Friday, 13 February 2015

The swarm solved

The internet is wonderful.  Within a matter of hours after me first sighting a swarm of insects on 13 January it had emerged that a similar swarm had been sighted at Wamboin.  The information was shifted around locally.  Then another swarm was found at Urila and discussion involved people in Sydney and the UK as well as more locally located folk.

On 13 February Roger Farrow came over to our place to try to get some specimens from our swarm which were still active a month after first being noticed,  This photo shows - as brown flecks on the pine needles - the flies settling before or after being in the swarm.
 Here is part of one (of two) swarms.
We have done some rough estimates (based on the dimensions of the swarm and a possible density of insects within it) of the numbers of flies in the swarm and have concluded that a big swarm like this might hold 60 million insects.

The trees they were using as markers for forming the swarm were pretty tall - much more than the ones at Urila where Roger had been able to get specimens from the trees using a basic net on a 1m metre long handle.  Even when the edge of the swarm at Carwoola dropped these were still a few metres up, so I got the extendable handle from a lopper and with a little help from some insulating tape we had a much more suitable weapon.

After a few swipes with this Roger had got some more specimens which he was confident, from visual examination, were the same species as at Urila.  Having seen these specimens I realised I'd been looking for insects the size of hoverflies, rather than (what is called in Canada) no-see-ums which is what these were.

This image shows the locations of Wamboin, Carwoola (ie Home) and Urila relative to Queanbeyan.

It is 32km in a straight line between the marked locations of Wamboin and Urila, which probably are not the precise locations of the swarms, but does give an indication of the minimum size of the area in which the swarms are active this year.

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