From anecdote to evidence: the flying ant survey

Citizen science has rapidly increased in popularity, but for decades volunteers have contributed to ecology through species recording schemes. Today, projects vary from counting butterflies in your garden to cataloguing the shape of galaxies. The Society of Biology launched their first citizen science project last year with the University of Gloucestershire: the flying ant survey.

Each summer huge numbers of flying ants suddenly appear around the UK, and many people have anecdotes about their ‘flying ant day’ experiences. The flying ant survey is a chance to turn anecdotes into data.

This amazing phenomenon happens when young queens leave the nest to create their own colony. The survey was an ideal way to learn more about this behaviour: how synchronised is it around the UK? Do particular weather conditions trigger their emergence?

The flying ants normally encountered in towns and gardens are the black garden ant Lasius niger. Black garden ant nests have a single queen and typically around 5,000 workers, although there can be as many as 15,000. The wingless ants seen throughout most of the year are workers, collecting food for the colony. Workers are all female and will be alive as adults for about a month.

Ants mate during flight, so males and new queens both have wings. Looking at a swarm of flying ants it is easy to distinguish between males and queens because the males are much smaller. Queens need to be larger as they can lose half their body weight whilst rearing their first brood. The queen is not in charge of the workers: her job is to lay eggs to create more workers, as well as new queens and males.

[caption id="attachment_35851" align="alignright" width="200" caption="Black Garden Ants Credit Philip Gould"][/caption]

The males generally only live for a day or two after the mating flights. Males are only produced during ‘flying ant season’ and don’t do any work in the nest; their only job is to mate with new queens. The ratio of males to queens seems to vary considerably between nests.

During their ‘nuptial flight’, new queens leave to mate and found a colony of their own. Once the males and immature queens have mated the queens will discard their wings as they are no longer necessary.

Black garden ants nest underground, and the first thing the queen does is to dig herself an underground chamber. The ant lifecycle is very similar to that of a butterfly: the egg hatches into a larva which feeds up then pupates and emerges as an adult ant. The queen won’t eat any food until the first adult worker ants emerge and leave the nest to collect food.

Professor Adam Hart from the University of Gloucestershire is analysing the flying ant survey data. He said: “Each year males and virgin queens take part in remarkable mating flights. So-called ‘flying ant day’ is one of the rituals of our summer, and in 2012 we turned anecdotal evidence into a scientific study.”

The 2012 flying ant survey received over 6,000 reports of flying ants and unexpectedly revealed two flying ant days.

Professor Hart says: “We found a relationship between flying ant swarms and weather conditions, which we expected, and geographical variation, which we didn’t expect.”

[caption id="attachment_35852" align="alignleft" width="200" caption="Credit Matthias Becher"][/caption]

Approximately 1 in 5 sightings happened on Tuesday 24^th July, and another 1 in 5 came two weeks later on Wednesday 8^th August. These peaks were extremely striking, but still these two flying ant days accounted for fewer than half of the records. In fact, flying ants were a common sight for the days in July and August around the two peaks.

The time between the two peaks was a period of low pressure, which is usually associated with clouds, wind and rain. This suggests that the weather had a large role to play in determining when the ants flew.

What we don’t yet know is whether these two peaks happened because the first peak was interrupted by bad weather, or whether this is a common pattern. The survey will continue over the next few years to explore this question further.

Interestingly, there was no evidence of a trend across the UK, with no difference in timing between the north and south. The geographical pattern was in fact very complex, and it is likely that local conditions played an important role. Even over a small area, emergences happened on different days, suggesting that local synchronisation is not as precise as is widely believed.

One factor which was very consistent was the time at which the ants emerged: normally between 16:00 and 18:00. This suggests that, although weather affects whether ants swarm that day, it doesn’t affect the time of day they fly. Professor Hart says: “Mid-afternoon flights make sense: this gives them just enough time to find somewhere to hide, but not too much time for exposure to predators. They can’t risk flying at night because they can’t see and it’s too cold, so the afternoon is a good way to hedge bets.”

Flying ants always appear in late July or early August in the UK, but initial analysis of 2013 data shows a protracted period of flying ant activity. Reports were already coming in during the third week of July and they continued well into August.

The 2012 survey produced very valuable data, but it is important to run the survey for multiple years to help understand how and why the timing of emergence changes.

[caption id="attachment_35853" align="alignright" width="200" caption="Queen abandons her wings"][/caption]

Christina Catlin-Groves, a PhD student at the University of Gloucestershire, says: “Last year’s findings are just the tip of the iceberg. We just have one year’s worth of data and with the unusual summer of 2012 we really need more years to let us build up the bigger picture. It will be exciting to see what this year brings so please keep an eye out for flying ants and fill in our survey online.”

Missing flying ants? Why not spot a spider? Following the success of the flying ant survey the Society of Biology has launched a new recording scheme to monitor house spiders.

There are about 650 different species of spider in the UK, and most of them will never come inside. Each autumn, however, male house spiders come indoors in search of a mate.

Dr Rebecca Nesbit from the Society of Biology says: "We are recording the large, hairy Tegenaria spiders, which are most often called 'house spiders'. The number seen in houses increases in the autumn, and we want to know the timing. Is it the same time everywhere in the UK? Is it the same time each year? Is it related to weather conditions?" By recording sightings of house spiders, it is possible to investigate the timing of this year's mating.

The app 'Spider in da House' has been developed by the Society and built by TouchApp. It allows people to report their sightings of Tegenaria spiders and helps identify other spider species.

Spider in da House is available in the Android and Apple app stores and records can be submitted online www.societyofbiology.org/spider.

Ant Facts

Scientific name: Lasius niger

Distribution: One of the most common ant species found in Europe and is also some parts of North America and Asia.

Habitat: They are mainly found in gardens under bricks and stone and also in pavement cracks. L. niger will often enter houses.

Diet: Some colonies of black garden ants will farm aphids for the sugary honeydew they excrete. They are also predators and scavengers, and will eat insects, spiders and other small invertebrates. Nectar from flowers is another common food source.

Predators:They provide a vital food resource for many species of birds, particularly swifts and gulls.

The Author Karen Patel is the Communications Assistant at the Society of Biology.

Contact www.societyofbiology.org