Nature Notes #36 (Generals & Centurions)
As I mentioned in the last Nature Notes, the Hogweed near the old log at Frodsham Marsh on the warm late morning of June 29th was alive with insects, mostly flies. Each umbel had between ten and thirty flies feeding on the nectar. Most were unrecognisable to me but there were obvious hoverflies and ichneumon wasps.
The Hogweed nearest the old log had some bright green flies on them that resembled hoverflies, but there seemed to be two colour forms. Both had bright metallic green thorax, but one type had a metallic sea-blue abdomen and the other a metallic bronzed-orange abdomen. They moved around quickly and I couldn’t get really good photos but the two below show how attractive they were.
After some research, they were soldier flies, specifically Chloromiya formosa, the Broad Centurion or Green Soldier Fly, a very common species that breeds in all kinds of rotting vegetation including compost heaps in gardens. The adults feed on nectar and in particular on umbellifers. The males have the bronzed-orange abdomens and the females the sea-blue abdomens. Very attractive little flies.
Broad Centurion (male) Chloromiya formosa (green and bronzed-orange)
Then, as I walked slowly along the track below the old log towards the Weaver, I found myself stopping at every Hogweed. It’s amazing what you see when you stand still and look, as it is for birds. There were insects everywhere. Suddenly I noticed a large bee-like fly feeding ponderously on one large umbel. It was quite disconcerting being so close to it and not knowing if it was aggressive or not. But it was fine and carried on feeding and just ignored me. I took a series of photos and in the evening identified it as another soldier fly, albeit a very big one. Chinery (in litt) only has two possibilities, Stratiomys chameleon and S.potamida and didn’t indicate what their ranges were or how common they were. So I put the pictures on a forum and was surprised at the identification. It was actually Stratiomys singularior, the Flecked General, an uncommon species and only the fifth Cheshire record. They like marshy, sometimes brackish areas and their aquatic larvae are carnivorous. So, two soldiers on the Hogweed, a good result indeed.
Written and images by Tony Broome