Sunday, September 22, 2019

Wasp vs. Hoverfly: no contest

Here's something I've never seen before - a common wasp killing a hoverfly. They both landed in a rose flower at the same moment and immediately there was a fierce tussle, as the wasp grabbed its prey. 

Then the wasp bit off the hoverfly's head by chewing through its joint with the thorax. Strange behaviour because at this time of year there will no longer be any grubs for the wasp to feed in the nest, and when the nest begins to break up wasps tend to focus on sweet liquid food, like nectar and rotting fruit, rather than on live animal prey.

Thursday, September 19, 2019

A butterfly haven in an old limestone quarry

This is Ashes quarry, a former limestone quarry near Stanhope in Weardale that is now a wonderful nature reserve. The quarry floor is partially flooded and is a breeding place for dragonflies and damselflies, but this sheltered western end, which is mostly rough grassland and quarry spoil heaps, is always a good spot to look for butterflies.

It was good to see a small colony of wall browns has become established here. This is a butterfly that needs warmth and shelter, so this sun-trap, with its sun-warmed rock, clearly suits it very well.

Wall browns are very skittish insects, never settling for long in one place. This individual alternated between basking on its pile of rocks and feeding on herb robert flowers blooming amongst the stones.

The convenient supply of floral nectar meant that this one was constantly disturbed by rival males that tried to take over its domain. Wall browns are ferociously territorial, so each one of these incursions resulted in an aerial dogfight, as the butterflies spiralled upwards, so close to me that I could hear their wings clashing, before they separated and fluttered back to their respective territories.

Eventually a female arrived and courtsship began, with the pair walking through the grass and the male tapping the female with his antennae. I think the male is the closer of the two in this picture, with some wing edge damage that might have occurred during one of those bruising dogfights with a rival.

Wall brown colonies tend to be small and don't often persist in the same place for long, but this quarry site is sheltered and warm, with plenty of the caterpillar food plants (grasses), so it might last for a few years.

The warm piles of stones in the quarry are also excellent habitat for sun-basking common darter dragonflies ....

..... chirruping field grasshoppers Chorthippus brunneus

..... and this devil's coach-horse Ocypus olens. This beetle (more pics here) isn't often seen out and about in bright sunlight - it's more often seen in twilight.

Saturday, September 7, 2019

Chilled roe deer

Most of my encounters with roe deer have been brief - often just a bobbing white tail disappearing through the trees. But this one, near Romaldkirk in Teesdale, was different: we stood, looking at each other for a couple of minutes, before the deer slowly turned away and ambled into an old hazel coppice. 

One of those privileged encounters I'm likely to remember for a long time, on an early autumn day when the sunlight showed off to perfection the beautiful coat of this gentle animal.

Tuesday, September 3, 2019

Fatal attraction, to yarrow

Yarrow Achillea millefolium is a later summer wild flower that provides easily-accessed pollen and nectar for visiting insects, right up until the end of autumn. It's particularly popular with flies, like this greenbottle, and with hoverflies and droneflies. They can feed without expending much energy, simply by landing and walking from floret to floret across the flat-topped umbel.  

But sometimes just landing on the flowers can be hazardous. About thirty yarrow plants were hanging over a wall along Mortham Lane beside Rokeby park in Teesdale. They had been blown sideways by high winds during their early growth, and at the same time their flower heads had defied gravity and curled upwards, so the whole plant protruded from the wall like a long coat hook. And in that hook, in every plant, a money spider had built its hammock-shaped web, beside the flower head. Money spiders usually sling their horizontal hammock webs in hedges or low in the grass, but this population had taken advantage of the yarrow scaffolding that an accident of wind and gravity had provided.

I watched these plants swaying in the wind, while a long procession of insects came to feed. Drone flies are skilled hoverers and negotiated the risky landing successfully, and .....

.... hoverflies timed their approach and landing with even more precision, avoiding the spider's snare. But there was plenty of evidence, in the form of wings and legs in the webs, that other flies had been less fortunate, and had made a fatal landing in the money spider's web. I saw a blundering greenbottle land in the web, but with good fortune and some frantic buzzing it just managed to extricate itself before the spider arrived.

And in this old web a well-fed occupant had evidently done enough feeding, and had woven its egg cocoon amongst the leaves below the flower head, that had acted as bait for its victims.