Wednesday, 15 August 2012
Spotty Eyed Hoverfly
Occasionally, I wonder if this blog can be long lasting, given the subject is my garden invertebrates. Can I regularly find something worth writing about without repeating myself? These doubts, however, are always short-lived, as I am time and time again surprised by a new species or by regular ones behaving in ways I haven't observed before. This afternoon, before the skies opened and rain started falling after a couple of dry weeks, I watched hoverflies, always plentiful this time of year. The flowering fennel and yarrow, both with flat umbels and many small flowers with easy to reach nectar were buzzing with them. A small, stout hoverfly fed on the fennel. I didn't recognise it and I was amazed by its unusual spotted eyes. Taking photos was tricky, as the slender fennel stems swayed on the wind. I took many, and discarded most, but these are the best I managed.
The wonderful Garden Safari website helped to identify the species as Eristalinus sepulchralis. Unfortunately, despite having browsed Stubbs and Falk, the plate in which it is pictured is at the same scale than other much larger droneflies, and the characteristic eyes were not apparent in the small drawing. Also, as the drawings are based on pinned specimens, and eye colour fades on dead specimens the contrast between the yellow background and the darker spots is lost. This species is characterised not only by its unusual eyes, but also for the striped thorax, metallic bronze sides of the abdomen. Despite it being my first sighting, this is a common and widespread species, with maggots of the rat-tailed type that develop in wet areas. Adults overwinter and feed on a range of flowers.