I first came across the Eristalinus hoverflies on the rocky shores of the Coigeach peninsula in Wester Ross a few years ago. It was a sunny day, and numerous shiny black hoverflies, which I did not recognise at the time, were dashing about basking on the rocks and occasionally settling on the Sea Pink flowers to feed. I had no net, and was totally unsuccessful at securing a specimen. I returned with a net the next week, and this time bagged a specimen. One look at the spotty eyes confirmed the genus, and a more detailed look at home with the microscope identified it as E. aeneus. The Provisional Atlas of British Hoverflies showed no records at all of this fly between Skye and the Moray coast, so it was clearly a record of interest.

In subsequent years I have found it at several places beween Morvern and Wick, so it is probably present all round the N and W coasts of Scotland (see map).

In summer 2004, on a couple of canoeing trips, I came across its very similar congener E. sepulchralis in very similar habitats at Applecross and on the Summer Isles. The Provisional Atlas showed again no records in that area, but as with many things in the N of Scotland, that might be more to do with the lack of recorders than a real absence of the flies.

Identification

The two species are fairly easily recognised as hoverflies by their characteristic hovering and darting flight. E. aeneus is especially distinctive as it is fairly large (a little smaller its relative the common Drone-fly Eristalis tenax), thick-set, and strikingly shiny. E. sepulchralis is smaller, less shiny and with a more tapering abdomen that gives it a less heavily-built look. To be certain, the eyes must be examined with a lens. Both species have diagnostic spotted eyes (for hoverflies, that is - many other flies, especially biting clegs, have spotted eyes too), but while sepulchralis has the eyes completely hairy, aeneus has hair only on the upper half.

Photo © Hans & Hania Arentsen, www.gardensafari.net

All the other closely-related species of hoverfly breed in sites low in oxygen, and have 'rat-tailed maggots' with long breathing tubes which act as snorkels. Eristalinus breeds in rotting vegetation, and aeneus has long been known to associated with the coast and with rotting seaweed in particular. E. sepulchralis is (at least in England) much more of an inland species, but the Highland records may suggest a different ecology up here.

Records

Any records can be reported initially by email giving date, place, six-figure grid reference and any other relevant details. Directions for sending specimens (which will normally be required for confirmation) will then be provided.