Since we last reported to this Symposium in 2011, a great deal has changed in the Hoverfly Recording Scheme's activities and in the state of British hoverflies. A big change was the establishment of a Facebook page in 2013. Prior to this, we received around 20-30,000 records per year, but few resulted from online posting. In each of the last two years we received more than 100,000 records, mostly from online postings. This has shifted the balance towards records of common and photogenic species, giving the impression that these have increased whilst the more obscure and difficult to identify have appeared to decline. This change challenges our ability to assess what is going on and has required new analytical techniques to account for evolving recorder behaviour.

These analyses suggests that around half of British species are in decline whilst less than 15% are increasing. The declines are most marked in the south-east where urbanisation and intensive agriculture are most prevalent. Some guilds are more affected than others, with wetland species being particularly hard hit. At the same time, new species continue to arrive from the Continent. We are also detecting changes in range, with some declines in the south-east being matched by expansion in the north-west and the northern boundaries of some species extending. Flight periods are also changing.

Given the ad hoc way in which our data is collected, it is difficult to assess the causes of these changes with any certainty. Habitat loss, widespread pollution and climate change are typically invoked. We can make no specific correlations, especially as the data relate to the presence of mobile adults rather than of larvae which, in many cases, will be far more niche-specific.