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.
 

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.

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.

Ants in the compost bin

 We've been composting garden and kitchen vegetable waste in 'Dalek' bins like this for decades, but this year was the first times that we've had one taken over by nesting black ants. 

They moved in during those unusually cold weeks of early summer, probably because the warmth of decomposition in the bins provided the only location in the garden with enough heat for them to breed.  Textbooks say that they need a temperature of 10C to become active and 20C to raise a brood.

Watching their progress in the bins has been fascinating because the temperature inside rises very rapidly when the sun comes out and falls equally rapidly on dull wet days and in the evening, so they seem to be constantly moving their brood around to the optimum positions in the bin. At one point I thought they had left, but it seemed that they just moved their larvae and pupae deeper into the compost, in a cooler part of the bin. They shift their brood with remarkable speed when I lift the lid and light floods in - they can move a couple of hundred pupae, by carrying them in their jaws, in a few minutes.

Their larvae are translucent, but as they  pupate they spin a silken coat.

Lately, winged males have started to hatch so before long a queen will take to the air, followed by a swarm of males on the nuptial flight. After mating she will start a new nest, while most of the males will become food for swifts that swoop over the garden. 

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.  

Ants 'farming' aphids

We found these ants 'farming' aphids on a ragwort plant when we were out walking in the Tyne valley near Wylam this morning.

The ants gently stroke the aphids with their antennae, to encourage them to excrete honeydew that the sweet-toothed ants collect.

I suspect the aphids are ragwort aphids Aphis jacobaeae, but I need to get that confirmed by someone on iSpot. Also need an ID for the ant species.

Ants as nectar thieves and pollinators

I've seen ants visiting small flowers before (like this one visiting sea milkwort) but I didn't notice the ant on this heath bedstraw until I knelt down to photograph the plant .....

..... it's just above and to the right of centre in the picture.

 On closer inspection it was clear that I wasn't just a casual visitor,,,,,

.... but was methodically moving from flower to flower, collecting something .... 

.... which I imagine was nectar rather than pollen. It might have been been transporting some pollen as it walked from flower to flower in the inflorescence but ants like this are unlikely to be very effective pollinators. 

The two-segmented waist indicates that this is an ant in the genus Myrmica.

At this point I had to beat a retreat, because its fellow ants had found their way up my trouser leg.

Meadow ant metropolis

The undisturbed grassland in glades in the hawthorn scrub in Auckland Castle Park, at Bishop Auckland in Co. Durham, is home to an astonishing collection of meadow ant nests. There must be about 200 of these domed nests on the sunny south facing slope, with many more scattered throughout the park.

At the time of writing they are dormant but at the peak of activity in summer each is home to tens of thousands of ants and - like icebergs - there is more of the colony below ground than above.

There are so many that they are easily visible in satellite imagery. This is a screen grab from Google Earth. Double click on the image to enlarge it, then look for the two groups of pale dots across the centre of the image, just south of the footpath that snakes across the map.

This enormous concentration of ant nests makes it a perfect feeding site for green woodpeckers, which are ant-feeding specialists. I can't think of a single time when we've visited when I haven't seen or heard one (though I've yet to get a decent photograph!).

One curious feature of the ant metropolis is that every nest is capped in winter with a single species of moss - neat feather moss Pseudoscleropodium purum. 

When the grasses die down in winter the vibrant green moss has a chance to thrive in its place in the sun, surrounded by dead grass.

There's plenty of moisture for most of the winter months but the moss's enduring success in this habitat, which can at times be very dry in such a sunny, south facing site, may be due to the arrangement of the moss leaves.

The leaves are arranged like a spiral whorl of overlapping cupped hands around the long axis and the 'cups' hold water

You can see the effect here - when the moss is moist it has this very shiny, inflated appearance. Under the microscope you can actually see water trapped under the leaves,

Ivy - the all-year-round carbon dioxide fixer

Ivy's flowers provide a wonderful nectar and  pollen resource for insects in autumn (see some examples at the bottom of this post) and its berries are a vital food  resource for migrant birds in early spring, but it also has another important attribute with more general implications.

As an evergreen that stores carbon in its woody trunk, ivy is an all year-round carbon dioxide fixer, constantly removing the gas from the atmosphere. In that respect it contributes towards combatting the build-up of carbon dioxide in the atmosphere, which is the underlying cause of global climate change.

Deciduous trees like this ash have a short growing growing season in our seasonal climate. It comes into leaf in May and sheds its foliage in September, so for about half the year it fixes no carbon dioxide at all. But when it supports a luxuriant growth of ivy the two organisms together fix carbon dioxide 365 days a year.







































The combined efforts of an ash tree with ivy cladding are likely to be more effective at fixing atmospheric carbon dioxide than an ash tree alone.

The tangle of  thick, woody ivy stems on this sycamore are as effective a store of carbon as the tree's trunk.

Ivy can even turn a dead tree into a carbon dioxide fixing pillar of evergreen foliage, as it did with this dead oak at Egglestone in Teesdale a few years ago. Even better, in autumn this stump became a tower of flowers, humming with insects that came for the nectar and pollen. In spring it was covered in berries.

Another example, at Wolsingham in Weardale.

Sadly, there are still plenty of ivy-haters around who are convinced that ivy is a parasite (it isn't, it just uses trees for support). They'll usually also advance the argument that a top-heavy mass of ivy is likely to bring trees down in winter gales, but most trees that are felled in this way are moribund anyway and topple because they have already been weakened by root-rotting fungi, not by ivy. Logically, a good cladding of well-rooted ivy stems is more likely to anchor a shaky tree, delaying its demise. 

The fact that trees that have been killed by fungi often have a healthy covering of ivy suggests that it might well be resistant to some of the fungi that kill trees.

From all of this you might have gathered that I'm something of an ivy enthusiast - not least because of the insect fauna that its flowers attract in autumn. All of the pictures below were taken in a few minutes late last October on another ivy clad tree just across the road from the oak-clad stump pictured above.