Northants Diptera: Mid September 2017

The cool, wet weather of late has not been great for fly hunting. However, there seems to be more fungi about in the woods and this could be good for those flies that breed in the fruiting bodies of fungi. There are several families of flies that do this and some are fairly elusive as adults. Platypezidae is a family that I hardly ever come across so I will be looking out for these over the next few weeks. One way of finding them is to collect some fungus and keep it in a box with ventilation and see what emerges. Apart from flies a number of saproxylic beetles may emerge.

I briefly visited Pitsford Water, Holcot Bay yesterday to look for suitable sites for a fly identification workshop tomorrow. The workshop is one of a series that the Northants Biodivesity Records Centre is running under its WILDside Project. The project is aimed at encouraging more people to submit records of wildlife to the centre and to develop skills for the next generation of recorders.

Before I was driven off by a heavy shower I noted some flowering ivy, always a good nectar source at this time of year. Two attractive hoverflies were visiting the flowers - Myathropa florea and Volucella zonaria. The latter is our largest hoverfly and has the common name of hornet hoverfly because of its close resemblance to and association with hornets. It only arrived in Northants in the mid 2000's but is now reported quite frequently, especially from gardens growing Buddleja.

Volucella zonaria Pitsford Water 15/9/2017

Distribution of Volucella zonaria in Northants by end of 2015.

Map kindly supplied by Stuart Ball of the UK Hoverfly Recording Scheme.

Whilst at Pitsford I examined the trunks of poplars, especially those that had been felled, looking for flies associated with rotting sap. I did not find any on the trunks but sweeping adjacent foliage produced two specimens of the cranefly Gnophomyia viridipennis. The larvae of this fly live in the sap layer and especially favour poplar. The adult is distinctive as it is one of the few all black craneflies and has bright yellow halters. There were no records in modern Northants up to last year, although it had been recorded in the Peterborough area of Vice-county 32, the historical area of Northants. I found it last year at a log pile in Sulby and had found it on the Holcot Bay poplar log earlier this year. So yesterday's find was the third county record.