We have to acknowledge some uncertainty about this species, which is considered to be one of 5 difficult Chrysotoxum species to identify in Great Britain (*1). To some extent we are basing our identification on the status and distribution of these 5 species. One of the other 5 is Endangered, whilst another is National Scarce. The remaining 3 species are all frequent, but cautum is the most frequent in our are. All the above reference information was taken from *1 below. This book also provides other hints based on appearance which in general help suggest our species is indeed cautumn.
Here seen perched on a creeping buttercup flower.
*1: Ball, S & Morris, R. (2015)Britain’s Hoverflies A field guide. Oxfordshire: Princeton University Press.