Newsletter no. 8 Winter 2002/2003

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REPORTS OF RECENT FIELD TRIPS

The last newsletter reported on our trips up to 20th July 2002. On 27th July, we went to Ashwell Quarry and caught a surprising 107 species of macro and 63 micros - a total of 170 species and probably a group record! The surprise is that this minute nature reserve, an overgrown and long-disused chalk quarry, is totally isolated in the arable-desert landscape near the border with Bedfordshire and Cambridgeshire. Whilst light traps "pull in" moths as they fly through the arc of the light, the nature of the surrounding landscape suggests that there would be little ground-level movement and that as a consequence a very high proportion of the moths caught can be related directly to the disused quarry. There were lots of Least Carpet (Idaea rusticata) - interesting because it indicates that the spread of this species outward from the Thames and London has reached the north of our county. There were also lots of Dark Umber (Philereme transversata) -a species unfamiliar to many of the 22 people present. There was also a Scarce Tissue (Rheumaptera cervinalis), several Fern (Horisme tersata), Small Waved Umber (Horisme vitalbata) and other chalk habitat species. At the trap on the edge of a weedy pea-field on the quarry perimeter we were surprised to catch Chamomile Shark (Cucullia chamomillae) and Wormwood Shark (C. absinthii) together; the former is probably under-recorded but the latter is certainly scarce in Hertfordshire. The micros included the pyralid Numonia marmorea - surprisingly the first Hertfordshire record since 1933.

The visit to Lemsford Springs on 10th August was designed to see if the Butterbur moth (Hydraecia petasitis) was still present; the foodplant certainly is - in abundance. In spite of the accompanying sarcasm (which went something along the lines of "why on earth is he putting a trap on top of a hot, less than stable, pile of rotting grass cuttings in the water's edge instead of putting it where we can all see it on the path - clearly the man is mad - etc, etc"), I did indeed put a trap in an impossibly difficult place to examine and we were rewarded with two males and one female Butterbur moth. However, the unseasonally cold night produced only 53 macro species in total, in spite of the last few fools (sorry, members) remaining until 3am.

It was equally cold on the next rip - to Frithsden Beeches on 31st August (the 17th August trip was cancelled). The temperature fell to 9.1º C at "base camp" but in the wood it was at least three degrees colder. In spite of running eight lights and setting up several wine ropes, we only managed 30 macros and 15 micros - oh, and lots of hornets!!! There was nothing out of the ordinary, though a freshly emerged Rustic (Hoplodrina blanda) indicates that there was a second generation of this species in 2002.

The cold spell continued and Whippendell Wood, Watford, on 7th September can, at best, be described as a disaster, with only ten macros and 9 micros - an abysmal total comprising common species only. The saga of the coffee cups will doubtless be recounted at the indoor meeting!

Similarly low totals coincided with similarly low temperatures on 14th September at the Butterfly Conservation nature reserve at Millhoppers Pasture - over in the extreme west of the county, although we did catch a single Vestal (Rhodometra sacraria) - an immigrant species. The target species (Pale Lemon Sallow - Xanthia ocellaris), last seen in Herts in 1937, failed to show itself, in spite of us being in the best part of Britain for veteran native Black Poplar. However, a number of autumn species were recorded and some of these were new species for several members. These moths included Red-green Carpet (Chloroclysta siterata), Canary-shouldered Thorn (Ennomos alniaria), Dusky Thorn (Ennomos fuscantaria), Black Rustic (Aporophyla nigra), Sallow (Xanthia icteritia), Pink-barred Sallow (X. togata), Centre-barred Sallow (Atethmia centrago) and a Red Underwing (Catocala nupta).

We went back to Ashwell Quarry with high hopes, on 21st September. Five lights were run from just before eight o'clock until half past midnight and the air temperature surprised us all by actually rising - from 11.3º C at the start to 12.5º C at the finish! Several immigrants included Silver Y (Autographa gamma), Dark Sword-grass (Agrotis ipsillon), the Rush Veneer (Nomophila noctuella) and the Diamond-backed Moth (Plutella xylostella). A male Single-dotted Wave (Idaea dimidiata) was a surprising arrival at the sheet - it is normally single-brooded with adults in July and early August. This record surely suggests a second brood in 2003. Several autumn-flying species were also noted and the total catch was 30 species.

With some trepidation we revisited Whippendell Wood on 5th October. The catch ought to be numerically lower than on the 7th September trip? Of course, we were wrong: there were 19 macros and 13 micros. A freshly emerged Riband Wave (Idaea aversata) was surprising - second broods in September are not unknown in the south-east but this was fresh out of the nest on 5th October. Being October, we managed to catch a "November" moth - I did warn you of the unsuitability of many English names! In fact, it was a female, very well marked and almost certainly a Pale November (Epirrita christyi), but only the males of wild caught adults can be named reliably and only records based on males are permitted in the Herts Moth database.

Our final trip to Frithsden Beeches was on another cold night. Seven macros and one micro were encountered, though this time we did get lots of male "November" moths and all of these were Pale November Moth (E. christyi). Before the light trapping started we also managed to record an additional 17 species as leaf-miners.

The 19th October trip to Ashwell Quarry was cancelled. Madness, dedication or a combination of the two took us back there two weeks later, however, for the final trip of the year, on 2nd November. It was cold, as expected, and the moths were almost as scarce as hen's teeth, but then we only wanted to record the half dozen or so species that should have been there so we could put the dots on the distribution maps. Five macros speces and one micro gave us a total of six, running just four lights from half past four until eight o'clock. The catch included the first Winter Moth (Operophtera brumata) of the year - a sure sign that it was time to pack the generator away until the spring!

An extra trip, during daylight, was organised at short notice on 26th October to look at leaf-mining moths in Balls Wood and Hertford Heath. I hope that everyone received notice of this - anyone who did not should let me know so I can identify any weak links in the communication chain. We gathered at the Jolly Pinder pub in Hertford Heath village (well- it was lunchtime) and eventually made it to the woods. After a brief demonstration of what we were all looking for, the twenty or so members present set off, armed with plastic bags, to see what they could find. By the end of the afternoon, we had several bags full of leaves - and some of them even had mines in them! We managed to identify most of the species involved before we departed, though a few had to be taken away either for closer examination under a microscope or for breeding through of the adult moths (not all mines can be named just by looking at them). We ended up with 51 species and, more importantly, everyone had a fun afternoon out. Highlight of the day was a mine on a Meadowsweet leaf in Balls Wood. In fact there were lots of mined leaves, but these were almost all made by larvae of the flies Agromyza filipendulae and A. potentillae. One mine out of the twenty that I collected, however, was unmistakably that of the moth Stigmella ulmariae - a Nationally Notable species never before recorded in Hertfordshire.

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