Tuesday, 10 January 2017

Lithobius sp.

I was recently contacted by a chap called Tony Barber. He runs the Centipede Recording Scheme in Britain, has done for a long time. He also wrote various books and keys that centipede enthusiasts use. (That sounds a bit geeky, like bird-spotter instead of birder. Should I write chilopodist maybe, or myriapodist?) So when he asked me to have a good hard look at the centipedes up here on Skye I was partly thrilled and partly daunted. Apart from good numbers of Strigamia maritima under rocks at the beach, I'd only managed to find three individual centipedes (and two of those got away!) despite checking beneath countless stones, rocks and logs. Millipedes by the bucketload, but centipedes? I hadn't even found Lithobius variegatus yet (and that's the one that's everywhere!) The one centipede that I did manage to successfully pot up and check turned out to be Geophilus insculptus, which is the first record for Skye. You can read that particular post here.

However, I wasn't having any further luck finding more centipedes. Until yesterday that is, when I found a medium-sized Lithobius under a log, plus a small one in standing dead wood which I haven't looked at yet. Problem is that I'm not sure which species I've got. I ran it through the keys a good few times, it heads off to Lithobius melanops every time. But comparing my specimen with the images on the BMIG website it seems that the shape of the forcipular coxosternite is all wrong. Which leaves me a bit stumped. I'm not about to 'make it fit the key' and push a record through (although in fairness it does fit the key, it just doesn't match the pic!) and I rather doubt BMIG have put up a wrong image. Is there a degree of variation in melanops? Is it an age/sex thing? Mine is female if that means much? I just don't know. I've asked a friend for help, he knows about these things. 

Check the shape of the deep cleft between the 4 teeth in the middle, and of the shoulders to either side of the teeth.
BMIG's image from their website (same link as above). Check the teeth, cleft and shoulders - quite different!
Mine's right at the top end of the size recorded for Lithobius melanops (17mm), so it's not a youngster that has yet to 'fill out'. I dunno, looking at it now my one seems pretty close to the BMIG specimen. Maybe there's nothing in it and I'm just being paranoid. Skye feels like uncharted territory for invertebrate recordings, it really is a bit like a Lost World, and I feel that folks are almost expecting me to unearth a few good myriapod records. Basically I guess I really don't want to balls it up. 

Here are a couple more pics of my centipede. All of poor quality, naturally! 

Detail of ocelli - I think there are ten on each side.
Head viewed from above
Coxal pores are round not oval or slit shaped
Female gonopod spurs 2+2
Rather annoyingly this specimen has no ends to its back legs. I must have damaged it somehow in the process of capturing it. The key suggests it should have a double claw. Luckily I have the tops of the legs and can see there are no extra accessory spines between VpP and DpP which rules out Northern specimens of L.borealis a species very similar to melanops, although ruled out in this instance by the greater size of my centipede. L.borealis is stated to top out at about 12.5mm so I need to check any smallish examples for that. It has been recorded from the top end of Skye before, so I look forward to finding it too at some point.

EDIT: I'm now satisfied that this is indeed Lithobius melanops. Since capturing this individual I have found and keyed a second individual which is also Lithobius melanops (11th Jan from under a stone in woodland). 

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