Species of the week- 8

This weeks species is the first plant to have made it species of the week, so as you’d expect, it’s interesting, rare and obscure! The Tunbridge Filmy-fern (Hymenophyllum tunbrigense)!

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This species, for me, was the highlight of a recent field trip to Kennall Vale, especially as I never knew it was at the site! Nearly all of the 1st year bioscience students (almost 200 people) were queueing up, wondering what would be so special about the much-discussed Tunbridge Filmy-fern. Most people seemed oddly underwhelmed, but I could barely contain my excitement! I understand of course that to someone with no interest in ferns, this inconspicuous little species looks like a slightly ruffled patch of moss, but I think it’s truly beautiful. Here I am, with the fern!

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The individual fronds of the Tunbridge Filmy-fern are only a few centimetres in length, and are only a very few cells thick. This gives the fern a semi-transparent appearance and film-like texture, hence the ‘filmy-fern’ part of its name. It also gives the Tunbridge Filmy-fern an appearance quite unlike any other British fern species (except for Wilson’s Filmy-fern). This fern can live for many years, and can undergo periods of drought by allowing itself to dry out almost completely.  

Although the Tunbridge Filmy-fern is globally very widespread, it is rare in the UK, being confined to the extreme South-west of England, and the West of Wales and Scotland. It is also found in a few sites in South-east England (near to Tunbridge Wells), where it is declining due to loss of woodland habitat, and shading by introduced Rhododendrons. It is not only a rare species, but can also be very hard to find, as it may only grow on a few rocks in a particular area of a seemingly ideal habitat. I’ll use that as an excuse for not finding it myself on previous trips to Kennall Vale!

Unlike most of my other species of the weeks, the Tunbridge Filmy-fern is well recorded, so its distribution map probably reflects its true range. It is usually found on mossy rocks in damp, shaded, wooded river valleys and ravines. I hope that one day, all other groups of British wildlife will be as well recorded as the plants! Here is the map:


I must apologise for the blog being a day late. This time, blame the Hudsonian Whimbrel. (Blog on recent rare birds coming up midweek!).








Species of the week- 7

Sorry this blog is one day late! I suffered from Cornish internet problems when I intended to write this last night. The species this week is from an underappreciated family of Insects: Formicidae, otherwise known as Ants. There are around 50 species of Ant that can be found outdoors in Britain, and this species is amongst the least conspicuous of them all. It is (of course) Stenamma debile! Unfortunately, there is no common name for this species. Here it is:


It isn’t the clearest phone-microscoped picture I’ve ever taken, but the ant is only about 3mm long! I admit, that compared to some of my previous ‘species of the weeks’, S.debile isn’t exactly stunning, but I hope I can persuade you that it’s still fascinating!

I chose S.debile this week, as myself and a friend Jaimie found two individuals whilst sifting leaf litter around College Reservoir (which, by the way, has a stunning juvenile Pectoral Sandpiper wading its shores at the moment!). This was the first time that I’d seen S.debile for three and a half years! The reason I see this species so infrequently isn’t that it’s especially rare, just that it’s extremely hard to find. It makes very small colonies (usually only 20-50 workers), which live in the soil under leaf litter, so the chance of stumbling across a colony is remote. If (by chance or dedication) you do manage to pick up a sample of leaf litter containing S.debile, your struggles aren’t over! This species is soil/leaf-coloured, 3mm long, moves very slowly, and tends to roll into a ball when disturbed!

Luckily, identifying S.debile when you find it is quite straightforward. General size and shape is usually a good indication, but the features to look for are: 

1) It has two waists, the first of which is relatively longer and thinner than in other ant genera.

2) It has very tiny eyes compared with most other ant genera.

3) It has only very short spines at the back of the thorax (overhanging waists). These spines are longer and thinner in most other ant genera.

4) The long, thin first waist has bulging nodes on each side near its joint to the thorax. This features separates S.debile from the much rarer S.westwoodii, which has no such nodes.

These features can all be seen fairly well in my photo below.


Workers of this ant species are probably mostly scavengers of small dead  invertebrates, but it is likely that they will take live prey if it is small, and slow enough for them! S.debile is a fairly widespread (but as outlined above, probably hugely under-recorded) species, but seems to be quite thermophilic, not having been recorded any further North than Lancashire yet. It has had very few records from Cornwall so far, so I’m very pleased to have found it! Here’s its distribution map:


I wish anybody who tries to find it the best of luck!


Species of the week- 6

I’m not sure quite where the last six weeks have gone. I guess time flies during the first year at university! This weeks species is a truly amazing spider, the Water Spider, Argyroneta aquatica, also known as the Diving Bell Spider. I found my first just yesterday (08/10/2016).

The Water Spider is the 57th species of spider that I’ve found in the UK, and it’s got to be my favourite so far! Here’s a photo taken by my friend Toby Cotton, who I was helping to sample the diversity of aquatic life in our local reservoirs. Thanks for inviting me along, and taking such a great picture!

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As you may be able to tell, this spider is underwater! Hydrophobic hairs on the abdomen allow a bubble of air to be carried round with the spider, so it can spend a long time hunting without surfacing, or returning to its ‘diving bell’. The diving bell is a much larger store of air, created by the spider amongst rooted underwater vegetation. The spider returns to its diving bell to feed, lay eggs, mate, overwinter, and top up its mobile air supply. The Water Spider is also adapted to its underwater lifestyle by having numerous long hairs on its back two pairs of legs. This allows it to swim powerfully enough to offset the buoyancy of its mobile air supply. The spider pictured above had grasped a small piece of leaf in the bottom of our bucket, and accidentally floated it up to the surface! A short while after the photo, the spider dived back down again, and grabbed a more substantial piece of plant matter.

The Water Spider actively hunts aquatic invertebrates, such as insect larvae and water fleas (Daphnia). I feel as though it must also take larger prey, as it can be 20mm in length, and has chelicerae strong enough to pierce human skin, delivering a fairly painful bite. I’m fairly fortunate that I was unharmed that day, as I was handling both the Water Spider, and loads of Saucer Bugs (large aquatic bugs that can stab you with their mouthparts if annoyed)! See photo below, showing curved front legs for grabbing prey.


A.aquatica is fairly widespread in the UK, but quite localised. It requires areas of water that are sheltered, and have very little if any flow. Here’s its distribution map (it looks like this was a new 10km square record, in Penryn!). It seems to be highly localised in Devon and Cornwall, so I’m very proud to have found it!


I hope this has been an enjoyable blog, and I hope people go out and find some local Water Spiders. They’re great!



Species of the week- 5

As winter approaches, it becomes harder to find a good range of interesting invertebrates/plants/other things to blog about, so to stop this from turning into ‘slug of the week’ I’ll sometimes blog about things that are more likely to be found in the summer. 

So, the species this week is Thanasimus formicarius, A.K.A the Ant Beetle, or the European Red-bellied Clerid. This unusual beetle is given the name ‘Ant Beetle’ as the way it moves, and its colouration mimics an Ant. Here is the beetle:


I said that the Ant Beetle mimics an ant, but I tell I lie. Its colouration is very similar to that of the Velvet Ant (Mutilla europaea), which despite its name, isn’t an ant at all, but a solitary wasp. The Velvet Ant can be found in similar areas to the Ant Beetle, and is noted for its painful sting, so is a fairly useful species to be mimicking! Here’s the Velvet Ant for comparison:

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The Ant Beetle spends two years as a larva, before overwintering at the base of a tree, usually a Pine tree. The Beetle then emerges in Spring and seeks out fallen Pine trees and log piles, where it waits for its prey (Bark Beetles) to arrive. Bark Beetles are fairly well armoured, so Thanasimus formicarius uses its strong jaws to bite the legs off, and immobilise its prey. It can then take its time about breaking open the Bark Beetle, targeting weaker areas between the head and pronotum (thorax), and between the pronotum and elytra (abdomen).

I’ve only seen the Ant Beetle twice in several years digging around in log piles! Once was under the bark of a log in Monks Wood, Huntingdonshire, and once was on a coastal heathland in Suffolk, where the beetle walked right past me as I was having my lunch. It is best found by checking Pine stumps, logs and fallen trees, but as with most things, a good dose of luck will help!

T.formicarius is widespread but fairly uncommon in Southern and Eastern England, and has also been found in Northern Scotland. See distribution map here:


One similar species, T.femoralis has been recorded only from Northern Scotland, but appears to be very rare. It can be distinguished by having reddish femora and tibiae (black in T.formicarius). I think that T.femoralis is also smaller (about 6mm), whereas T.formicarius is larger (about 10mm), but I’m not certain! 

The Ant Beetle is one of my favourite beetles, so I hope to see it again soon! (And hopefully in Cornwall, as it’ll be a new county record!).