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With a life's experience of teaching field studies in the Forest of Dean, Brian Cave explores the ecology of rural France. More Info

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An English Naturalist in France

Paralysed crickets

October 20, 2014

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In this  drainage groove of a bedroom window, crafted to take away rain water which may have run down the window pane, are fifty seven bodies of  crickets.  None are dead.  They are all paralysed by the sting of a wasp.  There is a great deal of dead grass with the mass of insects.

I have seen this occurrence  in most of the last ten years. Although I find it interesting, it has not occurred to me that this may have more interest than I thought.  In itself it is an interesting phenomenon of nature even though well documented. 

There are various species of  narrow waisted wasps which gather  prey and paralyse them, placing an egg on the bodies. On hatching the larvae proceed to eat the paralysed prey and emerge the next season to continue the cycle.  I have described this before in the case of the Sceliphron wasp which makes little pots of mud which one can find, as I did, on curtains.

I analysed the different species of crickets amongst the 57.  Forty one were Meconema meridionale (29 female and the rest male) ; twelve were Meconema  thalassinum – all male. And then there were single specimens of Oecanthus pellucens, Phanoptera nana and two other  uncertain species.  the Meconema are called Oak bush crickets in English.

There is much more to all this.  But first let me sort out a bit of English/French translation.  What in English are called Crickets are in French ‘Sauterelles’ (= the things which jump).  What the French call Criquets, the English call ‘Grasshoppers’ which is all very confusing. [Criclets/Sauterelles have very long antennae - Grasshoppers/Criquets have short antennae]

There were no grasshoppers in this cache of the wasp.  The Meconema species of  ‘crickets’ all live in the foliage of trees, fairly high up.  They are all nocturnal, hunting at night for aphids, small caterpillars and other tiny creatures – they are carnivores.  The Meconema meridionale or ‘Southern Oak Bush Cricket has no wings so it cannot fly.

More – The M. meridionale used to be  rather rare.  Until 2001 it had not been found in Britain but is now widespread in the southern counties.  Forty years ago it was confined to Southern Europe.   As it cannot fly this spread seems astonishing!

Whatever the wasp is, it makes a habit of collecting the Meconema ‘Oak Bush’ crickets. It has to carry each one – thrust it into the hole where the water should drain and then stuff in a load of grass, having laid an egg on the paralysed prey.   And it did this 57 times. I guess it does this in the daytime when this particular species of  cricket is trying to keep quiet and hidden under the leaves.

As for the wasp – what could it be? I searched my books and found no satisfactory name which matched the phenomenon.   Then I posted a picture of a then unknown ‘cricket’ from the collection – the Phanoptera nana  and a response suggested that the wasp was a species called Isodontia mexicana.  I had no idea of this name. Google came up with the ‘Mexican grass carrying wasp’ .

That appears to be the fellow.  There was a tremendous amount of dead grass with this cache of paralysed crickets.  It is a North American species which arrived in France in the 1960′s and is now found throughout the country.

This is also an account of the extraordinary spread of species which we are experiencing in this current age.  The prey (from Italy) and the predator (from N.America)  meet in Europe and a new ecological relationship comes into being.

 

by Brian Cave. Find out more about Brian Cave here.