November 2017

My apologies for rattling on about spiders again, but it does seem to have been a particularly good year for our eight-legged friends.  (Of course they are friends, they keep the fly population under control.)  We recently came home to find a garden spider (the one with the white cross on its back) apparently floating in mid-air.  It was, on closer inspection, in the centre of its web, but it was still way above the hedge and surrounding shrubs.  This spider, clearly dissatisfied with the diet obtainable by building a web between shrubs, had climbed the telegraph pole and suspended its web from the telephone wire.  This is as good a demonstration of spider planning and intelligence I’ve ever seen.

Garden Spider

I recently had a trip out to Aberdaron in North Wales where I was struck by the variety of wildflowers still in flower in mid-October.  The trees were starting to lose their leaves there but there was plenty of clover and knapweed in flower.  One particular species stood out - Common Fumitory.  There are only a handful of species of fumitory found in the UK and they are in a very small sub-family called fumariaceae.  I was quite surprised to find that fumariaceae is a sub-family of the poppy family, mainly because of the huge difference in the shape of the flowers.  Apparently they got the name fumitory from the smoke-like appearance of the plant with its grey-green leaves.  It is a certainly a very delicate plant with its fern-like leaves, though I would have called the leaves bright green.  An alternative name for the plant is earth smoke, though to appreciate the smokiness, perhaps you need to get up early when there is dew about and maybe squint a bit. The scientific name for common fumitory is fumaria officinalis.  Plants with officinalis in the name were normally used as herbs or medicines and fumitory is still used by herbalists to treat skin blemishes and conjunctivitis.  Interestingly common fumitory is a source of fumaric acid, which is something human skin produces when exposed to sunlight.  It is also a food additive, often shown in the ingredients list as an acidity regulator and has the E-number E297.  And if you have a taste for salt and vinegar crisps, then the vinegary flavour probably comes from fumaric acid.

Common Fumitory

One consequence of the late flowers is that the insects that depend on nectar are still about and we saw several red admiral butterflies.  This species used to be a migratory species.  Eggs were laid in Southern Europe or North Africa and several generations worked their way northward, arriving in the UK in late spring.  As the weather gets colder in autumn, they then fly south to over-winter and start the cycle again.  But now, with milder winters, there is less pressure to return south and so we now find that some red admirals hibernate here and together with the migrating population swell the total population in the UK.  A sister species of the red admiral is the painted lady which also migrates northwards from Africa and the mystery there was that nobody saw them flying back southwards.  It wasn’t until 2009 that investigations of insects using new radar techniques discovered that they do fly south but at altitudes of over 1000 metres (about 3,300 feet in old money).  The migration(at speeds of up to 30mph in favourable winds) involves a round trip of more than 9,000 miles and six generations of hungry caterpillars. 

Red Admiral

This is a much longer migration than the better known migration of monarch butterflies from Mexico to Canada.  So next time you see a red admiral or a painted lady you can marvel not just at their beauty, but also at just what a tough creature it really is.

Painted Lady

October 2017

Warning: This article makes reference to creatures with eight legs.  Well now that we’ve lost the arachnophobes we can talk about creatures that at this time of year suddenly seem to be everywhere.  They have, of course, been everywhere since the spring, it’s just that now they are much, much bigger, and consequently they build bigger and stronger webs to catch bigger meals for themselves.  And talking of size – now that the arachnophobes have gone – the average person is at least 150 times taller than the biggest UK spider, and at least 30,000 times heavier, so what’s the problem?  Having said that, however, I have seen some sizeable spiders recently.  On a recent survey at Rye Harbour I found a four-spot orb-weaver spider and two very impressive wasp spiders.

The four-spot orb-weaver was a large female with a brick-red abdomen that accentuated the four white spots on her back – a real beauty.  She had just caught a turnip sawfly and was injecting venom into it as I was taking photographs.  She had a very large abdomen that suggests that she was carrying a heavy load of eggs.  It has been found that a female with her egg load can weigh as much as 2.5 grams, and that after laying her eggs into the protective cocoon that will keep them safe until the spring, she only weighs 0.8 grams – less than half the weight of her eggs.  After the sawfly had been subdued, it would be eaten.  Unlike most other spider species that inject digestive fluids into their prey, and then suck out the resulting ‘soup’, the four-spot orb-weaver chews its prey and doesn’t leave the empty husk.  One bizarre fact I discovered while fact checking for this column was a quote from a research scientist who had done a spider taste test and found that… of the spiders tasted that day, ‘the four-spot orb-weaver – with a slightly nutty flavour – was the best’!

The turnip sawfly is part of the Hymenoptera family that includes bees, wasps and ants.  Like bees, the turnip sawfly adults feed on nectar and pollen, but unlike bees, wasps and ants, they don’t have a sting.  They get the name sawfly because the females have an ovipositor with a serrated edge that is used to cut into the plant stems in which they lay their eggs.  The turnip sawfly is bright orange with a few contrasting black bits – one of nature’s most reliable warning signs.  So if they don’t sting, why the bright colours?   It’s called a turnip sawfly because the larvae feed on brassicas – like turnips, cabbage, etc.  Brassica leaves contain substances called glucosinolates that give the leaves a bitter taste to discourage insects from eating them (and possibly to give children a reason to dislike sprouts).  But the sawfly larvae ingest the glucosinolates and concentrate it in their blood.  This can then be released in foul-tasting droplets to try and prevent predatory insects from eating them.  Even though the adult turnip sawfly doesn’t eat turnip leaves, its blood still contains the glucosinolates, hence the ‘don’t eat me I taste horrible’ colours.  Sadly for the turnip sawfly in the four-spot orb-weaver’s web, the spider ignored the warning.