Hoverfly - Yellow-barred Peat (Sericomyia silentis)

Yellow-barred Peat hoverfly (Sericomyia silentis) Size: 9.5-14mm Flight: May-Nov.

Species of the week – 29^th September

This hoverfly was the star species w/c 15th September and for good reason. It was not only a new species for the year but according to my records a new one ever. What was strange was that it was observed and identified in a Sheffield garden, not in the uplands where this would be typically found. As its name implies it is one of those hoverflies associated with uplands, as its long-tailed larvae are often found in peaty pools or wet rotting wood, feeding on the detritus soup.
 
So why was it discovered in a Sheffield garden when it favours acid wetlands and heathlands?

This hoverfly, as the pictures above hopefully show, is a wasp mimic with its wedge shaped yellow and black markings on the abdomen. The thorax and scutellum are black, sometimes with a tinge of red in the centre, but this was not obvious in this specimen. The edges of the wing are tinged brown, the stigma also being a transparent brown. Legs are orange-brown ending in black tarsi. Similar species are the White-barred Peat (Sericomyia lappona) which does have a red scutellum, but abdominal markings a more white-yellow.
 
It has been documented that this species can emit a loud buzzing sound which scares bees away from flowers, but I did not observe this behaviour that day so can’t confirm this. I would imagine it can produce a loud, high-pitched hum to mimic a wasp however and thus gain protection which is a more likely tactic.
 
These hoverflies have long wings and are known to be particularly strong flyers and prefer purple flowers where adults can feed on nectar and pollen. I spotted this hoverfly feeding on Red Valerian, I guess in terms of colour it’s not too dissimilar to moorland heather. The heather lands are not far away in this part of Sheffield, this garden being quite high on one of its seven hills, so maybe on this occasion one was just flying through. The other possibility, as it was a female and with such the dry conditions this year, maybe the heather had already finished flowering. Whatever the reason I am glad it dropped in.

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