Dune Robberflies

12th July 2014 - Merthyr Mawr, Glamorgan

A weekend visit South Wales meant a few hours available to spend searching the dunes at Merthyr Mawr for some charismatic microfauna. I was hoping for Dune Tiger Beetle Cicindela maritima but drew a blank, fortunately Dune Robberflies Philonicus albiceps were everywhere I looked and provided a nice exercise for my rusty macro technique.

All photos taken with 180mm macro lens, f/8 at 1/160 -1/500 sec hand held. Species checked using the keys Stubbs and Drake (2001). 

Philonicus albiceps 12/7/2014 Merthyr Mawr

  P.albiceps is found on sand dunes all round the coasts of England and Wales, it is often common and can be abundant. Adults are found from mid May until mid October with numbers peaking in June and July (Stubbs and Drake, 2001). The larger robberflies (family Asilidae) are usually fairly obvious as such, with eyes separated by a 'dip' ('vertex' to be technical), bristly moustache and stout stabbing mouth-parts. They're all active hunters of insects and this one specialises in catching other flies as shown by this female below (prey species unknown).

Philonicus albiceps 12/7/2014 Merthyr Mawr

 P.albiceps is more than capable of tackling larger flies such this Empid (probably Empis tesselata) below.

Philonicus albiceps 12/7/2014 Merthyr Mawr

 The bigger the prey, the bigger the meal; I found a male (the shape of the tip of the abdomen is the clue in this family) sat on a rusty oil drum sucking the juices out of this Muscid (a Coenosia sp.?).

Philonicus albiceps 12/7/2014 Merthyr Mawr

 The proboscis is clearly visible piercing the prey's thorax; and while the mouth-parts are strong enough to hold the prey without using the legs, It helps that robberflies inject a venom that seems to kill their prey immediately.

Philonicus albiceps 12/7/2014 Merthyr Mawr

Reference

Stubbs, A.; Drake, M. (2001) British Soldierflies and their allies. BENHS