On the 22nd of August, a brave team of RoAMers were led out on Tadham Moor by Bill to find the Large Marsh Grasshopper (Stethophyma grossum).
There was doubt at the start of the day whether we would find any – not proof of absence, but it was noted that very few had been seen on anyones wanderings on the levels. As with any species, the numbers LMG will have peaks and troughs year to year, and perhaps this year we won’t see the numbers we have been privilaged to see since its rediscovery in Somerset. Second to this, the weather was not quite on our side, being a bit breezy and overcast when we set out.
The LMG is the UK’s largest native grasshopper, and rumoured to be the UK’s heaviest native invertebrate (I’m sure Fred told me that one). Beyond it’s size, it’s key ident feature is it’s go-faster stripe along the rear of the thigh. It is also one of the rarest Uk Orthoptera having just a single stronghold in south Dorset having disappeared from others areas of the country.
Our first field was a location that in 2019 yielded the first rediscovery in Somerset, by Fred et al. The weather was a bit on the cool and breezy side for find grasshoppers or crickets and our initial results showed that. The ten of us spread out to conduct a sweep of the whole field, like a rural and possibly inept CSI. Initially the most notable observation was the lack of any sightings, let alone the LMG. A few members, including myself, were new to the Large Marsh, so every invertebrate movement was exciting – a potential sighting of the elusive beast. As most exciting bird spots end up in being a pigeon, every motion seemed to be a Crane Fly (Not to put down Crane Flies, they are wonderous creatures equally deserving of our full attention). On completion of our lap, we had just one likely spotting of LMG, by Alan, that scurried quickly into the dense layed grass. We also had some good sightings of Roesel’s Bush Cricket (Metrioptera roeselii), a species confined to the South East coast of England until the 1900’s. It has recently started to spread North and West, is common across much of SE England and spreading well into Cornwall, Wales and northern England. It’s recognised for its distinctive pale line sweeping around its shoulder.
Undeterred, we moved onto a second field, known as the ‘Biblical’ field for it’s vast numbers of LMG on the previous survey in 2019. Having avoided the Longhorn cattle, we were forced to take shelter to wait out some strong rainfall – one that was noted to have not been in any of the forecasts. With Bill not being waterproof, and our target species being a definite fair-weather grasshopper we were close to retiring for the day. Luckily it was just a shower.
It’s thought the Biblical field was once a ‘Hospital field’ – one high in botanical diversity used to put sick animals in to graze where they could get the additional nutrients needed to recover. It was certainly noticably more diverse that the previous field and had great shelter from mature trees on every boundary. The hype given to the field did not disappoint, and several LMGs were found within the first few minutes. A full sweep resulted in 13, all males. Dispite the slightly dull weather there was one male trying to start calling for a mate, but he was perhaps put off by the sudden crowd around him. I don’t blame him for getting stage fright. The LMG has a unique call that differs from other grasshoppers. It creates its sound on the upstroke of its hind leg rather tan the downstroke, so it can only produce a very short call, almost like someone making a kissing moise. I had the fortune to revisit the field a week later on a calm sunny day to hear an uncountable number of males calling for mates in a number of leks. I didn’t venture into the field as I didn’t want to trample or disturb, but it was an incredible soundscape I’d never heard before.
The last observation that should be noted is the presence of the Wasp Spider (Argiope bruennichi). A very striking spider with an incredible web (look up Wasp Spider stabilimenta), but one that preys on grasshoppers. The increase of these has been noticed over the summer across the levels and it’s sure to have an impact on the Large Marsh Grasshopper, but one that will just have to be observed. Nature init.
Our total was 14 LMGs, and 1 Wasp Spider. Big thanks to Bill for leading the day, and to all who turned out to scrabble about in the grass.
All images here are the copyright of Simon Keyte.