Moths on West Wickham Common in 2012

by Bill Welch.

West Wickham Common is one of a group of commons on the southern borders of Greater London which belong to the Corporation of London. It's a small common within walking distance of my house, and is mostly mixed woodland with a small area of grass and heath. I had volunteered to do the 2012 butterfly transects there, so I had a connection to the rangers.

Early in 2012 I persuaded them that it would be a good idea to run some moth trapping exercises there. There is already regular moth trapping on Farthing Downs, another City of London site, and there was spare equipment which could be brought to West Wickham. The local ranger, Luke Barley, lives in a house on the common, so power could be provided. This looked good! I was keen to do the trapping, having learned from Gill Peachey at Farthing Downs. Gill also helped to sort out the trap from an untidy store, and the City of London people were happy to have me as a volunteer.

So we started in May 2012, with the aim of running the trap overnight for one night each month, then unpicking the results early in the morning before Luke had to leave for work. Here's how it worked out.

May 2012

I set the trap on the 16th and in the morning there were a total of three moths in the trap; two micros and a Noctuid that I later identified as a Shears, Hada plebeja.

The distinctive feature of the Shears is a whitish marking on each wing that is supposed to resemble the tool it is named for, though to me it looks more like the head of a duck. But it's hard to see close up! You have to pull back and look at the moth as a whole. We also found a Brimstone Moth, Opisthograptis luteolata, in the grass near the trap. These macros were nice specimens. One of the micros was a Brown House Moth, Hofmannophila pseudospretella, and the other was a Eudonia angustea.

I tried to look professional as I unpicked the trap and recorded these meagre results. I wanted Luke to think that his help was worthwhile. But I thought it was rather disappointing.

June 2012

On the morning of June 20th, as I approached the trap I saw that the wall of Luke's house was peppered with resting moths! This was more like it. As I photographed them I saw that there were some lovely specimens. Nothing rare, but plenty that are a pleasure to find.

On the wall were mostly Geometers, including a Blotched Emerald, Comibaena bajularia; a Barred Yellow, Cidaria fulvata; and two Pine Carpets, Thera firmata. Then round the corner, low on the wall, a Notodontid: a Lobster Moth, Stauropus fagi, a lovely big furry creature. I was already pleased.

Then I undid the trap, and was very pleased. Sitting there were two Elephant Hawk Moths, Deilephila elpenor, and a Pine Hawk Moth, Hyloicus pinastri. As I went on I found a few of the likely Noctuids, including another Shears, and a nice selection of micros, mostly Tortricidae. There was also a White Ermine, Spilosoma lubricipeda, one of the Arctiidae, which promptly played dead, and when I moved it to the measuring paper for its closeup it exuded a yellow drop of something nasty. Noctuids are much less unfriendly!

There were 54 moths in total, of 32 species. A nice colourful group.

July 2012

By now, Luke knew enough to set the trap himself and I just came round in the morning. This feels lazy, but it works.

The July haul was much less colourful, but still included a couple of nice species. The most spectacular was a Poplar Hawk Moth, Laothoe populi, which almost covered my palm. But there was a bit of wind that morning, which made it harder to photograph the moths, and the Hawkmoth was whipped away almost before Luke could see it.

It's always worth searching the grass around the trap, and this time there was a nice Buff-tip, Phalera bucephala, disguised as a little twig of Silver Birch, and a Peach Blossom, Thyatira batis, giving us representatives of two less common families: Notodontidae (like the Lobster Moth) and Thyatiridae.

There were a selection of Noctuids, including a Flame, Axylia putris, and a Small Angle Shades, Euplexia lucipara. Also, a first appearance from a couple of the Yellow Underwing group. But I was surprised to see that unlike in June, there was only one Tortrix.

Altogether, there were 41 moths of 23 different species.

August 2012

This time, Isphi Blatchley came along as well. As we approached the trap, we saw that the wiring that supported the light's protector was covered with moths.

These turned out to be Phycita roborella, a Pyralid whose larvae feed on oak. I counted 28 of them on, in and around the trap. There are oaks on three sides of the house, so this made sense, though I was surprised that over the year I didn't see many Green Oak Tortrix, Tortrix viridana, a very common oak species. In other trapping events near oaks they had been quite abundant, but here there were 6 in June and that was it.

There were some pretty moths in this selection, including my favourite of the whole year, a Canary-shouldered Thorn, Ennomos alniaria. On the wall this time were some Footman moths (Footmen?): five Scarce, Eilema complana, and one Dingy, Eilema griseola.

There were two Black Arches, Lymantria monacha, one of each gender, a strikingly marked moth with noticeable sexual dimorphism. The male is smaller and has big pectinate antennae, very different from the female's antennae which are only slightly comb-like. These are what the male uses to pick up minute traces of the female's pheromones.

Two nice finds were an Iron Prominent, Notodonta dromedarius, and a Lesser Swallow Prominent, Peosia gnoma; both Notodontids.

In the grass we found a rather worn Oak Hook-tip, Watsonalla binaria, giving us another family, the Drepanidae.

There were some colourful micros, some quite pretty, such as the iridescent Roeslerstammia erxlebella. This time there were several Tortrixes, including a Eudemis profundana, looking quite exotic with its starry eyes and neck ruff of upstanding scales.

As in July, there were a handful of grass moths from the sub-family Crambinae, reflecting the presence of grass nearby. There is grass nearly everywhere, so you can probably always expect a few of these in summer.

Total: 39 moths of 17 species.

September 2012

Ishpi Blatchley and Keith Palmer joined me for a disappointing day. It was a dewy morning, during which we found a total of 13 moths of 8 species, three of them in the grass and covered with dewdrops.

Silver Y, Autographa gamma; Light Emerald, Campaea margaritata; Pale Mottled Willow, Paradrina clavipalpis; Large and Lesser Yellow Underwings, Noctua pronuba and Noctua comes; some Tortrixes and a Carcina quercana. It was generally cold and wet.

October 2012

A few autumn moths, but only 6 specimens of 5 species. It was nice to see a Black Rustic, Aporophyla nigra. Two Red-green Carpets, Chloroclysta siterata, were more or less expected at this time of year.

A Chestnut, Conistra vaccinii, and a Beaded Chestnut, Agrochola lychnis, were also seasonal. The sixth specimen was a Common Marbled Carpet, Chloroclysta truncata, from its second generation of the year.

Autumn and winter moths are generally of a darker tone than the summer ones.

Year's End

That was the last trapping session I was able to arrange in 2012. The criteria for trapping were threefold; a) Luke had to be available, which includes it having to be in between two work days. b) A few degrees above freezing point. c) Not actually raining. Even though you can catch moths in the rain, they can get soaked in the bottom of the trap, and while the minimal shelter the Robinson design gives to the bulb is OK for showers, it is not reliable in heavy rain or wind. It is now March 2013 and I still haven't been able to fix another session.

So, what could we learn from 2012? First, the overall figures. Trapping over six nights, we saw 229 moths of 89 species. None of them were rare or threatened species. (The "Scarce Footman" is actually quite common.)

There were often only one or two of any particular species. In fact, of the 89 species found on West Wickham Common, 55 were represented by a single specimen. Catching these must have been pure luck! I wonder what other species we missed?

In my garden trap a mile away, a much feebler Skinner trap, but deployed much more often, I had seen 109 species, not always the same ones.

So these results must only be a partial picture. More frequent trapping at the common, especially at the peak of the season in from June to August, would probably produce more species and give a more complete result. And we might also see more off-season species if it becomes possible to deploy the trap in winter.

Second, there were very poor results early and late in the year. The start of the year was dry, and later on it became the wettest year on record in England, so conditions were not very good for the larvae. But we will need to await several years of data to come to any sort of reasonable conclusions about this.

What about the actual species we found? I checked the food plants of the larvae of all the moths caught. Overall, they were very varied, including trees, shrubs, herbaceous plants, grasses, lichens and mosses, which makes sense considering the varied neighbourhood. We were trapping at the edge of a mixed wood with lots of oak, quite close to gardens, and with areas of both grassland and heath not far away.

Scots pines scattered around the common probably accounted for the Pine Hawk Moth, Pine Carpets and a couple of other species. In fact the variety of moths suggests a good botanical biodiversity in the neighbourhood.

And what of the trap itself? It was a Robinson trap, with a bright mercury vapour bulb. This is a reliable design that pulls in the moths, and although I have seen a custom design that might be better, there is really no problem with a Robinson. But not all moth species come to light, so it won't collect everything.

A useful point to note is that placing the trap next to a light-coloured wall and next to grass gave incoming moths extra, and differing, environments on which to settle, and I am sure this improved the catch.

If anyone wants more details of the catches, there is a spreadsheet with the full results here: West Wickham Moths 2012

A final note: there was no sign of the Oak Processionary Moth, Thaumetopoea processionea, a notifiable pest that had been seen the same year to be very well established in the grounds of the Bethlem Royal Hospital only two miles away. This is good news!

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The cross-hatched background to some of my photos is measuring paper in neutral grey with squares 5mm across, which gives both the actual and relative size of the moths.