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 |
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.
ReplyDelete