Wednesday, 13 July 2016

Bright Horsefly (Hybomitra distinguenda) at Blaencaerau

The family of Hybomitra horseflies are hard to discern from photographs, so multiple angles are needed to get all distinguishing features. Luckily the two similar species have not been recorded in Wales but you still need to prove it is "Hybomitra distinguenda". The serious of photos below does just that.

 Tergites on the abdomen T 1 to T4 are coloured orange on the sides, with a black tapering stripe in the middle running down the body. No other member of the family has this.
 Larger [Tabanus] horseflies have only one stripe on eye, so this is certain to be "Hybomitra". The eyes are also covered in fine hair, where as the Tabanus [larger] group has hairless eyes. Grey based antennae rule out the rarities which have orange based antennae. The second segment is also orange based. The combination of these two antennae features rule out the commoner "Hybomitra" as well.
 This is a medium sized male [eyes touching] Horsefly. I posted a Tabanus a few days ago from the same area and the size difference is obvious.
Finally the legs are neither all black, nor is the middle tibia very hairy, which again rules out other similar species. So this is a Bright Horsefly [Hybomitra distinguenda]. Paul Tabor also recorded one near Parc Slip, Aberbaiden last week, But as far as I know this is the first for the valley.

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