Synanthropic Beginnings

Hello everybody, here's wishing you all a Happy New Year and hoping it's one where we can resume our lives with far less restrictions than last year!

So I began the year by cheating. Start as you mean to go on, I say. Shortly before midnight I went on a search for species No.1 and, after a mad panic that I'd fail, found the fella I was after. Then it was just a matter of waiting for the date to click into 2021...

Pholcus phalangioides behind my bathroom sink

This spider is a bit of a gimme in my annex. If nothing else, this image reminds me that I need to paint the plywood I used to patch an area of crumbling wall. And maybe wipe the dust from the wastepipe too! Pholcus typically occur indoors, but I've seen them outdoors a few times too, though always in relatively sheltered spots. These are tactical hunters, preying upon other spiders which they ensnare and immobilise in copious amounts of silk before delivering the killing bite. 

I took myself on a quick tour of the outside walls, beginning by saying hello to the second of the three gimme spider species I knew I could easily secure. 

Tegenaria domestica on its sheet web

This chap/chapess lives by the doorway to the boiler room. Tegenaria domestica is the only species in the genus known to occur on Skye, though I'd love to prove that wrong some time this season. This is a small individual and I expect it will be easy to find throughout the year, as they can live for some time. I occasionally find one stuck in a blunder trap, so they do come properly indoors too. 

A quick scan of the outside walls with my head torch revealed the third spider of the year, one which I half-expected to find but always nice to actually bump into.

Female Amaurobius similis on her nocturnal wanderings

There are three species of Amaurobius in Britain, all fairly similar looking. A.ferox is darker than the other two and doesn't have annulated legs though it does sometimes occur around buildings. A.fenestralis and A.similis look very similar to each other, but have different body shapes and fenestralis tends to occur in the wilds, rather than on buildings. I have seen it in nearby Uig Wood, but not around the hotel walls. 

There's an outbuilding in the middle of the hotel grounds that stays lit all night. As such it often attracts small flying insects, which in turn attract spiders. It's also where my third and final gimme spider species resides. I went and wished them a happy new year...

Zygiella x-notata guarding her egg sac at the wall/ceiling interface

This time last year there were a dozen or so Amaurobius similis also living in the shed, but I haven't seen a single one for some months now. Happily, that changed tonight. Maybe they're staging a comeback.

Welcome back!

So that concludes the spiders I found on my little wander. What about the flies, not including the dead ones in the image above. Just two individuals, both on the walls of the hotel, sheltering from the cold rain.

A Sylvicola, one of the Window Gnats

And a Tipula, one of the craneflies

I popped both of them into pots and brought them indoors for a closer look. There aren't too many craneflies that fly in January and this one is particularly easy to identify. Check out the broad blackish bar that runs horizontally from behind the head and extending to above the middle coxa. The only largish tipulid with that streak is Tipula rufina, one I see fairly infrequently on the hotel walls/windows.

Tipula rufina - a nice easy one to identify

The Sylvicola I had to examine more closely, which meant knocking it out with ethyl acetate and examining it beneath the microscope. There are only four species in the genus, but I've had three of them here in Uig, and two of those differ very subtly, hence the need for a close examination. 

First up, I needed to check whether or not the bases of two veins were situated next to each other or were separated by the length of a cross-vein. In the image below I've added my trademark red dots to highlight the veins in question.

The veins are clearly separated from each other at their bases

This rules out Sylvicola punctatus, which is one I've seen here before. Three species to go...

Next we need to check the hind femur to see if it's entirely yellow or if there's a blackish ring/marking halfway along its length.

The hind femur is clearly darkened in the middle section

That rules out Sylvicola zetterstedti which has an entirely yellow hind femur, again that's a species I've recorded here before. 

The remaining two species are Sylvicola cinctus, which is by far and away the commonest one I find here, and Sylvicola fenestralis which I have never seen, despite it supposedly being common throughout Britain. In males it's a case of checking the claspers for differences. Mine is a female, so the differences are somewhat more subtle. Both have wing markings though these are often paler in cinctus. Both have hind femur markings though again these are often paler in cinctus. S.fenestralis always has three black stripes across the top of the thorax and has a wing length of 5 - 7.5mm. S.cinctus may have black stripes across the top of the thorax, but more usually they are either brownish or absent and the wings are only 4.5 - 6mm in length. 

Black thoracic stripes and a 7mm wing length - so it's fenestralis, right?

Well I did not expect that! I double-checked, definitely 7mm wing length which puts it outside the size range of cinctus. I didn't like this, second fly of the year and it's a lifer? I went online for more info, I needed to see what the female's terminalia looked like for fenestralis and cinctus.  

This is a (rather poor) pic of the underside of the abdominal tip of my gnat

Ignore the black thing extruding from the tip

So you have what looks like a pair of rounded teddy bear ears sticking out - just let me know if I'm getting too technical for you here. Below and between the bases of these teddy bear ears is a pale orange, slightly rounded plate with a shallow incision in the middle of the upper edge. I hope you can make that out, because it's important. Here's an image of the same features taken by someone with a proper camera set up

Note the notch in the middle of the upper edge

Guess what - this is Sylvicola cinctus and not fenestralis! Possibly the biggest cinctus known to mankind, but the genitalia don't lie, as a famous female singer once said. Something to be aware of for everybody who keys out invertebrates, the keys are a guide, not gospel. Some are undoubtedly better guides than others, but none are infallible. 

And here it is ready to go into the Nematocera Storebox, safe and sound just in case I need to revisit it at some stage in the future. As Julian Small, expert on all things to do with gnats, once told me, "I wouldn't be surprised if there are species still awaiting discovery in the more wild and woolly parts of the country". Maybe this is one such beast? Skye does fit the wild and woolly category, especially on a New Year's Eve! 

The Sylvicola key I used is this one.