Tag Archives: insects

natural history, science

Nature’s Legs

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A few days ago I spotted a mosquito on the bathroom wall. Now we’ve all seen mosquitos before but on this occasion I was fascinated by it’s size and anatomy – especially its incredible legs; thin as the finest silk thread.

Culex mosquito
Culex mosquito

How does Nature make such structures – and make them functional? Scientist though I am, it baffles my brain and I can quite see why some people believe in “intelligent design”.

Surely those legs cannot be anything more than stiff supports. Insects have an exoskeleton in contrast to our endoskeleton. The legs need nerves, muscles and circulation to make then more than fixed supports. Legs can move, allowing their owner to walk, clean itself, and even jump. The muscles have to attach to the inside of the exoskeleton, and there have to be nerves – and a method of supplying energy – to trigger them into action.

Insect circulation doesn’t work the way ours does as they do not have hearts: basically they use haemolymph which can diffuse around their small bodies, or be pumped by, for instance, muscular membranes. Some insects use this as a system of hydraulics, in combination with the muscles, to move legs etc. – apparently muscles to move a joint one way, and hydraulics for the reverse. All of which must be under some form of nerve control – and they don’t have that many nerves running from their tiny brains.

Even more weirdly, some insects (eg. jumping spiders, plant hoppers) have a system of gears which work their legs. Crazy or what?

two rice brown plant hoppers
Rice brown planthopper

Just how can these structures be created? You would think they’re so tiny they cannot be even one cell thick – but they have to be many, many cells thick. Which just goes to show how tiny our cells are.

I know evolution has had billions of years to achieve its designs, but I still struggle with how any living thing works or has evolved. Yes, I know the theories, and I can understand it as abstract pieces of mechanics and chemistry. However I really struggle coming to terms with how it all evolved, how it all works – together – and the sheer complexity of living organisms. When you think about it, it really shouldn’t be possible.

environment, natural history

Asian Hornet Warning

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People in the UK, and especially the South-East, are asked to be especially alert for the presence of yellow-legged Asian Hornets (Vespa velutina), following a record number of sightings last year.

These hornets are invasive and a major predator of honeybees. They’re slightly smaller than our native European Hornet (Vespa crabo) but about twice the size of a common wasp or honeybee (see below). Over the last decade or so they’ve spread across mainland Europe from an original accidental introduction in the south of France.

Hornet and wasp size comparison
[click the image for a larger view]

As the graphic shows, the Asian Hornets are dark coloured, with a broad yellow/orange band across the fourth abdominal section, and yellow lower legs. I’ve only ever seen a mounted display specimen but I was struck by the dark colour. By contrast European Hornets are slightly larger, more likely to be brown rather than black, with much more yellow on their abdomen and dark legs; they look more like an oversized common wasp.

Unless their nest is disturbed, Asian Hornets are not normally aggressive to people. However they are prolific and invasive; which with their ability to predate honeybees and wipe out complete hives, makes them a serious pest. They find beehives and pick off the workers as they come and go; I’ve seen it estimated that a single Asian Hornet can catch and kill 50 honeybees a day! They have few, if any, natural predators in Europe.

If you think you’ve seen one, you must report it via the Asian Hornet Wasp app (available for both Apple and Android smartphones) or online via the UK CEH Non-Native Species Alert website. If possible try to get a photograph of the insect. If you can safely capture the offender so much the better – emphasis on your safety. But please do not go killing any captured insect unless you are very sure you have an Asian Hornet.

Note that these are not the so-called “Murder Hornets”, the Asian Giant Hornet (Vespa mandarinia), which have recently invaded the NW USA. Vespa mandarinia are larger, even more alien-looking, equally as predatory and much more aggressive.

Find more on Vespa velutina at:
Defra Asian Hornet Sightings page
NNSS Alerts page
EU LIFE Programme
Wikipedia.