Friday, July 20, 2012

The Shining: Part Two

Having been blown away by the rear-end wiggle-walk antics of glow-worm larvae in May (see videos in my previous blog), we were jolly keen to return to Elham Park Wood to find some glowing adults.

So in late June, on a cool but dry evening, and after a thoroughly agreeable picnic tea amid fragrant orchid profusion at Park Gate Down, we retraced our steps in the woods. As evening fell and as our eyes grew accustomed to the lack of light, we saw wonderful things; little blips of light started appearing, like magic, in the grass next to the path. The glow-worms were glowing :-)))

I didn't want to use flash or a torch so here's the best close-up I could get.


This is a female glow-worm (OK you can only see her rear end) advertising for a mate. You'll recall that glow-worms spend about 2 years as carnivorous larvae, then in their final summer, they become adults for a few short weeks (during June/July). They don't feed as adults, they just mate, hopefully reproduce, then die. Adult glow-worms are sexually dimorphic with the females being flightless and rather similar in appearance to the larvae. The males fly and find their mates using phototaxis (movement in response to light) (Booth, Stewart & Osorio 2004). Here's a rather good photo of a male from Wikipedia.

Male glow-worm by Hectonichus, 2007, taken in Italy and used here under a 
Creative Commons Attribution-Share Alike 3.0 Unported license.

It's a magical experience lying on a cold, damp gravel path in the middle of a dark forest gazing at a little insect wiggling its bioluminescent bottom. I can't recommend it enough.


Time for a joke?
A glow-worm walks (make that 'wiggles') into a bar.
Bar-tender says 'What can I get you mate?'
'I'll have a light ale please.'

Enough of this light-hearted humour. Back to ecology. So, how does a glow-worm glow? Glow-worms are bioluminescent; able to produce and emit light via a internal biochemical reaction (literally it means living light). I was going to summarise the biochemical processes involved but Dr John Day does an excellent job of that here. It's all catalysed by the marvellously useful enzyme luciferase, which is named after Lucifer, the 'light bringer'.

Once the females have mated successfully their glow diminishes. Their job done, they die soon after laying eggs. Larvae do apparently emit a low glow, which we looked for in May but didn't see.


These ladies do not just light up their behinds and sit there. On no. These girls know how to move. They wiggle their rear-ends alluringly. You can just about make out some of their 'come and mate with me' grooves in my poor quality video.

video

As with so much wildlife on our crowded isle, glow-worms have decreased in numbers over the past decades. They are rarely found on 'improved' agricultural land, preferring less disturbed grassland. They are most 'common' in the south on chalk grassland (Gardiner, 2009). As glow-worms are unable to move to colonise new areas (the females are flightless) their numbers have declined as habitats become fragmented and, in some cases neglected (Gardiner, 2009).

Development and light pollution are ongoing threats to glow-worms. A recent study from the University of Southampton is concerning, finding that low levels of light pollution (lower than previously thought) can reduce the effectiveness of glow-worm reproductive signals. Males were unable to locate females in even dim artificial light, because the female's signal is drowned out (Bird & Parker, 2011). No wonder we've only found glow-worms on dark woodland rides......

Like Sir David (quoted this week in an article in the Indie) I'm generally rather pessimistic about the future for our wildlife and natural habitats. So many pressures on land from so many people. And a government uninterested in sustainability (see George Monbiot here for an acerbic take on Rio+20 and the evolution of 'sustainability' to 'sustainable development' to 'sustainable growth', an entirely different concept to the original). 

How many people have seen a glow-worm glow? Perhaps Sir Winston Churchill did. Here's a quote attributed to the great statesman; 'We are all worms, but I do believe I am a glow-worm' (see Bonham-Carter, 1965).

Further Information and References

Bird, S & Parker J (2011) Low levels of light pollution may block male glow-worm’s (Lampyris noctiluca L.) ability to locate females. Journal of Insect Conservation. Abstract only here.

Bonham-Carter, Violet (1965) As I knew him. London: Eyre & Spottiswoode and Collins

Booth, D Stewart, AJA & Osorio, D (2004) Colour vision in the glow-worm Lampyris noctiluca (L.) (Coleoptera: Lampyridae): evidence for a green-blue chromatic mechanism. Journal of Experimental Biology. Volume 207, pages 2373-78. Abstract here and editorial here.

Gardiner, T. (2009) Glowing, glowing, gone? British Naturalists’ Association, Corby. Full pdf here.

An early account of glow-worm natural history is by George Newport (1856) On the Natural History of the Glow-worm (Lampyris noctiluca). Journal of the Proceedings of the Linnean Society (Zoology). Volume 1, Issue 2, pages 49–71. Available online here. An even earlier account from a 1793 volume of The Gentleman's Magazine is here.

This looks like a super new book which I'd like to read when it's published in 2013; Dr. John C Day 'Fireflies & Glow-worms'.

BUT....if you want to know more about glow-worms go no further than Robin Scagell's excellent site. If you see a glow-worm you can send him your record via this website: http://www.glowworms.org.uk/

6 comments:

  1. Hello Mel,

    I saw a glow-worm at the foot of the railway bank here in Flitwick (Beds) last July and sent a report to Robin Scagell. He replied requesting that I look on Flitwick Moor, where somebody had reported seeing larvae, but I couldn't find any there. They used to be quite oommon on the railway bank until about 20 years ago. Perhaps they are less common now because trees and brambles are beginning to take over? Not seen them this year (OK...I won't mention the weather, but it's been my worst ever summer for honey),

    As an aside, I did a long-planned walk from Hastings to Rye yesterday afternoon. I saw lots of Ivy-Leaved Toadflax, Clematis and Woody Nightshade on the shingle near Rye Harbour, as well as the "usual suspects". Are these common at Dungeness also? There were Cladonia sp. and other lichens on stabilised shingle just behind the top of the beach, often associated with a plant whose hairy leaves reminded me of Mouse-Ear Hawkweed. Buellia aethalea was also growing there directly on pebbles. However the best area of stabilised shingle for lichens that I saw was close to Rye Harbour church (where there is a danger of brambles taking over). I wondered why there are sand dunes on the east side of the harbour but not the west and whether these would be worth exploring for lichens, but I didn't have a boat to cross the water - another day perhaps? I was interested in the newly created "saltmarsh" on the nature reserve. I wonder if anybody is monitoring plant colonisation there? The adjacent established saltmarsh next to the Rother was interesting with the usual Sea Puslane and Sea Aster in the wetter parts, Sea Wormwood higher up and Sea Couch on the bank above, but I was surprised not to see Sea Lavender, which is very common in N. Norfolk. Does it occur in other saltmarshes in Sussex and Kent, or did I miss it becasue it has finished flowering I wonder? However, highlight of the day was the half dozen starfish I saw in a sandy pool near a groyne near Cliff End - I've never seen them in N. Norfolk. I would like to have spent more time exploring this facinating area, but my feet were sore and I had a train to catch.

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    1. PS I meant to add that glasswort seems to be the first coloniser of the new salt marsh at Rye.There's several species of glasswort and I suppose they each have their own niche. In N. Norfolk, one species seems to be a pioneer of muddy sand in the middle to upper part of beaches, trapping silt and beginning the process of salt marsh formation.

      I should also have said that coast path from Hastings to Fairlight is highly recommended, with wonderful views of the cliffs and the rocky shore below and of the coast from Beachy Head to Dungeness (and also Cap Gris Nez, across the channel). Oak woods above Fairlight Glen are rich with lichens and there are liverworts by the stream, and the beach below is lovely for paddling and exploring rock pools if you don't mind sharing it with naturists. It's quite a strenuous walk, but there's a good pint of Harveys to be had in Hastings near to the steps at the start to provide energy for the climbing and another at Cliff End to aid recovery afterwards.

      Thanks for your lovely new blog, Mel, and for sharing your pictures, insights and research with us.

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  2. Enjoyable blog - I hope you'll be posting again soon?

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  3. Glow-worms are a magical sight. They are supposed to inhabit grasslands, but at At High Elms they live mostly in the woods, where I have seen them glowing under the trees, and that's where you seem to have found them too. Good photos and an enjoyable report!

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  4. Hi Bill. Yes I too had it in my mind they were grassland critters, but my best sightings this year were on woodland rides.

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