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Saturday, 19 May 2018

More on Pachydraba steropodes

Whilst I`m not trapping at present as I`m otherwise (very) busily occupied, today (19/5) I did manage a two-hour `jolly` around midday mostly near Llandeilo, the aim of the outing being to search for Pachydraba, an introduced Australian micro known from Aberglasney Gardens and elsewhere in the Carmarthen-Llandeilo section of the Tywi Valley.
I wanted to see if it was established in the area SE of Llandeilo town and went to Coed Penrhiwiau SN662237, a lovely hidden `cwm` NE of Ffairfach. I`ve always liked this site which is - unusually for Carmarthenshire, a wet base-rich wood. I`d moth trapped there once, leaving an actinic overnight, and I recall several clouded magpies around the trap when I returned early the next morning - the food plant, wych elm, is common. The wood is also the only known Carmarthenshire (and `Dyfed`) site for the conical snail Cochlodina laminata and the harvestman Sabacon viscayanum occurs under loose flaggy stones in damp areas. I additionally remember finding the very scarce hoverfly Criorhina asilica here and doing a bit of `air punching`
It is extremely easily accessed - you just drive down a lane, where there is good parking, and walk towards the chapel area and beyond. There is small waterfall, which given the semi-calcareous rocks, may hold some bryophytes of interest.
After parking, I went to the nearest clump of soft shield fern to look for Pachydraba but, unlike my last day out looking for this micro-moth, none were present...nor on the other two fern clumps nearby. I thought perhaps that the flight season may have been over. A few minutes later, whilst sweeping some ramsons, I noted two tiny moths and, even though I`d just been looking for Pachydraba, I assumed that they were Coleophora. However, seconds later, I saw the distinctive outstretched wings of Pachydraba. So, they also occur off the host ferns (soft shield and possibly/probably male fern). I found more individuals away from ferns by sweeping elsewhere in the wood, but not in great numbers, which suggested that we may be over the peak flight period (end of April/early May?).
This moth has been proven to breed on the sporangia of soft shield fern but, searching the undersides of the fern fronds, it was obvious that the sporangia were only in a very early, immature stage of development. I assume that eggs may have been laid but I`ll have to re-check one or more of the known Pachydraba sites later in the season to see if I can spot any silky tubes. Bear in mind too that other micros feed on sporangia - indeed, I later caught one of them - a single Psychoides filicivora.
I also found Pachydraba in Cae`r Goed/Tregyb Woods SN641219, but none were found in woodland near Derwydd Mansion.
It was a worthwhile little trip which produced two more new sites for this moth and also suggested that sweeping, rather than just fern-searching, can also be a method of finding this species.

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