Westcott, Bucks - the year 2016 in review

Butterflies

It was another poor year for butterflies in the garden at Westcott.  Only 19 species were recorded from the all-time list of 30 and one particularly surprising absentee was Ringlet Aphantopus hyperantus even though it seemed to do quite well in the local area.  Perhaps it did appear but when my back was turned.  ‘Empty buddleias’ sums up much of the summer and it wasn’t until the second half of August that any of the vanessids started to appear in numbers.  Peacock Aglais io never really got going at all before heading off into hibernation and the maximum seen at any one time was six, whereas counts of 40 or 50 are not uncommon here in a normal year.  Small Tortoiseshell Aglais urticae did moderately well, building to a maximum of 33 on 30th August, but it was left to Red Admiral Vanessa atalanta to hold the fort later in the season once the ivy had come into bloom, that species achieving a maximum of 21 on 24th September.  Comma Polygonia c-album was active from mid-July until mid-October but only ever appears here in ones and twos and it was no different this year.  The migrant Painted Lady Vanessa cardui was reasonably regular from the beginning of August (three were seen together on buddleia on the 3rd) and was noted on-and-off until the final sighting on ivy on 2nd October.

Another absentee in 2016 was Small Skipper Thymelicus sylvestris, although both Essex Skipper Thymelicus lineola and Large Skipper Ochlodes sylvanus did put in their usual handful of appearances during July.

 

Essex Skipper, Westcott 23rd July

 

Once again the elms at the bottom of our garden produced half a dozen of sightings of White-letter Hairstreak Satyrium w-album during the second half of July.  However, another of the trees succumbed to Dutch Elm Disease in 2016 and we are now left with only two on which the butterfly might still breed although regrowth from earlier losses is coming along nicely.  Unusually, on 23rd July I managed to get a half-decent photograph of one slightly battered individual which left the tree-tops to visit some bramble blossom.

 

White-letter Hairstreak, Westcott 23rd July

 

The only noticeable butterfly success story in 2016 was that of Holly Blue Celastrina argiolus, with activity from up to four individuals at a time noted on 51 days between 3rd May and 4th September.  In past years I’ve seen females egg-laying on our large Cherry Laurel and that is certainly the most favoured plant here on which to see basking adults, but we do also have plenty of its regular food-plants in the garden too (holly and ivy).

Holly Blue, Westcott 14th May

Moths

Trapping effort in the garden was almost identical to that of 2015 with the twin-30wt actinic light being run on every suitable night throughout the year, supplemented and/or replaced by the 125wt Mercury Vapour during the main part of the season.  The final species count was 629 (313 micro-moths, 316 macro-moths) which is actually just four short of the previous year’s record tally even though activity during the first half of 2016 seemed to be very slow indeed, far worse than in 2015, and suggested it would not be a vintage year.  The 30 micro and three macro species listed below proved to be new for the site list and they take the overall garden moth total to 906: 

 

4.002	Stigmella lapponica (mine on Birch)	25th June
4.007	Stigmella luteella (mine on Birch)	14th Oct
4.012	Stigmella aceris (mine on Norway Maple)	1st Nov
12.044	Haplotinea insectella *	17th July
15.056	Phyllonorycter salicicolella *	21st July
15.064	Phyllonorycter coryli (mine on Hazel)	9th Sept
15.076	Phyllonorycter emberizaepennella (mine on Snowberry)	10th Oct
15.081	Phyllonorycter nicellii (mine on Hazel)	5th Oct
20.007	Argyresthia cupressella *	20th June
20.015	Argyresthia curvella	20th June
28.024	Tachystola acroxantha *	16th July
30.001	Agnoea (Pseudatemelia) flavifrontella *	3rd June
34.012	Sorhagenia rhamniella *	20th July
35.143	Teleiodes luculella	10th June
37.011	Coleophora badiipennella *	21st July
38.046	Elachista albidella *	29th July
45.012	Stenoptilia pterodactyla *	27th July
48.002	Prochoreutis myllerana *	27th July
49.045	Eana osseana *	27th July
49.158	Hedya ochroleucana *	2nd Sept
49.289	Epiblema costipunctana *	24th July
49.307	Rhyacionia pinivorana	7th June
49.320	Dichrorampha alpinana *	20th July
62.012	Matilella (Pyla) fusca *	4th June
62.0151	Delplanqueia inscriptella *	15th July
62.021	Oncocera semirubella *	22nd Aug
62.064	Ephestia elutella *	25th July
63.042	Diplopseustis perieresalis *	21st July
63.048	Palpita vitrealis	3rd Sept
63.091	Agriphila latistria *	28th Aug
71.022	Maple Prominent Ptilodon cucullina	15th July
73.151	Webb’s Wainscot Globia sparganii	22nd Aug
73.215	Lesser-spotted Pinion Cosmia affinis *	24th Aug

* confirmed via dissection, with grateful thanks to Peter Hall.

Haplotinea insectella, Westcott 17th July

Diplopseustis perieresalis, Westcott 21st July

Agriphila latistria, Westcott 28th August

The three illustrated above, Haplotinea insectella, Diplopseustis perieresalis and Agriphila latistria, were all new species for Bucks.  With the expectation that I might well struggle to reach 600 species for the year (in the end something I needn’t have worried about), from September onwards particular attention was paid to searching for leaf-mines.  41 different species were identified this way in the garden, of which six proved to be new for the garden list.  For me the most interesting discovery was a vacated mine of Stigmella aceris on a fallen leaf beneath our Norway Maple.  This species is a fairly recent (1970s) colonist of the UK which is slowly spreading northwards but as yet doesn’t seem to be particularly common anywhere.  It was first recorded in Bucks during 2006 as an adult caught by the Rothamsted Insect Survey trap at Burnham Beeches.  There have been about 20 subsequent records, mostly as larval mines on Field Maple and Norway Maple and almost all from the southern half of the county.  For more about leaf-mines in the garden during 2016 follow this link.

 

Argyresthia curvella, Westcott 20th June

 

Sorhagenia rhamniella, Westcott 20th July

 

Prochoreutis myllerana, Westcott 11th August

 

Dichrorampha alpinana, Westcott 20th July

 

Prochoreutis myllerana appeared in the moth trap on four occasions between 27th July and 24th August, while on 5th September I found one resting during the daytime on a rudbeckia flower which by co-incidence was also being used by an example of its very common close relative Anthophila fabriciana (the Nettle-tap).  This made me wonder if I might perhaps have been overlooking the species in the past.  The larvae of myllerana feed on Skullcap which isn’t found in the garden although there are plenty of damp spots, ditches and ponds locally where this member of the mint family might thrive.

Maple Prominent was a very welcome addition to the garden list.  It seems to have a rather odd distribution in Bucks even though the larval food-plant Field Maple is ubiquitous.  The moth is widespread throughout the Chilterns and in the Milton Keynes area but appears to be largely absent from Aylesbury Vale and the northwest of the county.  Despite intensive trapping over the years, I’ve never found it in Bernwood Forest or any of the other associated ancient woodlands locally.

 

Maple Prominent, Westcott 15th July

 

The overall number of moths trapped in the garden during 2016 was 26,670.  That might seem a lot but it was actually a disappointing result, each of the previous three years having produced a higher total (27,438 in 2013; 32,910 in 2014; 33,941 in 2015).

 

Those macro-moth species which usually appear here in very large numbers suffered mixed fortunes during 2016.  A few ended up doing very well indeed, notably Brimstone Moth Opisthograptis luteolata, Large Yellow Underwing Noctua pronuba, Small Square-spot Diarsia rubi and Setaceous Hebrew Character Xesta c-nigrum which all achieved their highest ever garden totals.  However, rather more of them performed quite poorly compared to previous years, including Heart & Dart Agrotis exclamationis, Square-spot Rustic Xestia xanthographa, Lunar Underwing Omphaloscelis lunosa and Dark Arches Apamea monoglypha, along with the aggregate pairs of Common/Lesser Common Rustic Mesapamea secalis/didyma and Uncertain/Rustic Hoplodrina alsines/blanda.  None of the springtime Orthosia species did at all well apart from Hebrew Character Orthosia gothica, while the autumn Agrochola and Xanthia species also performed quite poorly although Black Rustic Aporophyla nigra, which flies at the same time of year, put in its best ever showing with 205 counted. 

 

Dusky Thorn Ennomos fuscantaria, supposedly one of our common species which is most under threat, was another moth which put in its best ever showing with 206 individuals seen.  Hopefully that can be sustained but the omens aren’t good due to the continued spread of the Chalara fungal disease which threatens its larval food-plant Ash Fraxinus excelsior.  Ash Die-back has already been found in my 10km square (link to map).

	Top 20 Highest Counts
20	Riband Wave	275
19	Lesser Broad-bordered Yellow Underwing	278
18	Agriphila tristella	316
17	Plutella xylostella	325
16	Dark Arches	341
15	Chrysoteuchia culmella	344
14	Hebrew Character	345
13	Common Footman	373
12	Smoky Wainscot	495
11	Flame Shoulder	533
10	Common Rustic (aggregate)	559
9	Brimstone Moth	583
8	Heart and Dart	629
7	Square-spot Rustic	699
6	Lunar Underwing	760
5	Small Square-spot	864
4	Uncertain/Rustic (aggregate)	1047
3	Setaceous Hebrew Character	1334
2	Acentria ephemerella	1424
1	Large Yellow Underwing	2086

 

Amongst the micros there was one very notable success story, that of Acentria ephemerella (Water Veneer) which during July, August and September amassed  a total of 1,424 individuals meaning that it came second only to Large Yellow Underwing in the year’s garden league table.  Although nowhere near those kind of numbers, Parapoynx stratiotata (Ringed China-mark) also did exceptionally well here in 2016 so the conditions locally may have favoured species whose larval stage is spent under water.

 

Acentria ephemerella, Westcott 18th September

 

Thanks to the newspapers predicting devastation of our brassica crops, Brussels Sprouts in particular, everyone will have heard about the mass invasion of Plutella xylostella (Diamond-back Moth) across the North Sea into the UK during late-May.  Westcott didn’t escape them although the final count for the year only reached 325, far fewer than many moth-trappers on the east coast achieved.  Several other micro-moth species which usually do very well here put in dismal performances during 2016.  The ‘grass moths’ were down considerably in numbers, Chrysoteuchia culmella and Agriphila straminella achieving only half of their previous year’s totals, while Agriphila tristella fell even further, down from 1,046 in 2015 to 316 in 2016.  Pleuroptya ruralis (Mother of Pearl) also put in a poor showing, dropping from 703 in 2015 to 196 in 2016.   

For migrant moths 2016 proved to be equally as good at Westcott as was the previous year, the only notable down-turn being that of Hummingbird Hawk-moth Macroglossum stellatarum which, unusually, was only recorded the once.  The table below gives first and last noted dates for those species which can be regarded as migrants here:

Plutella xylostella	325	9th May	10th October
Crocidosema plebejana	1	2nd January	-
Nomophila noctuella	51	11th May	29th October
Udea ferrugalis	43	8th July	24th September
Diplopseustis perieresalis	1	21st July	-
Palpita vitrealis	1	3rd September	-
Vestal	2	30th August	2nd September
Gem	1	6th July	-
Convolvulus Hawk-moth	1	28th September	-
Hummingbird Hawk-moth	1	27th June	-
Dark Sword-grass	6	9th September	14th November
Small Mottled Willow	1	17th August	-
Silver Y	110	4th June	30th October
Dark Spectacle	1	29th July	-

Palpita vitrealis, Westcott 3rd September

Convolvulus Hawk-moth with Lunar Underwing helpfully
providing scale, Westcott 28th September

Only two of the migrant species were newcomers to the garden list (Diplopseustis perieresalis and Palpita vitrealis).  The example of Crocidosema plebejana was presumably a remnant from the remarkable spate of moth immigration which took place over Christmas 2015 when, unfortunately, we were away. I wonder what I missed!

 

Garden Tiger, Westcott 12th July

 

One of the iconic moths of my youth when, unlike now, it was common everywhere in Bucks, Garden Tiger Arctia caja had only been recorded in the garden at Westcott once since the millennium and that was back in 2009.  I was therefore very pleased to get a second visitor on 12th July 2016.  It wasn’t to end there, though, because over the next fortnight I had four more appear in the garden trap.  I really hope that this is the start of a resurgence locally although somehow I doubt it.  2016 was really more noteworthy for the regulars which didn’t turn up in the garden, including Pale Eggar Trichiura crataegi, Lappet Gastropacha quercifolia, Brindled Green Dryobotodes eremita and Old Lady Mormo maura, while only the one Red Underwing Catocala nupta was seen when their count here often reaches double-digits.