Friday, August 24, 2007

Come into my larder...

The insect world is one of singular unpleasantness. Quite apart from the risks they run from being swatted or sprayed by one of us, they are under constant threat from disease, infection, other bugs or even their own species. I don't think they break legs too often, but that would be preferable to half the nasty stuff that happens to them on a regular basis.

Working in an biocontrol lab, I am surrounded by folk who take an intense delight in discovering what natural predators kill or maim insects and weeds. Normally they do this in their labs, in the field and abroad. Sometimes an insect horror show is played out at coffee time.

Last week, we were having our usual coffee time, and one of the guys opened a window that had not been opened for some time. Out cascaded a dozen or so little mud huts most of which smashed upon hitting the bookcase below. Cries of scientific delight emanated from the guys as they searched through the debris. The little huts, it transpired, were the nests of mud dauber wasps.

Nothing if not conscientious, these thread-waisted wasps build a cute little hut out of mud which will house an egg. They then scoot off in search of provisions for the egg - preferably spiders. They sting the spider with paralysing fluid rather than kill it because then it would go off, whereas a live spider will stay fresh for the time it takes for the larva to reach maturity.

When the egg hatches, out comes a hungry little larvae, snug as a bug in its hut, with dinner on tap. The guys found this spider with a larvae attached, sucking away. The spider is only about half a centimetre long, to give you an idea of scale. Normally, about twenty of them are stuffed into the hut, to provide three week's worth of meals for the growing larvae. They lie there waiting to be drained; unable to move, scream for help, chat to their fellow captives, enjoy a last meal, or negotiate with their murderer who is nothing but an upstart spoilt little oik.

Is there no revenge on the oik? Well, no insect is immune to its own predators and freeloaders, and the mud dauber larvae is no exception. If you feel for the spider, you'll be delighted to know that there are weevils which co-develop in the mud hut. Sometimes they live alongside the larvae, sometimes they feed off both the spiders and the larvae.

Once the larvae has worked its way through all the spiders, it pupates the size of the mud hut and emerges as a rather lovely wasp. It looks a bit silly with its bottom seemingly hanging by a 'thread' but the overall black and yellow look is quite stylish. These wasps are common in the south of France. I saw several deserted pupal cases around my house when I moved in. Little did I know the raw horror of what went on inside...


  1. Well, I'm glad I read that early in the morning Sara, and not late at night...

    Do they sting?

    With that dangly bit, they remind me of the helicopters that pump water from lakes etc during forest fires.

  2. Sorry - Sarah (with an 'h'!)

  3. They don't sting us... luckily!

  4. Hi

    I once had a problem with my printer.

    The printhead wouldn't reach the end of the row resulting in a scraping noise, followed by a red light.

    I thought that I was in line to buy a new printer - having previous experience of repair quotes.

    Just on the off chance, I dismantled it and found 4 of the clay egg shells at one end. They were stopping the carriage reaching that end, hence the jamming.

    Now I know what they were.


  5. I had a go at three or four "huts" under my auvent...damn hard to knock off, and my four footed hairy friend very interested in the furious string-bum-attached wasps buzzing round my ears, whilst I hung on like mad to the steps I had climbed on and the broom handle I was using.

    Very pleased to have got rid of that - a few weeks later they had built it all again!

    And then I discovered that they also hide in the draining holes below each fitted window frame!

    Can't win.


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