Saturday, 5 October 2013

Flying Ants

2nd October was “Flying Ant Day 2013” here. That was the day when the ants with wings left their nests. The day varies each year because it always follows the first  rains  that end the summer dry spell. Every summer is always dry, but they are not droughts such as are experienced for example in Australia and USA. The first rains also bring a drop in temperatures.

Weather forecasts are much more accurate than they used to be and I knew about a week in advance when the rain would begin. This is very useful information because it allows time to deal with work that absolutely must be done in advance of it happening. For me that meant removing the irrigation pump from the river as the first priority. I always leave it in position until immediately before local rain, because being an optimist, in the years when the river stops flowing I hope for sufficient of a thunderstorm somewhere in the mountains at the top of the catchment area will begin the river flowing whilst we are still dry. It did happen one year. Harvesting fruit and vegetables that are ready comes next. Figs and tomatoes are particularly prone to splitting with a sudden influx of water after they have been dry for so long. Olives are also at risk, but I had been carting out water in the tank of my boom spray to supply a little to those trees where the fruit was beginning to shrivel and I hope I have prevented damage.

There was a little rain early on the morning of 27th September with another 53mm falling during the day and a further 50mm over the next couple of days. Temperatures tend to be fairly static on a daily basis, changing little from one day to the next. It is rare to get a change of more than two degrees on consecutive days, but the rain makes one of the two exceptions in the year. Temperatures had been a degree either side of 31ºC up to the 23rd with slight falls as the clouds moved in and a drop to 21º when the rain began. It felt decidedly cool the first day, despite the fact that I consider that temperature to be very pleasant most of the time. There is a similar fairly sudden change each year in May when we begin to receive warm southerly winds and the shade temperatures increase. It is always warm in the sun, even in the depths of winter.

On the 2nd October around 10 am the ants began to take to the air. I had seen the numerous holes that appear around nests earlier in the morning and a few winged ants coming out of them. For a few hours they were on the wing, but not as numerous as in other years. Perhaps my efforts at destroying nests on the quinta is beginning to have some effect. Our biggest problem is the Seed-harvester Ant and they cause considerable economic loss so I spend some time searching out nests and killing the occupants, but many nests have only a single entrance/exit that is often covered through the summer heat and it is difficult to find them.

These ants do exactly what their common name suggests – they harvest seeds. Millions of them. I have lost all seeds sown in the garden on more than one occasion, and when I can spot the ants in the process I follow them to their nest, but a hundred feet of small seeds can disappear overnight. They also cart away many kilos of grass and clover seeds when fields are sown. They have no problems whatsoever with cereals, maize, smaller beans and even White Lupins. I have not yet seen an ant carrying a Broad (Fava) Bean. I have also lost about 20 young olive trees to ants building their nest in the rootball of newly planted and young trees and the tree dies. The Seed-harvesters are not the only culprit in these losses though, because there is a much smaller ant (no idea what it is) that likes to do the same.

In previous years there has always been an ant to approximately each square foot after they land. This year it was less than one to the square yard. They always drift downhill on this property whereas it seems they normally swarm towards higher points. Their behaviour is similar to that of the honey bee when a new Queen emerges and drones fly to mate with her in the air. Whilst the male ants still very much outnumber the females, there are many potential Queen Ants on the wing. Fortunately most of them fail to establish a nest. As with bees, the males merely die.

There is a lot of information on the internet for those interested, simply search the term “flying ants” and included, for those specifically interested in Portugal or Spain, there is a very good and easily readable paper with the title beginning “Nuptial flights of the Seed-harvester Ant (Messor Barbarus) in the Iberian Peninsula………” by Gomez and Abril of the University of Girona and published in the Myrmercological News of January 2012.