Wednesday 18 November 2015

Fly Feet and Lizards' Ears

It’s once more into the ditch dear friends this week as we descend into the valley depths and continue our journey up the river bed. It is still dry as the autumn rains haven’t really got going yet and we’re blessed with another gloriously sunny morning for our explorations. We’ll start down here with a little bird-watching by the cane beds and just sit quietly for bit and see who turns up.

Flesh Fly, Sarcophaga
Our first visitor isn’t a bird but one of the house flies and their allies. There are about four thousand different species but they are quite recognisable from the large red compound eyes and the four dark longitudinal stripes on the thorax. This one, as you can see, is slightly larger than your average house fly and has a chequered abdomen so I rather suspect that it is an Autumn House Fly, also known as the Face Fly from its habit of feeding on eye, nose and mouth secretions of cattle and horses.1 Oh sorry, were you just about to get the sandwiches out? It’s a bit early yet isn’t it? Put them away and have a closer look at those amazing feet. Those soft pads on the end, called pulvilli, are what enable them to walk up windows. Not only do they produce a dry glue (which we’ve only recently succeeded in emulating to make a dry sticky tape) but the pads have tiny hairs on them. Getting smaller; each hair is covered in microscopic projections which generate a molecular attraction with the surface upon which the fly is walking so they bond with the surface on a molecular level. Geckos and spiders also use this van der Waal’s’interaction 2, as it is called, but one of the few things that flummox them all is Teflon, so it really is non-stick. 

Leaf Warbler, Phylloscopus
Meanwhile, back to our birds I’ve seen a Blackbird and a Robin pass through while we’ve been chatting about flies and there’s something flitting about in the canes now.  There he is; a little olive green and off yellow job doing his best to keep out of camera range. It belongs to a family of birds called the Phylloscopidae  or Leaf Warblers and, with dozens of species in only two genera, they provide ornithologists with hours of acrimonious fun debating the differences between them. Me? I’m just happy to call them Leaf Warblers and leave it at that. Anyhow, that’s enough sitting around on our backsides, let’s push on up the valley and see where it leads us.

Bracket Fungus, Trametes
This is interesting. Do you remember a fortnight ago when we found a bracket fungus with gills (see Entrapment in a Virgin's Bower) and I said that this was unusual as most have pores? Well this is the more usual structure and, rather helpfully it’s been knocked about a bit (no, not by me) so we can see inside. The bits that you can see in the middle, like a set of organ pipes, are the pores. The inner surfaces of these contain the spore forming layer called the hymenium. The spores develop and then when they are ready they drop out of the holes at the bottom. The pores are connected to the core of the fungus by an intermediate layer called the context. I was going to say that the spores in the pores which are connected to the core fall to the floor but that would be out of context. So I won’t.

It seems that we can’t get any further along the stream bed because of these infernal fallen canes so it looks as though we’ll have to clamber our way out. I’ll go first and see if it’s feasible and if it isn’t you can break my fall. Seems like a good plan to me. 

Myrtle berry, Myrtus
There, wasn’t too bad was it? Up you come. Did you happen to notice that Myrtle bush on the way up? You didn’t? Can’t think why – you spent five minutes clinging onto it for dear life. In Greek mythology it was sacred to Aphrodite, the goddess of love and also Demeter, who besides being the goddess of the harvest, also presided over the cycle of life and death so Myrtle is symbolic of both love and immortality. Love life, love Myrtle so to speak. Chinese and European herbalists prescribe it for sinus infections (although the scientific jury is still out on that one), the Italians use it as a pepper substitute in their Mortadella and Bologna sausages, and the Sardinians and Corsicans make a liqueur called Mirto from it. An interesting plant from many angles, would you like to pop back down and grab a handful of berries? No? Okay then, we’ll press on.

Balkan Wall Lizard, Podcaris
Looking back, there’s no way that we were going to get through that lot so we’ll make our way back up to the track and use that as our start point next week. Oh look, a delightful little lizard welcoming us back into the sunshine. What are you doing out and about so late in the year, eh? Actually it’s not that uncommon; this is a Balkan Wall Lizard and I often see them anytime between March and November. Can you see that little hole towards the back of his head? That’s his ear. Many people think that reptiles, particularly snakes, cannot hear. That’s not true but they pick up sound vibrations in two different ways. Lizards like this have a tympanic membrane in the ear (just like us) that picks up airborne sound vibrations and also a quadrate in the lower jaw that picks up mainly surface sound vibrations. Both the tympanic membrane and the quadrate are connected to the middle ear which processes these vibrations into something meaningful to the brain. Although snakes are ‘earless’ and don’t possess a tympanic membrane they do have a quadrate that is sensitive enough  to hear us talking like this from a distance of about ten feet.3

So, bearing that in mind, we’ll wend our way back (quietly) and until next week – happy hunting..

[1] I am reliably  informed by dipterist Roger Thomason that it is a flesh fly (Sarcophaga) rather than a face fly (Musca). As you can see, the two are very similar. Thank you Roger.
[2] van der Waal's force (Wikipedia)

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  1. Sorry I was late, it's a long walk now I'm back in the UK for a while! Worth it though, or it will be once I get the myrtle out of my hair. X

  2. I was wondering where you'd got to. Don't get hypothermia up there in the Arctic wastes. X


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