Dear Readers, after our spider walk a couple of weeks ago, an intrepid group of spider admirers (myself, Cassandra Li and spider expert Edward Milner) decided to pilot a walk in Coldfall Wood after dark. We knew that glow worms ( a kind of beetle ) had been found in the woods in 2009 and 2010, but there are also many insects and arachnids that are active after dark. We had no idea what we would find, but setting off into the darkness of the trees with our head torches was a fascinating experience, and even I, who have been known to fall over for no apparent reason, managed to stay upright for once.
It was astonishing how many different spiders we saw, but then many of them are nocturnal, lurking in the crevices of oak trees and the interstices of man-made structures such as handrails and fences.
Take the spider in the photo above, for example. Amaurobius similis, like many lace-web spiders, is largely active at night, and this was a very fine specimen. If you look to the left of the photo you can see the spider’s web, which it often builds after dark – when fresh, the strands have a faint bluish tinge, hence the alternative name of the group as the blue-web spiders. This type of silk is known as cribellate silk, a word that means ‘sieve-like’. It’s produced by an organ known as the cribellum, which is filled with tiny holes through which the silk is pushed and then combed out, producing a woolly texture. The fibres absorb wax from the cuticle of any insect that contacts it, and furthermore it doesn’t dry out, unlike the sticky threads of more conventional webs. Interestingly, some spiders can switch between cribellate silk and the ‘normal’ spider silk that we see in our gardens.
Along the handrails of the bridges, nearly every joint was occupied by a Silver Stretch Spider (Tetragnatha montana) – they reflected silver in the light of our torches, but seemed completely unconcerned by our presence.
When we came to the wetland area, we passed a dead tree. On our previous walk, Edward had mentioned that it was a perfect habitat for the Flattened or Walnut Orbweb Spider(Nuctenea umbratica) – the spider hides away beneath the bark during the day, and then spins a huge orb web at night, catching moths and mosquitoes. It really is a very impressive spider, and one I’d never knowingly seen before. I love the way that the shadow in the photo makes it look even more splendid. That woodlouse had better watch out.
Cassandra was great at getting these night photos with a combination of a torch and an iPhone. I was very impressed.We even had one new spider species – Agalenatea redii. This is a little orbweb spider, more commonly found (at least according to my Britain’s Spiders field guide, highly recommended) in rough grassland. She (for indeed it was a female) was a very attractive spider when viewed with the hand lens, and it goes to show that although animals sometimes behave as predicted, very often they don’t.
By my reckoning, this brings the total number of spider species found in Coldfall Wood to 142 species, not bad when you consider that there are only 670 species in the UK, and most of these are miniscule little money spiders, extremely difficult to identify to species level.
We didn’t just see spiders, either. We found a number of slugs, including this one (which I think is a Yellow Cellar Slug), who seemed to be strangely attracted to this slime mold, which we think is Stemonitis fusca. What interesting structures slime molds form! I can feel a slime mold blogpost coming on. But I digress….
And on the subject of ‘dangly flies‘, how about this Tiger Cranefly (Nephrotoma flavescens) – the length of the legs is really something. What a handsome creature it is!
And so we had a great time in the woods, and even managed to get (briefly) lost – it’s interesting how everything looks the same after dark, and how easy it is to get turned around. Sadly, the one creature that we didn’t see (this time) was the elusive glow worm. This is not a worm at all but a beetle – the female emits a glow to attract the male. I’ve only seen them once in the UK, in a hedgerow near Slapton Sands in Devon, but the London Wildlife Trust is asking people to look out for them in London, as there are already a couple of sites, and they could be overlooked. The larvae eat snails, so are very handy for the ecosystem.
There are two species of glow worm in the UK (well, 3, but one species hasn’t been seen since 1884), and as far as I remember, the one in Coldfall was the Lesser Glow Worm, which is extremely rare, but not as brightly lit as the ‘ordinary’ glow worm – the female has two little lights on the back of her abdomen, which makes her very difficult to find. No wonder we had problems! But we haven’t given up hope, and will certainly be keeping our eyes open next summer. Who knows what we’ll find?