Two New Flies for Swansea

Andrew Lucas wrote:

Much of my natural history recording in recent years has been devoted to SN6802, my home 1km square, which includes some of Clydach and a small part of the Cwm Clydach RSPB reserve. In the last week, my efforts have been rewarded with a couple of nice finds 

Phasia hemiptera is an impressive tachinid fly that I found flying around hemp agrimony in the beer garden of the New Inn pub, Clydach on 8 August 2014.  Its size, and the reddish orange hairs on the side of the thorax, distinguishes it from other species in the genus.  I caught a female, but the males are even more striking, with boldly metallic blue and white patterned wings.  In the larval stage, the insect is parasitic on shieldbugs.  The female lays her eggs on a bug, which then hatch and eat the insect from the inside out!

SEWBReC have advised that this is the first record they have received  for P. hemiptera in the City and County of Swansea, although its presence is no great surprise, as it has been found a number of times in the Llanelli area.   The species has been recorded as far north as Inverness, but most records come from southern England and the Welsh Marches. 

Rhingia rostrata is a woodland hoverfly, similar to the much more common R. campestris. It is distinguished (Stubbs & Falk 2002) by the uniformly light side to the abdomen, whilst  R. campestris has a dark line along the abdomen edge.  But it’s a much classier insect than R. campestris, with a bluish thorax and lighter abdomen that is obvious even to the naked eye.  I came across several feeding on hogweed along the footpath near the car park at Cwm Clydach RSPB reserve, again on 8 August 2014.. Rhingia hoverflies are unusual amongst the British Syrphidae, in having long mouthparts tucked away underneath the rostrum that projects from the head.  This allows them to feed on deep flowers that are inaccessible to most hoverfly species.  The larval stage of this species is a mystery, although it is thought to feed on rotting material or carrion, as R. campestris is known to use cattle dung.

SEWBReC and the NBN gateway (https://data.nbn.org.uk/) have R. rostrata only recorded once previously in Glamorgan, near Nicholaston Woods in 2009, although the hoverfly recording scheme (http://www.hoverfly.org.uk/portal.php)  has records from SS69 in 2009, and ST09 in 2001.  It has a similar distribution to P. hemiptera, with the northern edge of its distribution lying in the Lake District

References

Stubbs, A.E. & Falk, S.J. (2002) British Hoverflies.  An illustrated identification guide. BENHS.