Nocturnal beetling and more at Woodwalton Fen

On Saturday the 15th of July, at about 10:30pm, Brian Eversham and myself headed out to Woodwalton Fen NNR to see if the rare Tansy Beetle (Chrysolina graminis) is nocturnal or not. Our side aim was to find as much else of interest as we possibly could!

We crossed the bridge over the Ramsey Forty-foot Drain to enter the fen, armed with head-torches and sweep-nets. The first thing we came to was a large Oak tree, so we decided to stop and stare at the bark to see what interesting invertebrates were climbing Oak trees at night. We spent some half an hour at the Oak tree, finding bush-crickets, moths, caterpillars, harvestmen, and even the occasional ground beetle. At one point, Brian spotted an odd-looking beetle climbing up the bark. On closer inspection, it was a Psylliodes flea beetle, and then I found something lurking in the cracks behind it: a big pseudoscorpion! It turned out to be Britain’s biggest pseudoscorp (at a whopping 4mm), the Red Data Book species Dendrochernes cyrneus, new to Woodwalton, and perhaps Huntingdonshire! Brian has been kind enough to let me use his photos in this blog, so they’re much better quality than normal!

Dendrochernes cyrneus, RDB pseudoscorpion, photo by Brian Eversham

As we moved onwards up the main ride of the reserve, a Grasshopper Warbler sang distantly. I’m not sure why, but I’d never quite realised that they sing in the middle of the night, so it felt very odd to hear one! Our walk was dominated by moths for a few hundred yards, with Fen Wainscot (Arenostola phragmitidis) by far the most abundant, followed perhaps by Anania perlucidalis. The head-torches also attracted Drinker moths (Euthrix potatoria), which being rather ungainly flyers, were repeatedly battering our faces. Luckily they’re rather soft things, so it’s sort of like being hit with a very small cushion. Here’s a selection of moths- photos by Brian again.

Left to right: Udea lutealis, Argyresthia brockeella, Fen Wainscot (Arenostola phragmitidis) and July Highflyer (Hydriomena furcata).

Other moth highlights included Crescent (Helotropha leucostigma), and a huge abundance of Svensson’s Copper Underwing (Amphipyra berbera) on the famous Rothschild’s Bungalow in the centre of the reserve.

The walls of Rothschild’s Bungalow also gave us roosting Red Admiral (sadly no Purple Emperors), the nationally scarce ant Lasius brunneus, and lots of the spider- Scotophaeus blackwalli (Photo from Brian).

Scotophaeus blackwalli, a rather impressive looking spider, which I’d only previously seen in my house!

We then headed towards Tansy Beetle area, but couldn’t resist stopping at one of Woodwalton Fens many bridges, which provide areas of bare ground great for finding Carabids (ground beetles) and Lygaeids (ground bugs). Sure enough, I managed one new species for me from each group! The Carabid Platynus assimilis, and the Lygaeid Scolopostethus puberulus. The latter is identified by having the basal two antennal segments uniformly pale, the apical two uniformly dark, and having a rostrum long enough to reach the hind coxae. All features are shown in my phone-microscoped photos below:

Above: The Lygaeid bug Scolopostethus puberulus.

After these many brilliant distractions along the way, we eventually reached the part of the reserve where Tansy Beetles are known to be found. We checked the stands of Water Mint and Gypsywort (known foodplants) very carefully, and found feeding damage, but no beetles! Luckily we found a few other nice beetle species along the way- the bizarre 2mm Pselaphid Rybaxis laminata, and contrastingly, the 2cm Carabid Carabus granulatus! Both new to me. Below is Brians photo of this beasty beetle!

Carabus granulatus, a beautifully sculptured Carabid.

We continued further into the fen, sweeping the Common Reed and Tufted Vetch, which yielded a new Apionid weevil for me- Oxystoma cerdo. It’s a particularly odd looking weevil, with a ‘roman nosed’ look given by the narrowing and bumped rostrum. Phone-microscoped pic of mine below:

Oxystoma cerdo, an Apionid weevil associated with Vetches.

We also looked closely at flowerheads that we passed, as these were packed full of moths and beetles. One of our best finds was from the head of Common Ragwort- the chunky Curculionid weevil Brachypera zoilus. Photo by Brian.

Brachypera zoilus, a Curculionid weevil usually found at the roots of Clovers… but not at night!

Before heading back, we switched off the head-torches to appreciate the sounds around us, and listen for more Grasshopper Warblers. Unfortunately we didn’t hear any Warblers, but just listening to the wind gently blowing the reeds, whilst looking up at the Milkyway (a rare sight in Cambridgeshire!) was lovely.

So, my thoughts after my first ever nocturnal fieldwork session… brilliant! Compared to fieldwork in the daytime, it seemed much more productive (unless you prefer bees, wasps and most fly families). Each sweep net seems more full, with more interesting things, and the tree trunks come alive! I can’t wait for the next time.

5 thoughts on “Nocturnal beetling and more at Woodwalton Fen”

  1. Thanks Calum, Very interesting as always; are you becoming a nocturnal creature? Most people are in bed around this time of night! Take care…..Pa

    Sent from my iPad



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