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!).

Rockpooling at Helford Passage

One of my modules at university this year is Invertebrate Zoology. So far I’ve been loving it of course! The first of four practical sessions for the module was at the Helford River Passage, a rocky shore estuary where we would be tasked with finding as many invertebrate groups as we could, and then classifying three organisms from domain down to species. This was a great opportunity to find (and be shown) some interesting new species, as there were about 100 of us, all searching for invertebrates!

There was a small group of sea snails that were immediately obvious, the Topshells. Unfortunately, I don’t have any photos of these species, but when I do, I’ll get them online and point out the features for telling them apart! The species that we found on the day were Purple Topshell (Gibbula umbilicalis), Grey Topshell (Gibbula cineraria) and Common Topshell (Osilinus lineatus).

Soon after the Topshells, I found both Common Oyster (Ostrea edulis) and the invasive Pacific Oyster (Crassostrea gigas). The difference between these species is relatively easy to see, as the Pacific Oyster has much larger ridges (hence also deeper troughs) in the shell than our native Common Oyster. The Pacific Oyster has escaped from hundreds of Oyster farms around British coasts, and has established itself in many locations, particularly in Cornwall. In other parts of its range, the Pacific Oyster has become so abundant, that it completely excludes other species from suitable habitats. It is a worry that our native, slower growing Oyster will begin to decline, or even disappear in areas where the Pacific Oyster is present.

I then went down to the lower shore with a very small (but free) net, to see if I could catch any fish or prawns amongst the rocks. I decided that dragging the net along the bottom, and through clumps of Serrated Wrack would probably be the most productive, as these are the places where my target species would be hiding from predators. I was proven correct, after several hauls of Common Prawn (Palaemon serratus), but unfortunately no fish. I’d managed to gain a reputation amongst my fellow rockpoolers by having a knack for catching prawns! This reputation was cemented after I managed to scoop up this gigantic prawn, earning me the title of ‘The Prawn Whisperer’. The upcurved rostrum, with serrations absent in the apical third are diagnostic of the Common Prawn, Palaemon serratus.


I was just about getting bored with the endless supply of Prawns, and was about to head further up the shore when I spotted a very unusual looking anemone just below the surface. I bent down to pick up the stone it was attached to so I could take it up the shore and show my groupmates, but as I grabbed it, the stone started to run away! The stone was in fact a Shore Crab (Carcinus maenus), and the anemone was the Parasitic Anemone: Calliactis parasitica. The Parasitic anemone is usually found on the shells of Hermit Crab species, so finding it on a Shore Crab surprised even our lecturer! The relationship between the crab and the anemone is mutually beneficial, with the anemones stinging arms offering the crab protection, whilst the movement of the crab causes more food to pass near the anemone. This is true for a small Hermit Crab, but I’m not certain that this 8cm Shore Crab needed the anemones protection at all!


Most people managed to find Hermit Crabs, but the only other Parasitic Anemone found that day was on another Shore Crab! It makes me wonder if this occurs more frequently than we currently know about, with all texts that I’ve read seeming to say the Hermit Crabs are the only host. It was pointed out to me that it makes the Shore Crab look like it’s wearing a beanie.


Another highlight from that day included my first Bryozoan, the Star Ascidian (Botryllus schlosseri) which is well worth a google search, as it forms beautiful colonies, and I forgot to take a photo of it! The colony that we found was bright orange-red. Also, I saw my very first Brittle-stars. The larger individual was about 8cm across, the smaller one about 2cm.



Finally, a little later on in the day I wondered through the woods just outside of the Penryn campus with my flatmates, when one of them found this stunning Pale Tussock moth caterpillar crawling across the path! After metamorphosis it turns into a very lovely, very furry (but very grey) moth.


Species of the week- 4

The species this week is the non-native micro moth Tachystola acroxantha. Its homeland is Australia, but it is now introduced to the UK, the rest of Europe, and New Zealand, probably as larvae, eggs or cocoons in plant pots. Its first British record was from Devon in 1908, and the species remained South-Western until the 1990’s, when it began to rapidly expand its range. It is now found throughout Southern coastal counties, in Southern Wales, East Anglia and North to Lancashire. This range expansion is almost certainly associated with climate change, bringing our own climate slightly closer to that in Australia. T. acroxantha is commonest in the South-west, London and Bristol areas. See the distribution map here: 


The impact of the invasive T. acroxantha on native species is relatively unknown, but I think it is unlikely to be very significant. The larvae feed on dry leaf litter, in a loose silken tube, so are unlikely to compete with very many other species. Also, despite expanding its range very quickly, T. acroxantha never seems to be very abundant where it occurs. So far, from two nights of moth trapping at the Penryn campus (in Cornwall, where T.acroxantha is frequent), I’ve seen one individual. I’ve also found a single, fairly fresh adult whilst beating Oak, pictured below:


That brings me nicely on to identification. When fresh, this species is unmistakable. The moth is 7-10 mm in length, and the unusual overall shape and bright yellow patches along the termen (which is incurved, adding to the odd shape) are diagnostic. Problems with identification only occur in very faded specimens, where the ground colour may fade from red-brown to grey, and the yellow may be worn off. In these instances, confusion with other members of the family, such as the ubiquitous Brown House Moth (Hofmannophila pseudospretella) is possible. Unless the wings are very damaged, the shape of the moth is usually still distinctive.

Tachystola acroxantha is best found by moth trapping in garden or parkland areas where it is most abundant (the South-west, London etc.). It probably has multiple broods through the year, as it can be caught from April right through to December. I have no experience in finding the larvae, but sifting through leaf litter in suitable situations would probably be a good place to start.

In conclusion then, this attractive little moth seems to fit in with our native Lepidopteran fauna quite harmoniously, so I won’t be complaining when it turns up back at home in Huntingdonshire! My prediction is August 2018.


Species of the week-3

This weeks species I found for the first time on Wednesday (14/09) at Kennall Vale Wildlife Trust reserve near Ponsanooth in Cornwall. The pseudoscorpion Roncocreagris cambridgei, also known as Cambridge’s Two-eyed Chelifer. Quite a mouthful whichever name you use!

I’m almost ashamed to admit that this wasn’t just the first time that I’d seen this species, but the first time that I’d seen any pseudoscorpion at all. I’ll have to make up for it by finding as many as I can from now on. 

Here is my phone-microscoped specimen of R.cambridgei:


Surprisingly (if you aren’t familiar with pseudoscorpions) this species only reaches around 2.5mm in length, and the largest British pseudoscorpion is only around 5mm. The small size, and habit of living in under stones and in the soil makes R.cambridgei rather under recorded, like all British pseudoscorpions. 

R.cambridgei, like other pseudoscorpions, is highly predatory. It catches its prey simply by running after it, and grabbing it with its enlarged, pincer-like palps. It then chews its prey, and uses digestive juices to liquidise the victim, which can then be ingested. They prey on mites, larvae of various small insects, and very small flies. I found that the pseudoscorpions were quite aggressive when I tried to pick them up, lifting their palps into the air, and actually gripping to my fingertip using the ‘pincer’ when I tried to let go!

This species has a predominantly South-western distribution in the UK, but also occurs in Western Scotland, with isolated records elsewhere. This again seems to imply that it is under recorded, and should occur in many more localities. See the distribution map here: 


I found several R.cambridgei under a stone on dry soil in a mixed woodland, which is classic habitat for this species. The rest of the reserve is much wetter, implying that the population of the site may well be restricted to that one small area. When I next visit I’ll check the wetter areas more thoroughly, to see if the species also occurs there, or whether our current understanding (that this species only occurs in dryer areas) is correct. Other pseudoscorpion species can be found anywhere from under seaweed at the high-tide mark, to high in the treetops in bird nests, and even in dusty corners in houses.

For more information on pseudoscorpions, including how to identify Britain’s 27 species, follow this link to the provisional FSC key: 




Kennall Vale

Kennall Vale Wildlife Trust reserve is my new local patch, in the village of Ponsanooth just a bit further inland than the University campus in Penryn. The reserve is a damp mixed woodland, with a stream flowing through the middle, and the ruins of a gunpowder factory near the paths. The gunpowder factory has been closed for around a century, so is now covered in mosses and ferns.


My latest visit was this Wednesday (14th September), when I spent a few hours slowly wandering around, turning the numerous stones and logs! The first large log that I turned over was on particularly dry soil, but still yielded several Lithobius pilicornis, one of Britain’s largest centipedes. It’s very fast, and can bite, so I unfortunately didn’t manage to catch one for a photo. Much to my surprise, I also found a small group of pseudoscorpions, the first that I’ve ever seen! I took a few specimens back to identify, and found that there were two different species from under the same stone. One was Chthonius ischnocheles (The Common Chthonid), and the other was Roncocreagris cambridgei (Cambridge’s Two-eyed Chelifer). Roncocreagris cambridgei will be covered in detail species of the week, but here’s a quick overview of pseudoscorpions: they’re usually 2-4mm long, and look like this! (Photo is of Roncocreagris cambridgei, phone-microscoped).


Many logs and stones later, I managed to find a particularly special centipede: Stigmatogaster souletina. This species is one of Britain’s thirty or so Geophilomorphs, or ‘Earth Centipedes’, so called as they spend most of their time in the soil. S. souletina is a particularly interesting species, as it’s found only around the Falmouth area, and is Britain’s longest centipede, reaching an impressive 9cm in length! This specimen was around 7cm in length. Unfortunately the photo is slightly blurred in the low light.


Under that very same log was another lovely species, from an even more unpopular group of organisms than centipedes! Arion owenii, which I know as the Irish Garden Slug, but the current vernacular name seems to be Tawny Soil Slug. I feel as if my view that a slug can be ‘lovely’ is a fairly unusual one, but in my opinion, the warm colour and prickly texture (given by raised tubercles on the back) of A. owenii make this a very nice species to find, and very distinctive. It has a distinctly Western distribution, but is not considered to be common even here. That said, it seemed numerous enough in places of Kennall Vale. Here’s the distribution map: 


And here is the wonderful slug itself!


Other highlights during the day included the Chrysomelid beetle Oulema melanopus, another lovely Slug: almost certainly Ambigolimax nyctelius, and hundreds of the non-native Landhopper (Arcitalitrus dorrieni). The photographs are in order of mention. I had the pleasure of finding all these lovely invertebrates whilst surrounded by at least six species of Fern, in a beautiful woodland with Nuthatches and Ravens calling overhead. Kennall Vale is a gem of a reserve, and I can’t wait to visit again soon. What an amazing welcome to life in Cornwall!



Species of the week-2

This weeks species is Reduvius personatus, Britain’s largest species of Assassin Bug (family Reduviidae).  This impressive bug can grow up to about 2cm in length, and is found mostly near human habitation. It is nicknamed the Masked Hunter as the nymphs of this species secrete a sticky substance, which causes dust and debris to stick to their body and act as a camouflage when hunting. Both the nymphs and adults are predatory, and feed on a wide range of invertebrates, including Earwigs, Flies and Silverfish.

Reduvius personatus, like all true bugs (Hemiptera) feeds by essentially stabbing its prey, and then sucking it up. Being such a large and powerful bug, the beak of Reduvius personatus is strong enough to pierce human skin, and so deliver a painful bite. Fortunately it doesn’t bite unless picked up and handled roughly, so it’s usually entomologists that get bitten, and they don’t seem to mind too much!

My only encounter with the species was at my garden moth trap in July 2016, when one adult was attracted to the light (they’re fully winged, so fly well). Unfortunately, I don’t have any tips on how to find the species, other than to spend time at or near houses and get very lucky! I didn’t pick it up, however I did manage to get some nice photos:


You can see the lower part of the beak in the top photo, folded round underneath the body. This is held out in front of the insect when attacking prey. I’ve always thought that its dark colour and thick, sculptured-looking wings make this look like one of the most sinister British insects!

Reduvius personatus is almost certainly under recorded, but seems to be quite widespread in southern England and Wales. Here’s a link to its distribution map: 


Hope you’ve enjoyed the blog. I’d love to know if anyone else has found Reduvius before, and how. Please leave a comment if you have!