Overview of Moths
in Shetland
Moths
are the members of the order Lepidoptera. they are close relatives of
butterflies - indeed there is not really any scientific distinction
between the two. In Shetland almost 300 species of Lepidoptera have been
recorded so far. Species are being added to this list at regular intervals
thanks to the activities of the Shetland Entomological Group. This page
gives a brief overview of moths in the islands.
Below are the names of the
major groupings of moths.
-
Swifts ... including the endemic Shetland Ghost Moth
-
miscellaneous Microlepidoptera ... some of the smaller and more
inconspicuous moths
-
Tortrids ... another group of Microlepidoptera
-
Pyralids ... more of the smaller moths, including the grass moths
-
Geometers ... Carpets, Pugs and allies
-
Hawkmoths ... some of the largest and most spectacular of the moths
-
Tigers and Lymantrids ... a small but colourful group
-
Noctuids ... the largest group of moths, including most of the larger
species
Photo
above: Beautiful Golden Y Autographa pulchrina
Swifts Hepialidae
Only two species from this group are found in Shetland. They are both
common species - the Map-winged Swift Hepialus fusconebulosa and
the Ghost Moth Hepialus humuli. The Ghost Moth gets it's name from
the white appearance of the male - however, in Shetland the male is yellow
like the female, presumably because white males would be too obvious in
the light Shetland nights. Because of their appearance Shetland Ghost
Moths are
separated as a subspecies - H. h. thulensis.
The
caterpillars of the swifts feed on roots and they probably take two years
to become adults. Like several moths, the adults do not feed.
photos: left, Map-winged Swift Hepialus fusconebulosus and right, a
male Shetland Ghost Moth Hepialus humuli thulensis
miscellaneous Microlepidoptera
The microlepidoptera form more than half of the moths found in Britain and
they also include the next two groups, the Tortrids and the Pyralids.
These latter groups are comparatively well-studied, however, whereas most
of the rest of the micros are very much the realm of the specialist. Many
species are hard to find as adults and few are more than 15mm long. Some
have larvae which feed inside leaves or stems, hence they are known as
leaf-miners.
Some
of the more obvious members of this group are the Housemoths, present in
most houses throughout Shetland. The smaller White-shouldered Housemoth
Endrosis sarcitrella is the commoner of the two. The other species is
the Brown Housemoth Hofmannophila pseudospretella, originally a
colonist from South America.
The
commonest of the resident species is the tiny Nettle-tap Anthophila
fabriciana. The caterpillars of this species feed on nettle and the
adults can be seen flying around clumps of the foodplant anywhere in the
islands from mid July into August.
Not
many of the smaller moths are migrants, but the Diamondback Moth
Plutella xylostella is one of the most famous of all migrant moths. It
occurs in Shetland every year, but in variable numbers. Occasionally,
there are huge influxes of thousands of moths, as in early July 1994. The
moth is unpopular as it is a pest of Brassica crops such as
cabbage. In Shetland the garden plant Sweet Rocket Hesperis is also
frequently used as a foodplant.
photo:
Nettle-tap Anthophila fabriciana on it's foodplant, nettle
Tortrids
This
is another group of small moths, rarely longer than 15mm. Almost 40
species have been recorded in Shetland, almost all of which are resident.
Many
species are active by day, but they are easily overlooked because of their
small size. Eana osseana is one of the commonest moths in Shetland.
Along with one of the Pyralid moths it is the small moth kicked up from
grassy areas throughout the islands, although it flies later and is
commoner in August.
Some
of the other common day-flying totrids include Syndemis musculana ,
found on moorland in June, Olethreutes lacunana which is another
moorland species commonest in July, Bactra lancealana found in any
damp, rushy areas in the summer. Eupoecilia angustana and Cydia
succedana are both common around Birdsfoot Trefoil on Unst, but appear
to scarcer elsewhere.
Other
Tortrids are active by night, including the relatively large, grey Eana
penziana and several species of Acleris, the commonest of which
is the orange-brown Acleris aspersana.
Pyralids
These
are the largest of the micromoths, some with wingspans of several
centimetres. About 20 species have been recorded in Shetland, eight of
which are migrants.
The
commonest Pyralid, and probably the commonest moth in Shetland, is the
grassmoth Agriphila straminella which can be extremely abundant in
grassy areas in July. Another common and obvious species is Udea
lutealis, a cream-coloured, Concorde-shaped species which is common in
August. Eudonia angustea , a slender species, can be quite common
at lighted windows in August.
Two
other resident species are upland species in the rest of Britain.
Eudonia alpina is found to sea-level in Shetland but is very scarce at
low-level elsewhere in Britain. The distinctive orange-brown Catoptria
furcatellus is very scarce anywhere in Britain and is only found in
Shetland on the highest hill, Ronas Hill.
The
commonest migrant is Rush Veneer Nomophila noctuella, recorded
almost annually in variable numbers. The noted migrant Rusty-dot Pearl
Udea ferrugalis has also turned up in the last couple of years. Other
migrants are all very rare, including the only Scottish record of Thistle
Ermine Myelois cribrella on Fair Isle in 1991, and one of a handful
of Scottish records of Numonia advenella.
Geometers
This is a large group of moths, most of which rest with their wings either
out flat or held together vertically over their back, rather like a
butterfly. Several species are active by day. The larvae are also active
by day and so are easily found. The caterpillars move with in
characteristic fashion, as though they are measuring, leading to the
popular name of "inchworm".
The two commonest geometers in Shetland are both represented by distinct
Shetland subspecies - the Red Carpet Xanthorhoe munitata hethlandica
(illustrated on the
Shetland Entomological Group
home page) and the Silver-ground Carpet Xanthorhoe montanata
shetlandica (illustrated above). The Red Carpet is very common in
South Mainland but the Silver-ground Carpet appears to be commoner in the
Northern Isles. It can often be found by day, often on moorland.
Another very common species is the Winter Moth Operophtera brumata
. It is the only species to fly in mid-winter in Shetland, and it can be
very common on mild December nights. The female of this species is
flightless but caterpillars have been known to spread by "ballooning" -
getting carried on air currents on silk spinnings in the same way as
spiders. The green larvae are common on trees and heather in summer, and
they can be a significant pest. Another pest of trees, usually willows, is
the July Highflier Hydriomena furcata. It flies in August in
Shetland, incidentally!
There are several other common resident species. On the hills and moorland
the Chevron Eulithis testata and the Northern Spinach Eulithis
populata are both common, as is the tiny Satyr Pug Eupithecia
satyrata . The Netted Pug Eupithecia venosata is common around
suitable beaches. Around crofting land the Garden Carpet Xanthorhoe
fluctuata , the Grass Rivulet Perizoma albulata and the
Twin-spot Carpet Perizoma didymata are all common. Many of these
species occur in local forms (not always comprising the entire population.
This is probably because Geometers are not famous migrants so the isolated
populations in Shetland have developed their own characters.
One
or two Geometers do migrate and have turned up in Shetland. these include
the Gem Orthanoma obstipata , a well-known long distance migrant,
and species such as Bordered White Bupalus piniaria and the Magpie
Moth Abraxas grossulariata which have probably just wandered from
the established populations on the British Mainland.
photos: left to right - Magpie Moth Abraxas grossulariata, Chevron
Eulithis testata (top right) and Garden Carpet
Xanthorhoe fluctuata
Hawkmoths
These
are some of the largest moths in Britain and many species are strong
flyers and long distance migrants. In Shetland the commonest species is
the Convolvulus Hawkmoth Agrius convolvuli which is recorded
annually in small numbers. The Bedstraw Hawkmoth Hyles gallii , the
Hummingbird Hawkmoth Macroglossum stellaturum and the Death's Head
Hawkmoth Acherontia atropos have all been recorded in the islands,
each on fewer than 20 occasions. The Privet Hawkmoth Sphinx ligustri
and the Striped Hawkmoth Hyles lineata have only been recorded
once each.
photo: Hummingbird Hawkmoth Macroglossum stellaturum
Tigers and
Lymantrids
Only
one species in this group is resident in the islands - the inaccurately
named Wood Tiger Parasemia plantaginis is reasonably widespread on
moorland on Mainland and Foula. The Garden Tiger Arctia caja has
occurred once as a vagrant and singles records of the Lymantrids White
Satin Moth Leucoma salicis and the Vapourer Orygia antiqua
presumably also refer to wandering or vagrant individuals.
Noctuids
The
Noctuids are a huge group of moths which includes some very common
resident species as well as some prominent migrants.
The
commonest noctuid moths in Shetland are the Hebrew Character Orthosia
gothica which flies in April, the Shears Hada plebeja which
flies in May to June, the Clouded-bordered Brindle Apamea crenata
which flies in June to July, the Dark Arches Apamea monoglypha
which flies in July to August and the Antler Cerapteryx graminis
which flies a little later in the same months.
Some
nationally rare moths are resident in Shetland. The Exile Apamea zeta
marmorata was originally described as a new species to science, but is
now placed with the Scandinavian subspecies of a widespread sub-polar
species. The Northern Dart
and the Broad-bordered White Underwing Anarta
melanopa were both apparently common last century, but are rare now.
In
the autumn there are several fairly common moths including the Autumnal
Rustic Paradiarsia glareosa, the Square-spot Rustic Xestia
xanthographa and the Brindled Ochre Dasypolia templi. Other
common moths in autumn, such as the Brick Agrochola circellaris,
the Satellite Eupsilia transversa and the Angle Shades
Phlogophora meticulosa are probably short-distance migrants from
Britain or the near Continent.
Several long-distance migrants are common in Shetland, most obviously the
Silver Y Autographa gamma, which turned up in tens, if not hundreds
of of millions in August 1996.
The
Dark Sword Grass Agrotis ipsilon, is another annual long-distance
migrant but Shetland is also a very good place for rarer migrants from
Scandinavia. There is no better place in Britain to see migrant Great
Brocades Eurois occulta, from Scandinavia.
Even
rarer moths also turn up with national rarities such as the Clifden Non-pareil
Catocala fraxini or the Scarce Bordered Straw Heliothis armigera.
In 1996 two extreme rarities were recorded - Dewick's Plusia
Macdunnoughia confusa with fewer than 30 British records and the
seventh and eight British records of Scarce Brindle Apamea lateritia.
photos: top to bottom - Silver Y Autographa gamma, Square Spot
Rustic Xestia xanthographa, Satellite Eupsilia transversa, and
Dark Arches Apamea monoglypha
Nature in Shetland
