Thursday, August 3, 2017

Golden-ringed dragonfly


Dragonflies are the subject of my Guardian Country Diary today.

This is the peak period locally to watch these spectacular gold-ringed dragonflies Cordulegaster boltonii, which have the longest body (but not the greatest wing span) of any UK species. We discovered this female in the early morning, torpid after a cool night, resting on a patch of rushes next to a footpath.
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There are several prime locations for this impressive insect here in the North Pennines. One of the best is in Hamsterley forest, near Spurleswood beck, which has the kind of crystal clear, highly oxygenated water and stony stream bed that forms a perfect breeding habitat. Another is along the river Derwent near Blanchland in Northumberland. A third is in Weardale, in a shallow stony beck that runs down the hill into the top of Tunstall reservoir near Wolsingham in Weardale.














While I was photographing this individual she began to warm up her flight muscles, first with just the merest hint of a vibration in her wings, until she was like a helicopter on the verge of take-off. Then she let go with those legs, which are of little use for walking but are used for gripping perches and catching prey in mid-air ..... and she was gone, hunting flies over the bracken.















The marvels of dragonfly vision are almost beyond our comprehension. We have trichromatic vision, with sensors that detect red, green and blue, which together define our visual spectrum. Dragonflies have sensors that detect at least five wavelengths, in addition to ultra-violet which is beyond our perception, and some species have thirty sensors that each detect a different wavelength, so their colour spectrum is vastly more complex and subtle than ours.

It's an interesting thought that those bright colours that we admire when we watch a dragonfly are not the colours that they see.

Then there are those massive compound eyes, each composed of thousands of separate facets (ommatidia), which give them highly sensitive flicker vision. When fast-moving objects cross their field of view they are tracked by a succession of ommatidia that convey the information to the brain.

Their amazing eyes, coupled with their speed of flight and extreme manoeuvrability, make them deadly aerial interceptors.



Saturday, July 29, 2017

Some early Amanita toadstools - another symptom of a warmer world?


It seems strange to be blogging about toadstools like these in July ....... I can't recall seeing either of these in Weardale quite this early in the year. Both were photographed yesterday in Backstone Bank wood near Wolsingham in Weardale. There were also numerous larch boletes Suillus grevillei in the larch plantation and some slippery Jacks Suillus luteus amongst the Scots pines, mostly eaten by slugs.
























Grey-spotted amanita 
Amanita spissa

























Fly agaric 
Amanita muscaria

There is now quite a substantial body of evidence that fungi are fruiting earlier as a result of climate change, and in some cases fruiting in spring and autumn. Various reasons have been suggested, including one that mycorrhizal fungi like these (which form a symbiotic link with tree roots) are receiving more nutrients from the trees that now have a longer growing season. Another is that decay rates in forest soils are increasing as average temperatures rise.

A major survey at Cardiff university in 2007 revealed that some species are fruiting for much longer, with an increase in some species from 33 days in the 1950s to over 75 days.

Maybe summer fungal forays will become commonplace in future.

You can read more scientific research about the links between climate change and fungal fruiting times by clicking here and here and here and here

Sunday, July 23, 2017

Moss pop-guns


It's not very often that I find bog moss (Sphagnum) bearing spore capsules. They are easy to overlook because they are not raised on a long stalk (seta) like the capsules of many other British mosses.
















I found these on cushions of Sphagnum growing in a little hillside mire near Wolsingham in Weardale. I'm wondering whether it may have been the very dry spring followed by wet mild weather that triggered rapid growth and their formation.

The capsules remind me of small, round ginger jars.

They are unusual because, unlike most moss capsules that shake spores out through pores or peristome teeth, these literally explode.














As the capsules mature they lose water and the air inside them becomes pressurised. As the walls contract the capsules change shape, from spherical to cylindrical like the rearmost in this photograph. Eventually the lid blows off, sending a mushroom cloud of thousands of microscopic spores, in a vortex like a smoke ring, about ten centimetres into the airstream.

You can watch a high-speed film of the whole process by clicking here and here  


Saturday, July 22, 2017

Harvestman


It's a sign of the high summer when harvestmen appear in our garden. Initially I though this was Leiobunum rotundum, until Richard Burkmar (see comment below) pointed out that it's an invasive, non-native species called Opilio canestrinii which was first documented in Britain in 1999.This species has remarkably long black legs, like L.rotundum, but there is an orange ring around the trochanter ('knee') that I hadn't notice. This male, sunbathing on a leaf in the late afternoon sunshine, is in pristine condition, probably having just reached maturity. Females have a darker saddle-like marking on their dorsal side.



































The longest legs are the second pair and key senses of taste, smell and touch are located on these. If you watch them walking through the undergrowth you can see them using these to explore their surroundings.

Harvestmen often lose a leg of two, shedding them if they are grabbed by a bird or caught in a spider's web, and this isn't too much of a problem unless it's the second sensory pair - then they are in more serious difficulties.

For more harvestmen (including pictures of a female Leiobunum rotundum) on this blog, click here.





































Opilio canestrinii has spread northwards quite widely since it was first found in Essex eighteen years ago. The Spider and Harvestman Recording Scheme web site (click here) shows that it has reached as far north as Inverness. 

My guess is that it arrived in our garden via a plant from a garden centre. The wholesale and retail garden plant trade provides perfect distribution network for newly arrived arthropod species like this.


Friday, July 21, 2017

A very hairy gooseberry


All over the North Pennines there are traces of small settlements - usually mining communities or sometimes farmsteads - that have long since fallen into ruin. In some cases all you can see is a few piles of stones and the rectangular outline of building foundations, but often you can also find botanical traces of past gardens.

The commonest edible plants in these are rhubarb and gooseberries, which persist for generations, long after the gardeners who originally planted them have been forgotten. At this time of year the gooseberries start to ripen and I always make a point of tasting these, which mare mots likely to be forgotten varieties that are no longer cultivated. There are also scattered bushes well away from gardens, that would have been bird-sown. There is a large gene pool of feral gooseberry varieties out there in the countryside and maybe there might even be some that are resistant to diseases like gooseberry mildew.

This unusually hairy example was growing through an old wall in Teesdale and ripens to a deep ruby red. Its fruits are exceptionally sweet, though you need to rub off those hairs first it you want to eat it uncooked. It probably closely resembles the wild species that originated in continental Europe and which lost most of its bristles during cultivation.  If it was stewed or used to make chutney (gooseberries make excellent chutney) then they wouldn't matter too much.

I've rooted a cutting of this one, that's now growing in my garden. 

Apparently, gooseberries were first domesticated in the Middle Ages and there are records of plants being imported from France in 1275 for planting in Edward 's garden in the Tower of London.

Growing goooseberries competitively, to see who could produce the largest fruits, became popular amongst Lancashire weavers in the 1740s and the heaviest fruits weighed in at over 50 grams, over seven times the weight of the wild ones. By the early 1900s almost 1000 named varieties existed, cultivated by gooseberry clubs.

There is still an annual gooseberry growing championship at Egton Bridge near Whitby in North Yorkshire, which you can read about by clicking here. This year's show is on 1st. August.

The world record currently stands at 62 grams. 



Thursday, July 20, 2017

Soundtrack to Summer


Today's Guardian Country Diary is about grasshoppers.

These lovely insects, that provide a soperific soundtrack to late summer, are sun-loving so their greatest species diversity in the UK is concentrated in southern England.

We have two common species here in the North Pennines ......















... the green grasshopper  Omocestus viridulus....






















.... and the meadow grasshopper Chorthippus parallelus.

Both 'sing' by stridulating - dragging those pegs on their hind femur over the hard edges of the wing. The meadow grasshopper has the most varied song and both sexes chirrup, though the female's song is quieter than the male's because those stridulatory pegs tend to be smaller in females.

Males have three distinct songs - a loud one for attraction, a quieter one for courtship and a stucatto one during mating. 















They can be hard to spot because they are well camouflaged amongst dry grasses and heather, and on warm afternoons their -leap-flutter-glide escape technique can make them hard to catch.














Grasshoppers hatch from overwintering eggs as a tiny worm-like organism that then undergoes four moults as the nymph grows. This is a meadow grasshopper in the  penultimate instar before becoming an adult - it still has wing stubs but these will reach full size during the next moult. 
















This female, sitting in the sun amongst bell heather, has lost her hind leg on the left-hand side. Nymphs in early instars can regenerate lost legs but this one must have lost the limb after becoming an adult, perhaps to escape the grip of a bird's beak.

Surprisingly, there are documented instances of grasshoppers that have lost a hind leg being able to stridulate and respond to a mate's song with the remaining limb. The impediment must make for lop-sided leaps though!


Sunday, July 16, 2017

cocksfoot vivipary

Cock'sfoot grass Dactylis glomerata sometimes exhibits unusual reproductive behaviour, known as vivipary.





































This is a normal inflorescence, with florets that will produce seeds after pollination ....



































..... and this is an abnormal inflorescence that I found a few days ago, where florets have started to form but have no stamens, stigma or ovary and the bracts that surround these structures have become leafy.

This viviparous behaviour is commonest in late-flowering plants and what has happened is that during their development the flowers have become leafy vegetative structures. 

The assumption is that these will eventually drop off, form roots in contact with the soil and grow into new clonal plants that are identical to the parent. 

I've never sen any evidence that these leafy structures are really capable of rooting and forming new plants, so ....




































..... I'm keeping a close eye on them to see if it really happens. So far, after four days, those leafy bracts are growing, but so far no sign of any roots....

Friday, July 14, 2017

A regurgitated corvid food pellet

Although owls and birds of prey are best known for regurgitating pellets of indigestible prey fragments, other birds - including herons, gulls and members of the crow family - also produce similar but smaller pellets.




































This one, which I found on a fence post today, was most likely produced by a crow, magpie or jackdaw. At the front of the pellet you can see a crane-fly wing.


















If you look closely you can see that much of it is made up of chitinous fragments of insect exoskeleton. There are broken pieces on what look like beetle elytra in there but are also crustacean remains, in the form of the tail segments of a wood louse (the white material just above the centre of the picture).


Thursday, July 13, 2017

Shield bug


Red-legged shieldbugs Pentatoma rufipes are very numerous hereabouts at the moment, often sunning themselves on oak leaves.





















Shieldbugs generally feed on plant sap by piercing leaf veins with their pointed mouthparts, though they will also eat slow-moving animal prey like caterpillars.

This one had taken a liking to feeding on a bird dropping, which is likely to be a good source of minerals. Many insects, including butterflies, will eat animal excrement as a source of calcium that they need for egg laying.






















The grey patch just above the middle leg here is the site of the stink gland, which produces a nauseating fluid that deters predators.
























The Field Studies Council publishes this excellent fold-out identification chart of shieldbugs. They're an interesting group to study because a) they aren't difficult to identify b) there aren't too many species, and c) they are quite slow-moving, so they are easy to watch and photograph.

There is also an excellent web site called British Bugs devoted to all the hemipterans, including shield bugs, which can be accessed by clicking here.

Tuesday, July 11, 2017

Ringlets


It's peak flowering time for brambles in Teesdale at the moment, which means that it is also peak feeding time for ringlet butterflies Aphantopus hyperantus that like to nectar on the flowers.















When they first emerge their wings are like dark brown velvet, fringed with white hairs, but as the season progresses they lose scales and their colour becomes paler. 
This individual with nicely defined wing spots, sunning itself on a bramble leaf today, is a female. Males tend to have just small dark dots as wing markings.























Ringlets have become much more common in the North Pennines over the last thirty years. There is no shortage of their larval food plants - grasses - and the adults seem very tolerant of dull and damp conditions. I've often seen them flying low over vegetation in very overcast conditions and sometimes even in drizzling rain.

They are very casual about where they lay their eggs. Most butterflies stick them on their larval food plants but ringlets just drop them into the grass. 

Purely by chance, a few years ago I photographed this one in the act of laying an egg, with the egg in mid-air.

Friday, July 7, 2017

Drizzle


Wednesday dawned with the kind of leaden skies and grey drizzle that makes you want to stay under the duvet all day. But windless mornings with fine drizzle can work magic in meadows.

We are only a week or so away from the main period of haymaking in Weardale and Teesdale and the meadow grasses are in full flower. When that coincides with drizzly, foggy weather and there is not a breath of wind every grass floret catches a jewel of water and every grass stem is laden with rows of water droplets. One puff of wind and the effect would be ruined, but for a short time it is exquisite.

Definitely worth getting out of bed for!







Thursday, July 6, 2017

Froglets


We've had to watch our step in the garden during this week's wet weather, because the tadpoles in the pond have been metamorphosing into tiny froglets that are about the size of my thumbnail.  They would be so easy to tread on. Still, it's a great excuse for not mowing the lawn, as they seem to spend a lot of time in the grass.















A tiny froglet like this has a lot of growing to do before it reaches reproductive age. When they are this size they are prey for birds and perhaps even larger ground beetles and centipedes





































They need to adapt quickly to their change in buoyancy during the last days before they leave the pond. Tadpoles absorb oxygen dissolved in water via external gills and over their skin surface and if they stop swimming they sink, but once they become froglets their internal lungs take over and the air inside their bodies makes them float to the surface to gulp more air. 

This one seems to be just chilling, floating with only its nostrils above the water. 





































At this stage the froglets must be able to climb out of the water but ...
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...... when they first metamorphose they are light enough to sit on the water surface.

There is often one important hazard that froglets face when they try to leave ponds that are surrounded by paving on warm, sunny days. Dry paving stones can become very hot underfoot and I have seen froglets perish in their attempts to cross them, so an area of grass around a pond that reaches down to the water surface offers a much safer escape route.