The Spiders and The Fly

Today's Guardian Country Diary describes a walk along a stretch of the banks of the river Wear at Wolsingham in Weardale, along a footpath known as The Fly. The name probably refers to the fact that this is a good stretch of fly fishing river, but it's also a fine place for finding interesting insects and spiders.

The early part of the walk passes through meadows like this one, which have produced a wonderful display of buttercups this year. This might be because the buttercups, which store starch in their roots over the winter that can be used for rapid growth in spring, have responded to the unusually late spring by growing more rapidly than the grasses.

Then the path plunges into shady woodland with dense vegetation on the edge of the river .......

... before the trees - mostly alders along this stretch - thin our. At this point the soil is mainly fertile silt left by winter floods and the vegetation is luxuriant - these aniseed-scented sweet cicely plants were head-high. If you click here you can see what this spot looked like back in May, when the tallest plants were only ankle-high.

A crane-fly, showing the paired balancing organs rather nicely.

There were a many of these snipe flies Rhagio scolopacea (above) lurking in the last of the hawthorn flowers that bloomed almost until the end of June in the hedgerow along the first part of the path. They're predators, flying out to catch passing insects. Snipe flies have a distinctive habit of resting in this head-down posture in hedges. Those unusually large eyes are exceptionally sensitive to movement of prey passing through their field of vision.

The dense riverbank herbage is perfect habitat for these scorpion flies Panorpa communis. The curled up tail, which looks dangerous, is really the male's specialised genitalia.

Scorpion flies belong to a very ancient order of insects called the Mecoptera and fossils of their distinctive wings show that they evolved at least 250 million years ago. They are thought to be the ancestors of butterflies, moths, caddis flies and true flies. 

The two pictures above are of a female, which lacks the 'scorpion' tail of the male.

Bird cherries are a prominent component of the tree flora here and some have become infested with small ermine moth caterpillars, which weave a silken tent where they can defoliate the tree in comparative safety ....

... although this one has broken cover.

In years when there are heavy infestations whole trees can be enveloped in these silk tents.

There's a diversity of fly species along this footpath - and also plenty of spiders. The three pictures above show the cucumber-green Araneus cucurbitinus, whose abdomen can look like a flower bud. It weaves its snare across the surface of leaves.

This, though, was our most fascinating spider discovery - a ball of recently hatched diadem spiderlings (aka orb web spider, aka garden spider) Araneus diadematus. At this stage they huddle together for mutual security but if you give this seething mass of tiny arachnids a gentle poke .....  

...... the spider-ball explodes and they scatter in all directions.......

... racing away along the silken threads that suspend the ball ....

.... like sailors climbing the rigging of a sailing ship.

Orange tip caterpillars

Back at the beginning of June orange tip butterflies were laying eggs on Jack-by-the-hedge (aka garlic mustard, aka hedge garlic) in our garden and since then the caterpillars that hatched have been doing pretty well.

In their early stages the tiny caterpillars are pale yellow but after a couple of weeks ....

.... they become grey-green and are quite well hidden when they align themselves with their host plant's seed pods. At this stage the prominent hairs on their segments are each tipped with a tiny droplet of secretion, which I suspect is something that repels potential parasites, like ichneumon flies. It doesn't deter wasps though, which I have watched carrying away small caterpillars. I once watched a wasp chew a larger orange tip caterpillar in half and then carry each bite-sized chunk back to the nest.

All the butterfly books mention the cannibalistic tendencies of orange tip larvae, and the way in which this butterfly only lays one egg per inflorescence, but this year I've seen several hedge garlic plants with two or even three caterpillars eating seed pods in what was the same inflorescence, where the butterfly must have laid multiple eggs. I wonder whether this was due to the late flowering of the host plant and the need for the butterflies to lay a lot of eggs quickly. It may be that they are more likely to do this in plants like hedge garlic that produce a lot of large, succulent pods, unlike the alternative and much smaller food plant lady's smock, where the food supply from each inflorescence is much less.

A caterpillar like this, that's approaching maturity, easily demolished one of these three inch-long hedge garlic seed pods in a day. Then, when they are fully fed, the larvae vanish, crawling away to pupate. We've had a thriving orange tip colony breeding in the garden for many years and I have only once found a pupa, suspended from a dead plant stem by a silken halter and extremely well camouflaged, with an outline that resembled a thorn.

A butterfly bank: second visit

About a month ago I posted some pictures of a beautiful magnesian limestone embankment along an old disused railway line at Trimdon near Durham city. This weekend we went back for another look and the flora was even better.

The viper's bugloss, which was only rosettes of leaves on our last visit, had now produced tall spires of flowers.

At the moment, this is just about the most flowery spot I know, with ....

...... bladder campion .......

...growing here with viper's bugloss ....

..... intensely fragrant burnet rose ......

..... eyebright, a plant that's partially parasitic on the roots of other plants....

..... greater knapweed .........

....... rock-rose .....

... and common spotted orchids that were too many to count, with numerous variations: this is an albino form.

Twayblade orchids, that are well hidden amongst the background vegetation..........

... and drifts of viper's bugloss, which bees can't resist.

Wild strawberries ..........

....... and wild thyme.

Magnesian limestone flora at its best!