Flying Ant Day

The fourth heatwave of the year arrived, the temperatures soared and the ants in one of the garden waste recycling bins took to the air in vast numbers. 

For the second year in a row ants have nested in a black 'dalek' compost bin, many of them visiting the near-by cardoon plant in July to collect honeydew from a spectacular aphid infestation. Today was the day when the temperature inside the bin triggered the emergence of a new queen, pursued by the mating flight of hundreds of large winged males.
 

Semaphore flies, with a language all of their own

 There are scores of these colourful little semaphore flies in the garden at the moment, performing their highly entertaining courtship rituals, which involve a lot of wing-waving.

Poecilobothrus nobilitatus is small but exquisite, 7mm long, with emerald eyes that burn with inner crimson fire in the sun, a bronze body shot through with green and purple iridescence and, in males, white spots on the wing tips.

The male semaphore fly’s courtship dance follows a predictable pattern. He spots a female  and a brief aerial pursuit ensues, performed with such speed and agility that it is impossible to follow with the naked eye. She settles again and he lands in front of her, white wing tips whirling in a frantic effort to semaphore his intentions, often met with total indifference. Usually, she continues to feed, rarely turning to face him. I have watched these rituals many times, and have yet to witness a successful mating. 

Sometimes two males, like those in the picture above, will face one another and, apparently, attempt to intimidate each other by vibrating their wings - but who can tell exactly what these rituals mean? Only Poecilobothrus nobilitatus can really decode this semaphore signalling language.

Sometimes the flies adopt this head-down, tail-up posture but they rarely stay still for long.

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Queen wasp mating

 Poor photo (heavily cropped, taken with an old phone in deep shade) but this appears to be a queen wasp mating with drones. They all flew away, still locked together, before I could get a better picture.

Mid-July seems very early for new queens to be leaving a nest - they usually hibernate after mating - but still plenty of summer left for her to start a new nest this year, I suppose.

Two wasp generations in one summer? Are seasonal patterns of insect behaviour confused by changing climate, maybe?

This morning, riverbank footpath, Durham city

Ants tending a herd of aphids

 For the second year in succession we have ants nesting in one of the garden waste recycling bins, which happens to be close to a cardoon plant that's hosting numerous small colonies of black bean aphids. These attract the ants because they secrete sweet, energy rich honeydew, the waste product of the sap they siphon from the cardoon. 

The ants caress the aphids with their antennae, which stimulates the aphids to produce droplets of honeydew that the ants drink and carry back to the nest in their distended abdominal segments.

In the image above and in the final image below you can see a feeding ant's swollen abdomen, rendered almost transparent where the pigmented plates of the abdominal segments have been stretched apart.

Bumblebee nest

 Buff-tailed bumblebees Bombus terrestris are nesting under a moss-covered pile of rocks in the garden. There were field mice living in the rock pile last summer and apparently it's quite common for these bumblebees to nest in their tunnels after the rodents have abandoned them.

The workers are very active and there's a lot of busy pollen collecting going on at the moment, with bees returning with full pollen baskets very few minutes yesterday afternoon.

The pollen they are carrying is orange and most of it is probably coming from this plant, Geum 'Totally Tangerine', which is in full bloom. It's an excellent bumblebee plant for species with short tongues, with open, easily accessible flowers and a long flowering period. The bees collect the pollen by working their way around the central tuft of stamens, buzzing to shake the pollen free and into their fur, they combing it into their pollen baskets.

Speckled wood butterfly laying eggs

 Speckled wood butterflies have been expanding their range northwards, into County Durham and beyond, for fifteen years now. They've been visiting our garden for about a decade and for the last five years they've been present from early spring until late autumn, so we guessed that they must be breeding here, producing a second summer generation. Last week I found proof.

A female laying her eggs on grass stems, carefully placing them one at a time.

The tiny, glassy pale green eggs provide an excellent excuse for not pulling up the grasses that are infesting the flower borders.

Do ants 'high-five'?

 

Spent a lazy hour sitting in April sunshine watching foraging ants, in constant transit to and from their nest in a big terracotta flower pot. Every time an outgoing ant met an incoming forager their stopped, head-to-head for a moment , to touch antennae, like the pair in the foreground here. Is this the ant-equivalent of a ‘high-five’? I’d like to think so, though it’s most likely colony recognition behaviour, border control, defence against potential invaders.

Winter gnats lekking on a winter afternoon.

 A freezing cold afternoon, but a swarm of these winter gnats Trichocera sp. was dancing, in a shape-shifting column, above the garden hedge this afternoon, catching the last rays of sunlight as the sun was sinking towards the western horizon. They would have all been males, lekking, attempting to catch the attention of a female.

The flower border beside the hedge is covered in a thick layer of decaying autumn leaves - just the kind of place where the females will lay their eggs.

There are come close-up pictures of winter gnats here

Himalayan balsam nectar

 Himalayan balsam is notoriously invasive and the chances of ever eliminating it on a large scale seem negligible. Even when plants are pulled up there is always a large seed bank in the soil, and flooding carries the seeds far and wide along river valleys. But it does have at least one virtue: it's a very rich source of nectar late in the year, when few native nectar-rich plants are available. Bees and wasps find it irresistible.  

The flowers have a distinctive pollination mechanism, with anthers positioned in the roof of the flower, so they deposit pollen very efficiently on the upper thorax of visiting insects, like the honeybee above and the wasp below.

Persistent insect visitors are immediately identifiable by the dense coating of pollen that they carry from flower to flower - a very efficient pollination mechanism which goes a long way towards explaining the high levels of seed production.

Some balsam nectar-addicted visitors, like the wasp above, become so heavily coated in pollen that they develop a ghost-like appearance. 

Bumblebees and poppies: do they see red?

 Human colour vision allows us to see a spectrum of colours that extends from violet to red - the colours of the rainbow - but bumblebees' colour vision is different. They can see ultraviolet, at the short wavelength end of the spectrum, but don't perceive the colour red at the long-wavelength end. But they are constant visitors to scarlet poppies in my garden, so there must be another cue that attracts them from a distance. My guess is that the lure must be a chemical one, a scent that they can detect but we can't, although the contrasting dark whorls of stamens in the centre of the flower would also  be visible to the visitor once they are close enough to see inside the flower. 

I watched this bumblebee make multiple attempts to find its way into the poppies waving in the wind, and once it found its way inside I could hear it buzzing, to shake pollen from the mass of stamens in the centre of the flower. You can see the bluish-grey poppy pollen packed into pollen baskets on its hind legs in these photographs.

Sleeping beauty awakes

 This lovely peacock butterfly must have found its way into the house, unnoticed, during the very mild weather last October, and has been hibernating here ever since. It woke up late one evening a couple of weeks ago. After settling for a while on the television screen, it flew into the kitchen and began drinking water from a damp washing-up sponge. Central heating must have made it thirsty.

 

When it settled again it performed its well-known defensive trick of flicking its wings open and closed, creating a hissing sound when the rough hind edge of the forewing rubbed against the rough front edge of the hind wing.

It might not have survived the winter in the house, either because the spiders might have found it, or if had woken again and exhausted itself fluttering against the window. So, after acclimatising it to outdoor temperatures in the greenhouse for a couple of days, I let it crawl into a large terracotta flower pot, laid on its side in the shelter of the garden conifer hedge. If it wakes again before spring there are nectar-rich flowers of hellebores and pulmonarias in the garden for it to feed on.

Bee-flies, tawny mining bees and blackcurrant bushes

There seemed to be dark-edged bee-flies Bombylius major all over the garden during most of April, either sunning themselves on stones or collecting nectar from lesser celandines, aubretia and primroses. 

These parasites drop their eggs near the nest holes of mining bees, where their larvae take over the unfortunate host's pollen store and complete their development at the expense of the bee's own offspring. The season for this activity in spring is quite short so the parasite and host's flight periods need to synchronise and the parasite needs to be able to find those egg-laying sites, which can be quite inconspicuous.

Bee-flies are restless, highly active insects that hover while the feed, and this makes them fairly easy to photograph, but they also spend a lot of time simply hovering in one spot, high above the ground, without feeding.

In our garden they almost always choose the area around the blackcurrant bushes to hang motionless in the air, sometimes for many minutes, and I've often wondered why they indulge in this energetically expensive behaviour, where they burn fuel in much the same way as a helicopter, simply to stay in one place. And what it is about the blackcurrant bushes that attracts them? It could be that  they congregate here to find mates, but they can easily do that at the floral feeding sites. 

I think the answer to why they congregate in the air above the blackcurrants is that one of the common pollinators of blackcurrant flowers is the tawny mining bee Andrena fulva, whose nest holes they parasitize. 

So could it be that this is where the bee-flies loiter to  identify their hosts, and then follow their pollen-laden victims back to their nest holes? If so, do they identify the mining bees visually - that orange fur does make them conspicuous - or is there something more subtle that gives away the host bees' presence - scent, maybe?

No easy way to answer that last question, but next spring I'll be watching again, to see if the hovering bee-flies do follow the mining bees when they leave the blackcurrant flowers and head for their burrows.

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.

Flying black ants

My daughter and her partner have a raised flower bed in their garden near Cambridge, built from old railway sleepers, and yesterday large numbers of the alate (winged) form of black ants emerged from their underground nest, for their nuptial flight. 

They swarmed on a day of classic flying ant conditions - hot, almost windless and sultry - and several hundred took to the air in the space of about fifteen minutes. These were either males or new queens, which would shed their wings and found a new colony after they had been fertilised.

These spectacular flights of black ants provide a valuable food source for birds. Fortunately there were still swifts, swallows and house martins flying around the village, be benefit from this sudden abundance of food. 

One interesting aspect of this event was that the winged ants seemed to be under attack from the much smaller workers from the moment they appeared above ground. The smaller ants constantly harassed the alates, nipping at their head and wings with their jaws,  until the took to the air. Once the winged forms were all airborne the workers disappeared below ground again.

A few of the winged forms seemed to be weakened or killed by the attacks.

In this image you can see a worker gripping an alate's wing with its jaws.