Newhaven's Butterflies and Moths: May 2016

Butterflies and moths recorded during May 2016 

 

Vine's Rustic (Hoplodrina ambigua)

There has in recent posts been a burgeoning use of the word average. May was, until the 29th, an average month. That is how it felt anyway. Average when compared with the records I have collected in all the months of May since I began recording moths and butterflies at home and in the field. The start of May 2016 was nice and warm but a northerly airflow dominated after this and temperatures were generally cool - dare I say below average.

So let's take a look at some Maytime averages, starting at the moth trap. Over the years I have operated my trap 21 nights of the month on average - on about two out of every three nights. This year I ran my moth trap every night during May.

I have recorded a total of 345 butterfly and moth species during previous May-times, with an average of 133 species each year and 1356 individuals. This May I saw a slightly above average 150 species and 1613 individuals. Thirteen of the species recorded had not previously been seen during May-time. Of the ten most abundant species seen this year, some were on a par with the previous ten years' average: Heart and Dart (110), Dingy Skipper (51), Shuttle-shaped Dart (42) and Small White (42); but three of the remaining species were significantly more numerous this May than in the past: Diamond-back Moth (202) (average 9), Light Brown Apple Moth (119) (average 38) and White-shouldered House Moth (43) (average 6).

There are good reasons why the Diamond-back and White-shouldered House Moth were so much more abundant this year: the first is currently undergoing a mass immigration from the continent - probably the greatest example in the Sussex record (the total of 202 was the thin end of the wedge, the tip of the iceberg, the i of the idiom)  - and the second was more numerous because adults were emerging from either a sack of grass clippings which was being stored in my shed or from a mouse nest beneath the shed which I have been tolerating (I like mice). Part of my evening ritual each night was to pot up fresh adults (moths, not mice) from the inside of the shed window and release them into the garden - many of whom eschewed the moth trap light and flew elsewhere, never to be seen again. One interesting observation made of these moths was the dimorphism between individuals (see the photograph below for an example). The third species which was much more numerous than its average number, the Light Brown Apple Moth, an adventive species accidentally introduced to the UK from Australia in the 1950s and now a pest of orchards, is less easy to explain. One assumes it has benefitted from the mild winter. It has had an above average year.

An example of dimorphism in the White-shouldered House Moth (Endrosis sarcitrella)

Amongst the four migrant species seen, the Diamond-back and Red Admiral were much more numerous than usual, whereas the Silver Y and White-point were seen very much in average numbers.

Five-spot Ermel (Ethmia terminella)

The nationally scarce species of moths and butterflies I saw were few. The Duke of Burgundy and Adonis Blue were seen away from Newhaven at Heyshott and Mill Hill respectively. Of the three moths, Ethmia terminella was by far the most welcome and only the second individual I have ever seen. Aethes williana and Platyedra subcinerea are always a welcome sight, but Newhaven is blessed with established colonies and their appearance each year.

There is one final point to make about averages, and that is that I put in an above average effort this May. I ran the trap each night, walked two transect routes at Castle Hill LNR, surveyed four other locations around Newhaven and enjoyed guided walks at Heyshott, Shoreham's Mill Hill and Newhaven's Bollen's Bush. It's hardly work though, is it?

As a postscript regarding the Diamond-back Moth immigration, I have during the first week of June seen more than 11,000 individuals, 4500 of which have been counted in my moth trap. I can predict with some confidence, therefore, that June is looking decidedly above average.

Rustic Shoulder-knot (Apamea sordens)

The full list for May 2016

Butterflies (20 species)

Dingy Skipper (Erynnis tages)  51

Grizzled Skipper (Pyrgus malvae)  14

Orange-tip (Anthocharis cardamines)  11

Large White (Pieris brassicae)  10

Small White (Pieris rapae)  42

Green-veined White (Pieris napi)  10

Brimstone (Gonepteryx rhamni)  36

Wall (Lasiommata megera)  8

Speckled Wood (Pararge aegeria)  17

Small Heath (Coenonympha pamphilus)  6

Red Admiral (Vanessa atalanta)  39

Peacock (Aglais io)  7

Small Tortoiseshell (Aglais urticae)  12

Duke of Burgundy (Hamearis lucina)  46 – seen away from Newhaven at Heyshott Down near Midhurst

Green Hairstreak (Callophrys rubi)  30

Small Blue (Cupido minimus)  1

Holly Blue (Celastrina argiolus)  14

Brown Argus (Aricia agestis)  1

Common Blue (Polyommatus icarus)  5

Adonis Blue (Polyommatus bellargus)  1

Moths (130 species)

Buff Long-horn (Nematopogon metaxella)  4
Green Long-horn (Adela reaumurella)  11
Five-spot Burnet (Zygaena trifolii)  2
Skin Moth (Monopis laevigella)  1
Yellow-backed Clothes (Monopis obviella)  6
Case-bearing Clothes Moth (Tinea pellionella)  1
Common Slender (Caloptilia syringella)  9
Common Nettle-tap (Anthophila fabriciana)  14
Apple Leaf Skeletoniser (Choreutis pariana)  1
Cocksfoot Moth (Glyphipterix simpliciella)  20
Cypress-tip Moth (Argyresthia cupressella)  1
Hawthorn Ermel (Paraswammerdamia nebulella)  4
Diamond-back Moth (Plutella xylostella)  202
Gorse Case-bearer (Coleophora albicosta)  1
Brown House Moth (Hofmannophila pseudospretella)  6
White-shouldered House Moth (Endrosis sarcitrella)  43
Sulphur Tubic (Esperia sulphurella)  10
Common Tubic (Alabonia geoffrella)  3
Parsnip Moth (Depressaria heraclei)  2
Small Purple Flat-body (Agonopterix purpurea)  1
Ruddy Flat-body (Agonopterix subpropinquella) 1
Brown-spot Flat-body (Agonopterix alstromeriana)  4
Five-spot Ermel (Ethmia terminella)  1
Dark Groundling (Bryotropha affinis)  2
Mallow Groundling (Platyedra subcinerea)  1
Vetch Sober (Aproaerema anthyllidella)  1
Garden  Cosmet (Mompha subbistrigella)  6
Common Cosmet (Mompha epilobiella)  1
Violet Cosmet (Pancalia leuwenhoekella)  1
Rough-winged Conch (Phtheochroa rugosana)  1
Common Yellow Conch (Agapeta hamana)  1
Silver Carrot Conch (Aethes williana)  3
Yarrow Conch (Aethes smeathmanniana)  2
Red-fringed Conch (Falseuncaria ruficiliana)  13
Black-headed Conch (Cochylis atricapitana)  6
Light Brown Apple Moth (Epiphyas postvittana)  119
Red-barred Tortrix (Ditula angustiorana)  1
Yellow-spot Twist (Pseudargyrotoza conwagana)  4
Common Marble (Celypha lacunana)  3
Marbled Orchard Tortrix (Hedya nubiferana)  1
Teasel Marble (Endothenia gentianaeana)  1
Smoky-barred Marble (Lobesia abscisana)  2
Yellow-faced Bell (Epiblema cynosbatella)  12
Thistle Bell / Knapweed Bell agg. (Epiblema cirsiana/scutulana)  3
Fruitlet Mining Tortrix (Pammene rhediella)  2
Grey Gorse Piercer (Cydia ulicetana)  62
Codling Moth (Cydia pomonella)  2
Lead-coloured Drill or Obscure Drill (Dichrorampha plumbana / aeratana ) 116
Twenty-plume Moth (Alucita hexadactyla)  2
Meadow Grey (Scoparia pyralella)  2
Narrow-winged Grey (Eudonia angustea)  20
Garden Pebble (Evergestis forficalis)  5
Small Purple & Gold (Pyrausta aurata)  6
Common Purple & Gold (Pyrausta purpuralis)  2
Straw-barred Pearl (Pyrausta despicata)  3
Wavy-barred Sable (Pyrausta nigrata)  11
Small Magpie (Eurrhypara hortulata)  2
Common Plume (Emmelina monodactyla)  3
Lackey (Malacosoma neustria)  2 larvae
Oak Eggar (Lasiocampa quercus)  1 larva
Emperor Moth (Saturnia pavonia)  7
Chinese Character (Cilix glaucata)  1
Clay Triple-lines (Cyclophora linearia)  2
Red Twin-spot Carpet (Xanthorhoe spadicearia)  2
Garden Carpet (Xanthorhoe fluctuata)  3
Common Carpet (Epirrhoe alternata)  13
Streamer (Anticlea derivata)  2
Purple Bar (Cosmorhoe ocellata)  2
Common Marbled Carpet (Chloroclysta truncata)  1
Green Carpet (Colostygia pectinataria)  8
Mottled Pug (Eupithecia exiguata)  3
Lime-speck Pug (Eupithecia centaureata)  3
Freyer's Pug (Eupithecia intricata)  1
Currant Pug (Eupithecia assimilata)  4
Common Pug (Eupithecia vulgata)  4
White-spotted Pug (Eupithecia tripunctaria)  7
Brindled Pug (Eupithecia abbreviata)  1
Dwarf Pug (Eupithecia tantillaria)  1
V-Pug (Chloroclystis v-ata)  3
Green Pug (Pasiphila rectangulata)  2
Double-striped Pug (Gymnoscelis rufifasciata)  23
Lesser Treble-bar (Aplocera efformata)  3
Brimstone Moth (Opisthograptis luteolata)  23
Early Thorn (Selenia dentaria)  1
Peppered Moth (Biston betularia)  1
Waved Umber (Menophra abruptaria)  9
Common Heath (Ematurga atomaria)  1
Yellow Belle (Semiaspilates ochrearia)  2
Privet Hawk-moth (Sphinx ligustri)  1
Poplar Hawk-moth (Laothoe populi)  3
Small Elephant Hawk-moth (Deilephila porcellus)  2
Buff-tip (Phalera bucephala)  1
Swallow Prominent (Pheosia tremula)  1
Coxcomb Prominent (Ptilodon capucina)  1
Chocolate-tip (Clostera curtula)  2
Brown-tail (Euproctis chrysorrhoea)  1 larval tent – having a poor season
Orange Footman (Eilema sororcula)  3
White Ermine (Spilosoma lubricipeda)  4
Buff Ermine (Spilosoma luteum)  3
Muslin Moth (Diaphora mendica)  3
Ruby Tiger (Phragmatobia fuliginosa)  2
Cinnabar (Tyria jacobaeae)  6
Least Black Arches (Nola confusalis)  7
Heart and Dart (Agrotis exclamationis)  110
Shuttle-shaped Dart (Agrotis puta)  42
Flame Shoulder (Ochropleura plecta)  8
Large Yellow Underwing (Noctua pronuba)  8
Setaceous Hebrew Character (Xestia c-nigrum)  3
Shears (Hada plebeja)  23
Cabbage Moth (Mamestra brassicae)  2
Light Brocade (Lacanobia w-latinum)  9
Bright-line Brown-eye (Lacanobia oleracea)  11
Powdered Quaker (Orthosia gracilis)  1
Common Quaker (Orthosia cerasi)  6
Hebrew Character (Orthosia gothica)  11
White-point (Mythimna albipuncta)  1
Mullein (Shargacucullia verbasci)  5
Early Grey (Xylocampa areola)  2
Grey Dagger / Dark Dagger (Acronicta tridens/psi)  1
Angle Shades (Phlogophora meticulosa)  10
Rustic Shoulder-knot (Apamea sordens)  3
Marbled Minor agg. (Oligia strigilis agg.)  3
Treble Lines (Charanyca trigrammica)  1
Vine's Rustic (Hoplodrina ambigua)  23
Oak Nycteoline (Nycteola revayana)  1
Silver Y (Autographa gamma)  12
Spectacle (Abrostola tripartita)  5
Mother Shipton (Callistege mi)  1
Burnet Companion (Euclidia glyphica)  2

Early June at Newhaven's Castle Hill LNR: continental visitors arrive

Week 10 of the 2016 transect-walking season

 

Butterfly numbers were again lower than expected with only seven species seen during the walk. The weather during the walk was warm and sunny with only light winds, but this was the first day in a while that the weather was not cool, cloudy and windy. Despite the tendency to think that numbers are poor, upon comparison with most other years numbers are about average - and one species, the Green Hairstreak (Callophrys rubi) has already had its best year to date. Eighteen butterfly species have been recorded so far during 2016.

Diamond-back Moth (Plutella xylostella)

Two overseas species spiced up proceedings: the tiny Diamond-back Moth (Plutella xylostella) and the much larger - and much more noticeable - Painted Lady (Vanessa cardui). The latter was seen flying in off the sea in a northerly direction and these are possibly the vanguard of a greater immigration which may occur over the coming days. These are a strong, unmistakeable insect and there is always a hope that the event of 2008 will be repeated, when many, many millions of these butterflies piggybacked across three generations from the African Atlas Mountains into the UK and as far north even as the Arctic Circle, before their offspring made the return journey back south at the end of their season. 

The Diamond-back Moth is in the midst of a similar immigration event, which hit Newhaven on 30th May, but apparently from the east rather than from southerly climes. I have recorded more than ten thousand of these moths in Newhaven during the past week and I saw an additional 400 - well, 398 - during this walk. Many of these were nestled amongst hoary cress and kale along the cliff bottom and their caterpillars will feed on these and other plants of the cabbage family during the summer. There were without doubt many thousands more than the 400 that I counted, but transect-walking rules are not to be broken, so I counted only what flew up before me as I stepped along the route! I have written a separate report about the Diamond-back Moths which provides more information about this tiny species and the current immigration event.

Large Skipper (Ochlodes faunus)

Whilst these and other exotic species add colour to the nature reserve, we are inevitably more interested in the native species which breed each year at Castle Hill. Numbers fluctuate annually, in response to many variable and confounding factors, and not least the weather. These species have evolved to take the knocks and then make hay when conditions are more favourable. This year is proving to be more or less average when compared with some previous years. It was pleasing to see the emergence of the Large Skippers (Ochlodes faunus), albeit in only small numbers, but these feisty little butterflies, which lay their eggs on Cocksfoot grass, should increase in number during the next few weeks. Common Blue (Polyommatus icarus) numbers are increasing by the week and the first brood should peak in the next two or three weeks, as should the day-flying moths the Mother Shipton (Euclidia mi) and Burnet Companion (Euclidia glyphica), which can be found amongst herbaceous areas along the tops of the cliffs.

Earlier in the year I made a chance observation of a Raven raiding the Barrow Head cliff face hollows which are used as nest holes by a small group of Jackdaws and feral pigeons. The Jacks were perturbed and apparently helpless on that occasion as the Raven leered menacingly into each hole, but there was nothing to steal away at the time (egg-laying time was still in the future) and it flew off empty-handed. I witnessed a repeat raid today, probably by the same Raven. The response of the Jacks could not have been more different: whereas they previously appeared to yield helplessly to their preponderant corvine cousin, today they were a tight fighting force. Arranged in formation they swooped in turn, five Jacks deep, to mob their attacker, they swarmed around, jostled, grappled, set upon, overran and comprehensively saw it off. Within the space of thirty seconds the egg thief was utterly routed. It was spectacular stuff! The Jacks had a most valuable resource to lose this time in their chicks, which must now be very close to fledging. I think this is an example of the concept in the study of behavioural ecology known as the incumbency advantage.

Krebs & Davies (1993) eloquently explained at length how an incumbent (or owner of a resource) has an advantage over a challenger because the incumbent knows or understands the resource at stake, whereas the rival does not possess such detailed knowledge. I am not a behavioural ecologist, but I believe the battle over the Jackdaw chicks (the resource) was an example of this. The investment by the several adults and the bonds with the chicks resulted in a much greater challenge to the Raven than when their nest holes were empty. The hypothesis of the incumbent advantage is that the owner will fight more strongly than the less certain challenger and almost always win. Also, they have more to lose than the predator has to gain. The stakes vary and there are plenty of examples in nature when the predator wins the prey, but I was stunned and mightily impressed by the ferocity of the parent birds on this occasion.

The reserve is easing itself into the summer season now. Grasses are shooting skywards and flowering, along with Thrift and the Common Blue's food-plant Bird's-foot Trefoil on and above the cliff faces. There are the usual concerns about humans' conflicting interests and multiple uses of the nature reserve, but I am not going to bore the reader with a personal diatribe until I have taken the time to convey my feelings - my disgust even - in a more positive light.

The full list for Week 10 (24 species)

Butterflies (7 species) Large Skipper (Ochlodes sylvanus)  3
Small White (Pieris rapae)  1
Green-veined White (Pieris napi)  1
Speckled Wood (Pararge aegeria)  2
Small Heath (Coenonympha pamphilus)  1
Painted Lady (Vanessa cardui)  9
Common Blue (Polyommatus icarus) 12
Moths (17 species) Diamond-back Moth (Plutella xylostella)  398
Common Tubic (Alabonia geoffrella)  1
Light Brown Apple Moth (Epiphyas postvittana) 1
Common Marble (Celypha lacunana)  3
Plum Tortrix (Hedya pruniana)  5
Knapweed Bell (Epiblema cirsiana)  1
Regal Piercer (Pammene regiana)  1 – first site record
Grey Gorse Piericer (Cydia ulicetana)  15
Lead-coloured Drill (Dichrorampha plumbana)  1
Garden Grass-veneer (Chrysoteuchia culmella)  1
Meadow Grey (Scoparia pyralella)  1
Little Grey (Dipleurina lacustrata)  2
Lackey (Malacosoma neustria)  1
Yellow Belle (Semiaspilates ochrearia)  1
Angle Shades (Phlogophora meticulosa)  1
Mother Shipton (Callistege mi)  1
Burnet Companion (Euclidia glyphica) 4
Other highlights Grove or Brown-lipped Snail (Cepaea nemoralis)  1 – not previously found at CHLNR
22-spot Ladybird (Psyllobora vigintiduopunctata)  1
Dock Bug (Coreus marginatus)  7
Green Shield-bug (Palomena prasina)  1

Common Tubic (Alabonia geoffrella)

Garden Grass-veneer (Chrysoteuchia culmella)

An invasion of the Diamond-back Moth

May 2016 in Newhaven felt decidedly average when considered from a butterfly and moth perspective - until after the 29th. The final two days of the month saw an explosion in numbers of a tiny migrant micro-moth species: the Diamond-back Moth Plutella xylostella.

Individual Diamond-backs began to appear in my garden moth trap this year from 6th May and continued in this manner every few days until 23rd, when they disappeared for a week. Then, on 30th, I saw twenty. The most I had ever recorded during one night before was 64, so twenty individuals gained my attention as it was a comparatively noteworthy number. The nights following this produced the following numbers:

31st May: 175 individuals
1st June: 138 - after which I expected the spike in numbers to gradually regress back to the mean
2nd June: 382
3rd June: 437
4th June: 1740
5th June: 411
6th June: 360

To place this in some form of perspective, I had recorded a total of 881 Diamond-backs during the previous ten years. This was by no means a high number compared with many other coastal stations, but it is the number which I had recorded at home in Newhaven, and that figure is therefore a useful datum for comparison. In five nights from 30th May that total was comprehensively eclipsed and I recorded 1152 individuals; this total was itself eclipsed on the night of 4th, bringing the total in six nights to 2892! This total did not include the few hundred Diamond-backs seen resting and possibly nectaring on a flowering Cordyline in my front garden on 2nd June; it did not include the 2000+ individuals (a conservative estimate) which I saw on the evening of 3rd while walking from home over the apex of the Downs along the east of the Ouse Valley to Bishopstone - a distance of just over one mile as the crow flies; it did not include many hundreds more seen on 4th along a well-known spot for migrants on the Downs above Denton and Poverty Bottom. It was at this latter location that the scale of this invasion occurred to me. How does one count a tiny micro-moth flitting about here there and everywhere in such great numbers that, for every one seen, another ten - another thousand? - pass unseen? Add to this a carpet of buttercups which spread before me across 45-odd acres in a lurid nebula and the task appeared even less attainable. Counting the buttercups would have been less of a challenge. I gave up. I simply enjoyed the spectacle before me.

Diamond-back Moth Plutella xylostella

So what is the Diamond-back Moth? It is a member of the Plutellidae family of moths. There are seven species found within the UK, but only three of these are found in the south east and all of these have been recorded at Newhaven: the Diamond-back, the common Grey-streaked Smudge (Plutella porrectella) and less common Bittercress Smudge (Eidophasia messingiella). Each of these species feeds on plants of the cabbage family. The Diamond-back is a small species: about 8mm in length at rest. It is a neat-looking insect, with a long-thin body around which the wings are folded roof-like when at rest. It has an alert upright resting posture and its antennae are forward pointing, much like its migratory attitude. This moth is a visitor from the continent each year and it is seen in variable numbers from one year to the next. In observing the flight of this species, it is a remarkable thought that they make it across any stretch of water, but this they do, presumably at high altitude, before making landfall in the UK.

Being based on the south coast at Newhaven and only about seventy miles from continental Europe (the French coast between Fecamp and Dieppe is nearest), migrant insect species are both a staple of life every year for the Lepidopterist and a fascinating area of study. The Ouse Valley and Downs to the east are a fairly reputable station for migrant sightings. The Willowherb Hawk-moth (Prosperpinus prosperpina) Oleander Hawk-moth (Daphnis nerii) sightings of 1985 and 2014 respectively are probably the best examples, but getting on for forty migratory moth species have been recorded in Newhaven during the past ten years and these have included occasional sightings of Crimson Speckled (Utetheisa pulchella), regular small numbers of Olive-tree Pearl (Palpita vitrealis), Vestal (Rhodometra sacraria), Gem (Nycterosea obstipata), Ni Moth (Trichoplusia ni), and very good numbers annually of Bloxworth Snout (Hypena obsitalis), which, along with several other migrant species, has begun to colonise along the coastline. Silver Y (Autographa gamma), Red Admiral (Vanessa atalanta) and Diamond-back are the most commonly encountered on a yearly basis, but migrant species are well known for their episodic spikes in abundance during specific continental immigration events. One famous recent example was seen in 2008 when many millions of Painted Lady (Vanessa cardui) butterflies migrated northwards from the Atlas Mountains of North Africa as far as the Arctic, the generations leap-frogging each other as they progressed. 

Most of these and the other migratory species are seen during periods of strong winds from the south, but immigration events occasionally occur from other directions and the current Diamond-back invasion appears to be one such example of an immigration from the east or north east. The spike in Diamond-back numbers which began during the final two days of May appears to be the greatest immigration event by that species and it might yet prove to be amongst the most significant of migratory episodes observed during the past 170 years, when formal recording began. Bearing in mind that these moths will breed following their arrival, we could be in store for a second bonanza later in the summer.

Diamond-back Moth at Castle Hill LNR, Newhaven