Westcott, Bucks - the year 2018 in review

To put the site into context, these results come from an untidy rural village garden in grid square SP7117 out on the heavy clay of Aylesbury Vale.  Native trees and shrubs within and around the edge of the garden include virtually all of the common species which are to be found growing wild in the local area, apart from oak.  Adjacent to us are other mature gardens, a churchyard and sports field as well as farmland (mostly grazing pasture).  There are several ponds nearby and a decent network of ditches along with plenty of ancient hedgerows, a few of which are hacked to death annually but many others are left nicely unkempt.  The closest parts of the former Westcott airfield, now an industrial park, are turning into secondary woodland and much of the site’s boundary fence is lined with mature poplars.  On the far side of the airfield is a disused railway cutting with its own unique habitat although this is slowly being lost to scrub.  A mile to the east can be found the manicured grounds of Waddesdon Manor, while a mile to the north-west there is mixed deciduous plantation woodland covering an old landfill site.  A small amount of mature oak woodland lies a mile to the south but there is much more of it within a radius of five miles.  Bernwood Forest is seven miles away as the crow flies and the scarp slope of the Chiltern Hills is just under ten miles away at its closest point.      

Butterflies

While 2018 was reasonable for butterflies in the garden, it wasn’t a vintage year.  21 species were recorded, the first being a Small Tortoiseshell Aglais urticae tempted out of hibernation on 17th February and the last a Red Admiral Vanessa atalanta visiting ivy blossom on 21st October.  The only obvious absentees were Small Skipper Thymelicus sylvestris and Essex Skipper Thymelicus lineola and in fact one or other did visit briefly on 15th July but I wasn’t quick enough to identify it properly.  Small Heath Coenonympha pamphilus appeared again after an absence of five years, a single second-brood specimen visiting our cat-mint on 9th September.  Although quite widespread in the local countryside, the species rarely finds its way into the garden.



Small Heath, Westcott 9th September 2018

Star of the show once again was White-letter Hairstreak Satyrium w-album which was recorded regularly on our surviving garden elms over a four-week period between 23rd June and 19th July.  Unusually, on 10th July I had camera in hand when a female landed on the lawn and went walk-about for a few minutes.  It was not immediately clear what she was searching for!



White-letter Hairstreak, Westcott 10th July 2018

At least one female Brown Hairstreak Thecla betulae must have come very close once again because on 5th October an egg was found on blackthorn less than 50 metres away in a hedge surrounding the adjacent churchyard, but it is four years now since the last sighting of an adult actually within the garden.

The buddleias didn’t attract many vanessids during the summer and neither did our ivy blossom later in the year.  While it was good to see singletons of the migrant Painted Lady Vanessa cardui on half a dozen occasions between July and September, the resident Red Admirals achieved a high of only six individuals at any one time, Peacock Aglais io a maximum of two (present only over three consecutive weeks in July), Small Tortoiseshell just four and Comma Polygonia c-album a maximum of three at once.  Those are very disappointing numbers.  Other common summer species such as Meadow Brown Maniola jurtina and Gatekeeper Pyronia tithonus were around in lower numbers than usual and seemed to finish quite quickly, the one exception being Speckled Wood Pararge aegeria which for a change was recorded here regularly in every month between April and September.  

The Mothing Year

2017 might have been a fantastic year for moths at Westcott but 2018 proved to be an even better one!  The overall catch amounted to just over 42,000 individuals, which is half as many again as the previous year and significantly more than the previous record of 33,941 in 2015.  The twin-30wt actinic trap was deployed in the garden on every suitable night that I was here (295 in all, roughly comparable to previous years).  Most of the missing nights were due to harsh winter conditions between early January and the end of March and then holiday absences in May and September.  The difference in 2018 was the number of occasions on which the 125wt Mercury Vapour trap was run in addition to the actinic (87 nights, as opposed to 32 in 2017).  Using the two different types of light in tandem certainly paid dividends, particularly during the busiest months of June and July, even though they were placed only ten metres apart (separated from each other by a fairly thick hedge).  100 species in one night was exceeded on 26 occasions during those two months and 150 species was exceeded three times, the best catch of the year being on 4th July when 165 different species turned up to the two lights (660 individual moths of 126 species to the MV, 353 of 93 species to the actinic).

	Top 20 Highest Counts, 2018
1	Setaceous Hebrew Character	1819
2	Acentria ephemerella	1798
3	Heart and Dart	1571
4	Large Yellow Underwing	1366
5	Lunar Underwing	1190
6	Common Footman	1126
7	Square-spot Rustic	1077
8	Flame Shoulder	1060
9	Patania (Pleuroptya) ruralis	975
10	Smoky Wainscot	874
11	Yponomeuta evonymella	856
12	Dark Arches	789
13	Agriphila straminella	722
14	Straw Dot	719
15	Agriphila tristella	694
16	Brimstone Moth	684
17	Vine's Rustic	639
18	Beaded Chestnut	496
19	Chrysoteuchia culmella	462
20	Black Rustic	421

For a change it was Setaceous Hebrew Character Xestia c-nigrum which topped the leader board with 1,819 individuals caught between 20th May and 6th November.  As expected, Heart and Dart Agrotis exclamationis (1,571) and Large Yellow Underwing Noctua pronuba (1,366) also performed well but they were unexpectedly relegated to third and fourth place behind the aquatic micro-moth Acentria ephemerella (1,798) which came second.  A further five micros achieved a spot in the top 20, including Mother of Pearl Patania (Pleuroptya) ruralis which at 975 only just failed to break the thousand barrier and Bird-cherry Ermine Yponomeuta evonymella which did exceptionally well to reach 856. 

Of the aggregate species shown below, Common Rustic Mesapamea secalis, Uncertain Hoplodrina alsines and Rustic Hoplodrina blanda would certainly have gained a place somewhere in the top 20 if they had all been identified to species.

	Aggregate Counts, 2018
1	Oligia species (Minors)	439
2	Hoplodrina species (Uncertain & Rustic)	1313
3	Mesapamea species (Common/Lesser Common Rustic)	1476

 

As far as individual moth species are concerned the total achieved over the year came to 685 (345 micros and 340 macros - the full species list can be viewed here), better even than the 662 recorded in 2017 and must be just about on the limit of what is possible here in a single year.  The all-time garden lepidoptera list, accumulated post-millennium, now stands at 1002 species (971 moths, 31 butterflies) with the following 35 new additions for 2018:

 

4.053	Stigmella incognitella (mine on Apple)	20 Oct
4.058	Stigmella basiguttella *	2 Aug
4.078	Ectoedemia septembrella *	9 July
4.090	Ectoedemia subbimaculella *	11 June
16.022	Cedestis subfasciella *	1 July
32.021	Agonopterix assimilella *	22 Aug
35.019	Anarsia innoxiella *	3 July
35.101	Gelechia sororculella *	21 June
37.036	Coleophora conyzae *	4 July
37.104	Coleophora adspersella *	1 July
38.025	Elachista atricomella *	21 July
45.011	Amblyptilia punctidactyla *	23 June
45.028	Capperia britanniodactylus *	28 June
49.014	Archips crataegana *	17 June
49.087	Acleris literana	11 Mar
49.108	Gynnidomorpha alismana *	14 July
49.162	Celypha rosaceana *	3 July
49.195	Bactra furfurana *	19 July
49.318	Dichrorampha vancouverana *	23 July
49.347	Grapholita compositella	21 July
49.356	Grapholita lobarzewskii *	11 June
49.358	Grapholita tenebrosana *	26 June
62.053	Ancylosis oblitella *	4 Aug
63.047	Spoladea recurvalis	15 Oct
63.118	Nymphula nitidulata *	6 July
63.120	Chilo phragmitella *	4 July
70.174	Pinion-spotted Pug Eupithecia insigniata *	7 May
71.001	Oak Processionary Thaumetopoea processionea	19 July
72.030	Jersey Tiger Euplagia quadripunctaria	31 July
72.041	Four-spotted Footman Lithosia quadra	14 July
73.072	Marbled Clover Heliothis viriplaca	26 July
73.137	Fen Wainscot Arenostola phragmitidis	4 July
73.302	Obscure Wainscot Leucania obsoleta	25 Jun
73.332	Purple Clay Diarsia brunnea	13 Jun
74.011	Cream-bordered Green Pea Earias clorana	9 July

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

Micro-moths

Not a lot of effort was put into searching for leaf-mines during 2018 and only 30 different species were recorded in the garden at that stage of their life cycle.  Just the one was new, a single mine of Stigmella incognitella  found on our domestic apple during October.  Considering how widespread its food-plant is, especially in gardens, this seems to be a genuinely uncommon moth in Bucks.  In the photo below the fully-grown larva (orange-yellow body, brown head) can be seen feeding in the central blotch.  Ignore the thinner corridor mine with broken frass running from bottom to top on the left side as that is the ubiquitous Lyonetia clerkella mining the same leaf.

Mine of Stigmella incognitella, Westcott 20th October 2018

On the other hand, an adult Stigmella basiguttella in the garden was a big surprise because, despite being a relatively common species, oak is in short supply locally and I can’t imagine such a tiny moth flying all that far from its foodplant.

The two Coleophorids take the number of species from that family recorded in the garden to 41, all confirmed by dissection.  Coleophora conyzae (whose larvae feed on Hemp-agrimony, Ploughman’s-spikenard and Common Fleabane) is only the second record for Bucks.  Until 2018 there were only four county records of Agonopterix assimilella, all from the greensand ridge on the Bedfordshire border where the larval foodplant Broom is fairly widespread.  The moth is probably under-recorded in the county because I had it in some numbers in Rowley Wood near Black Park during 2018, where there is also a large amount of Broom, but the plant isn’t at all common on the clay so the garden sighting at Westcott will probably have been associated with cultivated varieties.  The Gelechid Anarsia innoxiella seems to be a species on the move because in 2018 I had three individuals in the garden between 3rd and 8th July.  It is a fairly recent split from the pest species Peach Twig Borer Anarsia lineatella.  Adding two more Plume species to the garden list was also very pleasing.  Capperia britanniodactylus is uncommon in Bucks with only five previous records, four from Burnham Beeches and the other from Stoke Common.  Its larval foodplant is Wood Sage, for which the on-line BSBI distribution maps show no records at all for my 10km square SP71, but this perennial is widespread throughout the UK and is sometimes grown in gardens.  The other moth, Amblyptilia punctidactyla, doesn’t come as a surprise because its larvae feed on Hedge Woundwort of which we have plenty in the garden.

 

Capperia britanniodactylus, Westcott 28th June 2018

 

The tortricoid moths Gynnidomorpha alismana, Celypha rosaceana, Bactra furfurana & Grapholita compositella have been recorded previously in this general area (C. rosaceana closest of all, from the disused railway cutting west of Westcott) so they’re not unexpected in the garden.  However, the other two Grapholita species, lobarzewskii and tenebrosana, are both rare in Bucks with only three previous county records for each of them, while Dichrorampha vancouverana is supposedly a widespread moth but in VC24 there have been only two previous sightings, both in the same lay-by on the A41 east of Aston Clinton, right on the border with Herts.  Ancylosis oblitella is a migrant which became established in south-east England in the 1950s and has been slowly spreading northwards.  There is one previous Bucks record (in 2003 from Milton Keynes) but it looks as though the moth may now be here to stay as four were trapped in the garden during August 2018.  Beautiful China-mark Nymphula nitidulata is the least common of the China-mark moths and finally “completes the set” for the garden, two being recorded on 6th July and a third following on 22nd August. 

 

Gynnidomorpha alismana, Westcott 14th July 2018



Grapholita compositella, Westcott 21st July 2018



Grapholita lobarzewskii, Westcott 11th June 2018



Ancylosis oblitella, Westcott 4th August 2018

 

Of the micros which weren’t first timers it was particularly good to see Eana incanana once again (26th June), the first garden example for ten years of this moth which is associated with bluebells.  In addition, Sorhagenia rhamniella (1st July) and Epinotia nanana (11th June & 7th July) have each been recorded here only once previously.

 

Macro-moths

 

To get nine new macro-moth species was unexpected, especially having had the exact same number of new ones in 2017.  The garden macro list now stands at 432 and you would have thought that, by now, getting new ones would be a rare event.  However, the Bucks all-time macro-moth list is hovering around the 630 mark (albeit including some 60 or so which haven’t been recorded since the millennium and may well now be extinct in the county), so there is certainly still the potential for further species to turn up.  In particular there are a number of moths known to be on the move in our region which hopefully might reach the garden within a few years, Dewick’s Plusia Macdunnoughia confusa, Toadflax Brocade Calophasia lunula, Black-spotted Chestnut Conistra rubiginosa, Oak Rustic Dryobota labecula, Clancy’s Rustic Caradrina kadenii and L-album Wainscot Mythimna l-album to name but a few.  

The nationally scarce Pinion-spotted Pug visited twice, the second example coming to light on 21st May and that is the one illustrated below because the first wasn’t in pristine condition.  There are 20 previous sightings for Bucks, many from the area around Milton Keynes, but only seven are post-millennium and those at Westcott are the first records since 2010 which seems to fit with the literature in that the moth is “seldom seen”.  Males of the potential pest species Oak Processionary appeared in the trap three times over the period of a week in July and I’m sure the moth must now be here to stay no matter how hard the Forestry Commission is trying to eradicate it.

     

Pinion-striped Pug, Westcott 21st May 2018



Oak Processionary, Westcott 19th July 2018

 

The smart Jersey Tiger was of the form lutescens with yellow rather than red hind-wings and was expected at Westcott sooner or later.  However, Marbled Clover (a first for Bucks) certainly wasn’t expected and it is unclear where that moth will have come from.  A Red Data Book species resident mainly in the breckland area of East Anglia, it is also known to have strong migratory tendencies.



Jersey Tiger f. lutescens, Westcott 31st July 2018



Marbled Clover, Westcott 14th July 2018

 

The Lasiocampids did particularly well here in 2018, with December Moth Poecilocampa populi, Pale Eggar Trichiura crataegi, Lackey Malacosoma neustria, Drinker Euthrix potatoria  and Lappet Gastropacha quercifolia all achieving their best ever garden totals, while both Oak Eggar Lasiocampa quercus and Fox Moth Macrothylacia rubi put in single visits once again.  Of the Geometrid moths, Dark Spinach Pelurga comitata returned to the trap on 23rd July following its only other visit here back in 2012, while the three commonest Pug species, Double-striped Gymnoscelis rufifasciata, V-Pug Chloroclystis v-ata and Lime-speck Eupithecia centaureata, all managed record-breaking totals. 

Garden Tiger Arctia caja put in five appearances, the third year in a row that this fast declining but formerly widespread species has graced the trap, so there must still be a small residual population locally.  Red-necked Footman Atolmis rubricollis made only its second appearance after the first in 2013, while Clifden Nonpareil Catocala fraxini visited once again after joining the garden list in 2017.  Gold Spot Plusia festucae had a fantastic season with 88 of them recorded in the garden between 10th June and 10th October.  I’ve never before had a double-digit annual count nor seen any daytime activity from the species.



Gold Spot, Westcott 4th August 2018



A single Bordered Sallow Pyrrhia umbra was trapped on 29th June, making its first visit to the garden since 2007.  Rosy Minor Litoligia literosa, presumably a stray from the Chilterns, put in another appearance on 4th August, the first to be seen here for five years.  The elm-feeding Lesser-spotted Pinion Cosmia affinis was first recorded in the garden during 2016 but sadly none appeared the following year.  However, in 2018 I had no less than ten of them between 12th July and 5th August, so hopefully it has re-established itself locally.  Finally, on 15th September I was pleased to find Large Ranunculus Polymixis flavicincta in the trap once again, the first garden record since 2011.

Finding moths that didn’t do well in 2018 has been a challenge.  There were just two unexpected absentees from the traps, Nutmeg Anarta trifolii and Shears Hada plebeja.  They are two closely-related species which can normally be relied upon to make a handful of visits each year.  Both are double-brooded locally which makes their complete absence even more surprising.  Common Swift Korscheltellus lupulina had a relatively poor season and I was disappointed not to see Dotted Fan-foot Macrochilo cribrumalis after a run of five consecutive years of garden records.

During the second half of 2018 some noticeably smaller-than-usual moths began to appear in the trap, illustrated well by the normal and pint-sized Lime-speck Pugs in the picture below.  In some cases this may well have been caused by the dessication of their food-plant materiel during the very hot summer, resulting in larvae being forced to attempt pupation before they would normally have done so. 

 

Lime-speck Pugs, Westcott 23rd July 2018



 

Migrant Moths

 
It was a reasonable year for migrants at Westcott and two or three notable species did visit the garden, although the usually common Rusty-dot Pearl Udea ferrugalis and Rush Veneer Nomophila noctuella made only a single visit each.  Pride of place must go to the smart Crambid Spoladea recurvalis on 15th October which was not only a first timer here but was also a first for Bucks.  It is not a common migrant, rarely getting beyond the coast, but in October 2018 many examples were seen inland and they included first county records for Beds and Herts as well as Bucks.  Four-spotted Footman was another first-time visitor to the garden, while Palpita vitrealis was the second of that species to appear after one the previous year.  Dark Sword-grass Agrotis ipsilon had its best year ever here (and produced my first December records of the species) but one wonders if some may actually have been home-grown individuals rather than migrants.  The same is true of Dark Spectacle Abrostola triplasia which is appearing more often in the county nowadays and may be in the process of becoming established.  On the other hand, the resident Turnip Moth Agrotis segetum did unexpectedly well with 117 individuals recorded in the garden between May and November (38 was the previous highest annual count here).  During 2018 its numbers will almost certainly have been boosted by immigration, especially during the autumn.

Spoladea recurvalis, Westcott 15th October 2018



Four-spotted Footman, Westcott 14th July 2018

 One thing of particular note in 2018 was the record number of visits from the enchanting Hummingbird Hawk-moth Macroglossum stellatarum which had its best ever year here.  There were many occasions when two appeared at the same time on the buddleia outside our kitchen window and three were seen together there on three separate dates in August.  It was one species which the rest of the family showed some interest in and those extra pairs of eyes certainly helped the records to accumulate.  Silver Y Autographa gamma also did well during the year but didn’t beat the totals achieved here in 2006 or 2013.  To conclude, the table below gives totals along with first and last sighting dates for the migrants recorded at Westcott in 2018: 

 

Plutella xylostella	48	25th May	21st Dec
Udea ferrugalis	1	15th Nov	-
Spoladea recurvalis	1	15th Oct	-
Palpita vitrealis	1	12th Oct	-
Nomophila noctuella	1	7th Aug	-
Vestal	2	13th Oct	16th Oct
Hummingbird Hawk-moth	75	11th Jul	29th Sep
Four-spotted Footman	1	14th Jul	-
Dark Sword-grass	29	9th Jul	6th Dec
Scarce Bordered Straw	1	13th Aug	-
Silver Y	226	24th May	22nd Dec
Dark Spectacle	3	4th July	20th July