Friday, October 05, 2012

Trash bugs – a minute walking dustbin

My mum’s been to visit and we went for a walk together in our woods yesterday. We were identifying different trees and I handed Mum leaves from an ash, hornbeam, sweet chestnut and hazel. When we came out into the sunshine, she had a closer look and saw a scrap of dust … that moved.

Not having a magnifying glass to hand, I took a photo on the macro setting for later analysis—not easy as it kept moving. Downloaded and blown up, we were still none the wiser. We knew it was a living thing as it moved and was too small to contain batteries. Someone or something had taken a tiny little bug, spread glue all over, then emptied the contents of a miniature dustbin on top of it.

We couldn’t find it by flicking through our identification books, nor by following the keys, so tried the Internet. But what terms should I try? “Insect covered by detritus”, then “debris” and then I found it. Sometimes referred to on American sites as a “trash bug” it seems that it is a lacewing larva.

Having identified the bug and now wanting to furnish as many useful facts about the lacewing, I turn to Bugs Britannica  (by Peter Marren and Richard Mabey) and am horrified to find that the “lacewing larvae lack a functioning anus”. Whether you believe in God or evolution or both, you have to admit this is a serious oversight. Open-mouthed in astonishment, I read on, “so they store up their body waste until the moment when, after changing skin one last time, the void it all in one go. Apparently, some lacewings can be identified by the shape of this single enormous dropping.”

They are sometimes known as ‘stink-flies”, as they use this disability in aggressive fashion, excreting if handled. If your now seriously doubting this stinking-trash-bug has any endearing features, I will immediately disabuse you of that notion by saying that a single lacewing larva could consume between 1000 to 10,000 aphids during its “lifetime” before it metamorphoses.

Reckoning that one lacewing mummy and daddy might produce 300 eggs, that’s a lot of aphids that won’t be bothering your broad beans; "you do the math", as an American gardener might say.

Here’s a few of the websites that were helpful: