Tuesday, August 16, 2011

Pottering about

Whilst fiddling around in the garden the other day, I happened to lift up a large pot to see what was underneath. I was hoping to see a devil's coach-horse or a grass snake. Instead I found these...
...12 little cells made of sandy mud. I could see some, actually most, were broken or holed. But at least 3 were intact (the top 3 in this photo) and looked brighter than the rest.

Looking closer, the little cells are made of layers of mud with sand-grains. They are quite rough on the outside but the inside is perfectly smooth.

The ends are capped off and completely sealed. Clearly they are made to protect whatever is inside, sealed from the environment, be that the British weather, predators or parasites.
I guessed some kind of solitary wasp might have made these stand-a-lone little pottery cocoons, so I scampered indoors to find my insect id book. I tend to rely on Chinery (1986) for most basic insect identification. But as I didn't have the actual insect and there were no pictures of cells like these in the book, I was a bit stumped.

At first I thought possible builders might be potter or mason wasps; Eumenidae. But Eumenes coarctatus, the heathland potter wasp, is at the northern edge of its range in the UK and doesn't occur this far north (see here for UK distribution map). So my garden was the wrong habitat, in the wrong part of the country. And the shape of the cells was wrong: Eumenidae build tiny pottery vases with a lip, which I've seen on the continent. Here is a typical Eumenidae pot on Bug Guide (a North American online id guide).

So temporarily defeated, I uploaded a photo onto iSpot and sure enough an expert (in this case David Notton an authority on UK Hymenoptera from the Natural History Museum) came forward with a probable identification: Auplopus carbonarius, a spider-hunting solitary wasp. A.carbonarius is 'unique' amongst British spider-hunting wasps in building aggregations of clay/mud cells in sheltered locations (David Notton, iSpot, 2011).

Thanks to a generous band of people who share their photos online, I am able to show pictures of the adult wasps. This gorgeous picture of an adult spider-hunting wasp, A.carbonarius, was taken in Portugal. [Picture from Wikipedia taken by Joaquim Alves Gaspar in Portugal in 2007. Used under a Creative Commons Attribution/Share-Alike 3.0 Unported License.]

Spider-hunting wasps, Pompilidae, are solitary (as opposed to social) wasps who build nests (usually burrows), and provision these with fresh arachnoid meat (aka a spider) to feed their developing larvae. They capture and paralyse a spider, and drag it back to their nest, still alive and fresh. No mean feat! The wasps often amputate the legs of the paralysed spider to facilitate transport (Jeremy Early, 2011). They are ectoparasitoids; spending part of their life-cycle (in this case the larval stage) living off a host. They seal the nest up, leaving their egg to hatch and feed on the spider. End of parental duties.

This wonderful shot, showing the wasp dragging a stunned spider to one of its cells was taken in Germany. [Picture from Wikipedia taken by Fritz-Geller-Grimm, in Germany in 2006. Used under a Creative Commons Attribution/Share-Alike 2.5 Generic License.]

And below, not for the squeamish, is an Australian spider-hunting wasp dragging a rather large huntsman spider up a wall to her nest. I remember these large, long-legged spiders very well as they used to wander across my bedroom wall in Perth, Western Australia and I once put my hand on one when I pulled a curtain back......I still shudder to look at them and develop acute cutis anserina. [Picture from Wikipedia taken by Brian Jenkins, in Australia in 2009. Used under a Creative Commons Attribution 3.0 Unported License.]
Whoever built these little mud cocoons in my garden, they have some seriously impressive engineering skills. They sourced and quarried the materials, and transported them to the site under my pot, a site which they must also have selected with some care. Then they built these pottery cells in situ. They then went hunting, caught a live spider, drugged it and dragged it back to the nest. Then they stuffed it inside the cell, laid an egg on it and sealed the top off with more mud. Wow! That is some effort. I stand in awe of my waspy neighbours. 

Auplopus carbonarius is a nationally notable species. As we have no wasp vice-county recorder in Bedfordshire, the bee recorder has agreed to take this record.

I've checked under the other plant pots nearby and can't find any more invertebrate pottery. But I'm very curious, so although I won't open a cell to see what's inside, I've brought them indoors and placed them in a box. I'll have to keep the humidity right. So now it's time to sit back, watch and wait, till spring......

If anyone has any corrections, clarifications or additions to make to what I've written I'd be very happy to hear them :-)

Bibliography & Further Information
Chinery M (1986) Collins Guide to the Insects of Britain & Western Europe. Collins. IMHO the must have guide to Britain's insects.
A very informative website stocked with information about these wasps (and many others) is this one by Jeremy Early.
BBC Living World on Radio 4 broadcast a programme on the heathland potter wasp in November 2010, still available on iPlayer here. Not the wasp that made the cells I found but interesting none-the-less.
iSpot now has 3 pictures (including mine) of mud cells made by this dapper little spider-hunting wasp: 128290, 169596 and 199972, all of which have been identified by David Notton.
I also found this rather more detailed tome: O'Neil K (2001) Solitary wasps: behavior and natural history. Cornell University Press. Preview only available on Google books here.

3 comments:

  1. Hi Chris. They are amazing!
    I've just edited the post as having rotten problems with formatting in Blogger, so I'm glad I didn't lose your comment in the process :-)
    Mel

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  2. Thanks for this. Saw one of these on my doorstep in Sandy last week 29th September. Didn't know what it was.

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