intricate. A real beauty.

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  2. Not seen this variety but have noticed that some other butterflies move round to a particular position when resting on the ground. ext time I see one I will have to take notice of its final orientation.
    Beautiful close shots.

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  3. Hi John, I think there's a really interesting world of insect behaviour out there to explore, in butterflies and less colourful insects. I bought myself a close-focussig Minox Macroscope which I'm hoping to use for this (see http://www.optics4birding.com/minox-minoscope-8x25-review.aspx)

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  4. That looks an interesting bit of kit, nice and compact to carry around. Always good to see a favourable review. I always try to find reviews before getting a new piece of kit as, according to any manufacturer all their equipment is the best thing since sliced bread.
    I've been experimenting to see how close I can get to things with the camcorder. Once it dawned on me that I had to use the wide angle setting it was surprising just how close it would still focus. All I have to do now is find a suitable subject to try it out on :>)

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