Sunday, 3 August 2014

Is something happening with Rhingia campestris this year?

Rhingia campestris is a common, readily identifiable species that is reported by specialists and generalists alike. It attracts a fair amount of attention from photographers and figures within the 20 hoverfly species most frequently recorded by photographers. It is also known to be very responsive to the effects of drought – a feature that Stuart and I drew attention to in a presentation to one of the hoverfly symposia several years ago. This relationship had previously been highlighted (but not recognised) by reports of its abundance dating back to 1947. In really hot years, the second generation is largely absent. This can be seen from past records, but sadly we generally get insufficient records to do a great deal with the data.

In 2014 R. campestris was frequently reported in April and May, and it is clear from the data that this is one of a suite of species that definitely respond to warm springs. What has happened since is more puzzling. The numbers of records have tailed off but have not dropped to a clear separation between generations. Perhaps this is the effect of northern generations emerging a little later? I must look at the data in more detail to see if this is the case, but what is clear is that the overall shape of the graph for the year to date (using a five week running mean) is somewhat different to the previous three years for which sufficient photograpic records exist.

What is also very clear is that 2013, where there was a very hard winter and later spring exhibited a clear twin-peaked phenology that is less evident in other years. The data may not be robust enough to make too much of this observation, but I do wonder if a study of bivoltine species might show how such species change their emergence patterns in response to longer breeding opportunities.

This brief observation illustrates how it may be possible to generate useful and relevant information on the effects of changing climates on our wildlife. It shows that 'common' species are highly relevant to the understanding of the natural world and should encourage more recording of such species. The big question is 'how to deal with the volume of data that could be generated by a serious initiative to record common insects?' Maybe there is scope to develop ideas by MSc students?
Yearly phenology for Rhingia campestris using photographic data using a five week running mean

1 comment:

  1. I was thinking about this the other day. Usually, when the bindweed comes into flower along the canal this time of the year I see an explosion in R. campestris numbers with each flower usually having one feeding in it. This summer, I see one and think well of it simply for being a new one for the day's records.