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Southern oak bush cricket: The hitch-hiking insect

Updated Tuesday 9th October 2012

The southern oak bush cricket is spreading across the UK—possibly by vehicle! The OU's David Robinson explains all to Saving Species's Brett Westwood.

In this extended interview from Saving Species, The Open University's David Robinson introduces Meconema meridionale, the southern oak bush cricket, a species first spotted in the UK as recently as 2001.

Generally living in gardens, they are hard for scientists to study. Despite not having wings, these crickets are being spotted further and further afield. Are they really making their way across the country by attaching themselves to vehicles? 

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Southern Oak Bush Cricket Creative commons image Icon Work found at http://en.wikipedia.org/ / CC BY-SA 3.0 under Creative-Commons license A southern oak bush cricket Copyright open university

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Brett:  David, I know you’ve got a particular fascination for crickets, where did that all begin?

Dr David Robinson:  Years ago when I was a student and I did a student project on bush crickets, and I've been studying them ever since, and principally their sound but more recently their ecology as well.

Brett:  And the knowledge base is growing all the time isn’t it for these creatures, because they haven’t had a lot of attention until relatively recently, and now it seems that people are focusing quite a lot on crickets, and in particular their movements through the country, especially through the UK.

Dr David Robinson:  Yes, they’re becoming better known.  They are quite special insects I think.  When you find one it is quite an experience.  And I think now that it’s easier to take photographs, there’s more and more people taking photographs, there are more photographs available, and they’re becoming more popular.  But they are moving, and that’s what really fascinates me.

Brett:  Which are the species that are showing the most obvious movements?

Dr David Robinson:  Well there are two possibly that are the most interesting.  One is the recently introduced southern oak bush cricket, which has somehow got here and is moving, and then there is one that’s been here for a long while, Roesel’s bush cricket, which was at one time restricted just to a couple of sites in Kent, I think, and then has moved across the country.  And both are moving in the same direction: north and west.

Brett:  It’s interesting this.  Let’s concentrate then on that first one, the southern oak bush cricket.  We were fascinated to see it for Saving Species in the middle of a park in London.  When did it arrive here?

Dr David Robinson:  Well of course we don’t know exactly when it arrived, but it was found in 2001 by Roger Hawkins, and he found one only a short while after he’d seen one in France and found out what it was.  And then amazingly he discovered one in the UK, and shortly afterwards another one, and then a small colony, all in the London area.  But now the records are moving northwards, certainly Nottinghamshire, Cambridge very recently, and down in the South West, Bristol.

Brett:  Just describe these crickets to me.  I've not been lucky enough to see one, but I have seen our native oak bush cricket.  A friend of mine always calls that the bathroom bush cricket because it tends to fly round his bathroom windows in late autumn, but these are slightly different.

Dr David Robinson:  They are, and the chief difference is that the one that you find regularly has got, as an adult has wings, and the southern oak bush cricket doesn’t have any wings at all.

Brett:  So it looks, I mean from the photographs I've seen it looks a bit like a spider, a rather large leggy spider.

Dr David Robinson:  Yes.  So when you look at it it’s, for a bush cricket it’s quite small.  It’s about 15-16mm long, so that’s about the thickness of your thumb.  So it’s quite small, it’s green.  It does look a bit like a spider, but what makes it stand out as a bush cricket is its very long antennae and the back legs that are ideal for kicking.

Brett:  So this is a cricket which is flightless, where are the most obvious places to find it?  Chris Perring found it in a park in quite a busy area, so not out in the wide open countryside?

Dr David Robinson:  Not necessarily, no.  You generally can find them by beating trees, holding a tray underneath and banging something against the branches and hoping that it will fall off.  Because that’s where they are during the day, they tend to cling onto the underside of leaves on trees, or possibly on the top surface, and then they’re much more active at night.  So if you go out with a torch and look on the tree trunks you might well find them then.  And of course you might also find the one with wings on, the common one.

Brett:  That’s the native oak bush cricket, yeah.

Dr David Robinson:  Native yeah.

Brett:  So gardens are a really good place to look then, and I suppose from an entomologist’s point of view it’s very difficult to get into people’s gardens really, so they’re an un-surveyed territory.

Dr David Robinson:  Yes, they are, and when you get late on in the year our native bush cricket often comes into the house.  I see them every year in my house.  I don’t know whether the southern bush cricket is going to turn out to be much the same, but I do know that someone has spotted one on their patio door. 

Brett:  Well it would be nice to see one.  Now because they’ve got no wings, and you say they’re spreading, how on earth are they getting around?

Dr David Robinson:  Well it’s a little bit of a mystery, but the speed with which they’re doing it, given that they’re flightless, means they must be having, I suspect some human assistance, and there are two ways in which we could be moving them around.  One is that eggs or young on plants are being moved as a result of plant imports or plant movements around the country, but there’s also been a small number of reports of them travelling on vehicles or in vehicles, and that seems the most likely possibility that they simply travel that way.

Brett:  So they’re hitching a ride really.  They’re hitchhiking crickets, clinging on for dear life as we move them around the country.

Dr David Robinson:  They are, yes.

Brett:  Well it’s an interesting thought, and of course we might not know that they’re around on the bumpers or whatever, you’ve got to give them credit for that.  I suppose they could have come under the Channel Tunnel really in the same way couldn’t they?

Dr David Robinson:  Yes, that’s quite a possibility.  It’s going to be very difficult for us ever to know whether it was the Channel Tunnel or a pot plant that brought them in in the first place.

Brett:  Now again I know oak bush crickets, and I've seen photographs of the southern oak bush cricket, they both look very very frail creatures.  They’re rather, almost translucent green.  They look like typical vegetarians, typical grass munchers, but that’s not entirely true is it?

Dr David Robinson:  No, it’s not, they’re actually carnivorous, and we tend to think of bush crickets as being insects that feed on plants, but they don’t all and there are others that are omnivorous or can be carnivorous under certain conditions.

Brett:  And what about the sounds that they make?  We’re very familiar that crickets make sounds, are these typical?

Dr David Robinson:  No, again absolutely fascinating.  As far as we know, well there have been one or two reports that they might produce sound, they communicate using vibration.  They drum the hind leg on the surface that they’re standing on, and those vibrations are communicated through the plant.

Brett:  That’s fascinating; it doesn’t sound like we can hear them though.

Dr David Robinson:  I don’t think we can hear them.  You probably would have to have a special microphone or something that picked up the vibrations in the plants.  There are other bush crickets known to drum.  There’s a very large one that occasionally gets imported into this country called Jamaicana and that drums and makes quite a noise.  I've heard it on the side of a metal cage and you can really hear the drumming, but it oddly enough also produces an audible sound. 

Brett:  Now people will wonder if this new cricket, the southern oak bush cricket, will have an effect on our native species.  Do you think that’s likely?

Dr David Robinson:  I don’t really think so, but of course we have no idea whether it will have an effect.  But I should think that they will simply co-exist peacefully.

Brett:  Well we hope so.  Now one thing this creature does raise is the fact that it lives in areas which many people can’t get into unless you’re the property owner, so therefore we need people to send in records.  So what’s the role of iSpot in charting the progress of the southern oak bush cricket?

Dr David Robinson:  Well I think iSpot is the ideal way to record these occurrences, and particularly because people, if they see them around their house they can quickly collect them, photograph them and send those photographs to iSpot.  There are eight records at the moment, and three in September – Bristol, Cambridge and I think the third one was London – as these records come in and they’re plotted, they’re passed to the Biological Records Centre who put them on their map, and so the map will show the spread as well.  And there’ll be a way of visualising the data that’s gone into iSpot.

Brett:  So that’s very useful.  People can actually make a big difference to our knowledge of the spread of this creature.  One thing I did want to raise though, David, of course is that the youngsters look very similar to young oak bush crickets which also don’t have wings; they haven’t developed wings by then.  So I suppose October is a good time because then if you see any without wings it’s much more likely to be the southern oak bush cricket.

Dr David Robinson:  Yes, really they’re distinguishable when they’re adult.  In fact the young stages of quite a few bush crickets are difficult to pin down and identify, so it’s the adults that are I think going to be the easiest to record.

Brett:  And the time of year is also important isn’t it?  So people say that they’ve found them quite late on in the autumn.

Dr David Robinson:  Yes.

Brett:  That means it’s more likely to be adult.

Dr David Robinson:  The eggs tend to hatch in June.  It’s difficult to know what happened this year because we had such terrible weather, so they may have hatched a bit later on.  But certainly autumn and then late autumn around the houses I suspect.

Brett:  So send those records in, and they will be processed and sent to the relevant biological recording centres so that we get a bigger view of how the southern oak bush cricket is colonising Britain.

Dr David Robinson:  Yes, and one thing that some researchers I hope will study is what is actually causing this movement, because forty years ago when they were in Southern Europe something must have changed such that they made this long journey, because it’s quite a distance to have travelled from Southern Europe to middle England.

Brett:  Peckham yes, thank you very much, David, that’s really helpful, and we hope that people will send in lots of records.

Dr David Robinson:  Thank you Brett.

 

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