Saturday, July 7, 2012

UK's flying ant swarms counted

Scientists are attempting to count the number of places flying ants appear in the UK, as they swarm across the country during mating flights.

"By running the flying ant survey we can learn more about the ecology and behaviour of ants," said Dr Mark Downs, of the Society of Biology.

The charity aims to shed new light on the reasons they appear all over the country at the same time.

The results will be announced during National Biology Week in October.

The seasonal appearance of flying ants occurs when they embark on their "nuptial" or "mating" flight, in the first step to founding a new colony.

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The appearance of flying ants above ground follows the growth of the colony underground, thanks to the efforts of the female workers over the summer.

"Eventually it gets to the point where it's kind of big enough and strong enough that it can start producing... potential new queens, which are a bit bigger, and the males," said Dr Adam Hart, an ecologist and insect expert at the University of Gloucestershire, who is working with the Society of Biology on the survey.

The males and potential queens are the winged ants seen during the summer months.

The virgin queens mate with males during the flight, after which the females lose their wings and attempt to found a new colony.

It will be the only time the queen mates and the males will die shortly afterwards, though their sperm will last the queen a lifetime of egg-laying.

It is important that the flights are synchronised between nests, says Dr Downs, the Society of Biology's chief executive.

"The flying ants won't survive very long and need to maximise the chances of meeting ants from other colonies to mate with. But how do they do it?

"Do flying ants appear at a very similar time each year, determined by the ants' biology, or is there a lot of flexibility in response to external conditions such as weather?"

The details about how the ants know when to fly remain a mystery, but the survey may help to make sense of it by charting the appearance of the ants through July and August.

"What we don't seem to know is the pattern across the whole country," said Dr Hart.

Flying ant-spotters are being asked to submit their sightings throughout July and August on the Society of Biology's website.

Most of the information the team hopes to collect relates to the black garden ant, Lasius niger, although the nuptial flight is a common behaviour to many ants.

Earlier in the year, biologists from the University of Girona published a study based on data from 123 nuptial flights of the seed-harvester ant, which may hold clues to the flights of UK species.

The data was gathered over a six-year period in September and October on the Iberian peninsula and the scientists were able to identify eight clusters of nuptial flight that appeared to be triggered by the same weather fronts.

The study found that the days with the highest number of flights consistently occurred a couple of days or so after rain had stopped and was clear of the peninsula.

Continue reading the main story

?Start Quote

It's hard to find any organism that lives in the same territory as an ant colony that doesn't interact with those ants?

End Quote Dr Frank van Veen Ecosystems expert

"They (black garden ants) are not the strongest fliers and they mate on the wing, so their chances of mating and finding a suitable place to nest are greatly reduced if they come out in pouring rain," said Dr Downs.

"Rain prior to the flight means that the ground is soft, which makes it easier for the mated queens to dig a nest. The flying ants probably wait inside the nest for a suitable day to fly."

The Society of Biology hopes to make the flying ants survey an annual event.

"It will be extremely interesting to try to understand how the pattern changes year on year and what causes this," said Dr Downs.

"We will be looking to see how the weather affects timings, both the weather on the day the ants emerge and the weather in the run-up to their emergence."

Amazing ants

The black garden ant Lasius niger may be small but research suggests it has a big effect on the surrounding ecosystem.

It does this not only in straightforward ways such as nest-building, which brings air and nutrients into the soil, but also in some hidden ways.

"It's hard to find any organism that lives in the same territory as an ant colony that doesn't interact with those ants," said Dr Frank van Veen from Exeter University's Centre for Ecology and Conservation.

"Usually those ants have a really big effect on those other species."

Ants often evolve in a mutualism with sap-feeding insects, particularly aphids.

The ants harvest the aphids' secreted sugar, known as honeydew, and in return the aphids are protected from predators and competitors.

Dr van Veen described how a study had discovered just how effective the protection of the black garden ant could be.

"If you put an aphid colony out in a field without any protection there is a very short survival time.

"If you put one out with fine mesh cage around it, that means that most predators can't get at it, they have much longer survival."

The experiment showed that if aphids were left exposed, but provided with an ant colony, the ants were as good as the netting at protecting the aphids, he said.

Last year, Dr van Veen completed a study that tested the "ecosystem engineering" of ants by changing the number and density of two ant species in a small area. One of the species was Lasius niger.

"We experimentally put ant nests in a plot of one square metre, either a single ant nest or two ant nests or no ant nests and we measured the densities of the invertebrates that were important for the soil," he explained.

In spite of the effect of predation at higher densities, the presence of ants had a positive effect on the density and diversity of many other species.

Decomposers, herbivorous insects and spiders, all benefited strongly from the presence of ants.

But ants still harboured plenty of secrets, he said.

Perhaps now the flying ants survey means it is the UK public's turn to add to our understanding of these complicated creatures.

Source: http://www.bbc.co.uk/nature/18674341

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