October 2019

I found a new fly last month.  It was sitting on a wild carrot flower and there was something striking about it that made me get the camera and take some photographs. 

Ectophasia crassipennis

When I opened up the Facebook group to try and identify the fly, there was a picture of an identical fly with the comment ‘This is the 8^th or 9^th record we’ve had this year – mostly from Devon and Cornwall and one from Sussex.  It is new to the UK this year.’  So my fly was only the 9^th or 10^th record for the UK and the second for Sussex.  The fly goes by the name of Ectophasia crassipennis.  It doesn’t have a common name.  Its traditional range has been in southern Europe and the warmer parts of central Europe but it now appears to be expanding its range, or moving its range farther north due to the acceleration of global warming (which is now often called global heating to emphasize just how serious it is).

The fly Ectophasia crassipennis, is a tachinid fly.  This is a large group of flies (about 270 species in the UK) that parasitize other species.  They are parasitoids, rather than parasites – the difference being that parasitoids kill or fatally weaken their hosts whereas parasites take resources from their hosts but don’t kill them (like the stylops I described in a previous Nature Notes).  Some tachinids parasitize butterfly or moth caterpillars, but this species parasitizes hemiptera, for example, shield bugs.  They lay their eggs on the back of the insect where they can’t be reached and when the larvae hatch they burrow into the insect and eat it from the inside.

Tachina grossa

Incidentally, on a recent trip to Braunton Burrows in Devon to survey bumblebees we found another tachinid fly – Tachina grossa – it is the biggest and ugliest fly I have ever seen, as big as a bumblebee and being black and hairy, also resembles one.  That particular fly lays eggs on hairy caterpillars like the oak eggar moth with eventually fatal consequences for the moth.

I seem to have seen more hornets in the garden recently.  Normally we get the occasional one preying on the wasps eating windfall apples, but recently I have regularly seen one hunting round our meadow area.  A week or two back we put out the moth trap to see what late summer species were about.  Imagine my surprise when I looked in the trap the following morning and found more than a dozen hornets in there.  This made emptying the trap a much more hazardous task than usual.  They were all a bit dopey and most flew off as I pulled the egg boxes out.  A couple of them ran out of energy and subsequently died, but judging by the moth wings in the bottom of the trap, none of them had gone hungry during the night.  Seeing so many hornets, as well as the hornet rove beetle I described in last month’s column, suggests that there was a colony nearby, possibly in the wooded area at the bottom of Elm Lane as that is the direction I have seen them fly off in.

European Hornet - Vespa crabro