Some of the insects of
Shetland have been reasonably well-studied, especially the moths which
were the subject of much attention at the end of the 19th century when it
was discovered that there were many unusual melanic (dark) forms in the
islands. As well as several subspecies or varieties of moths there is a
semi-endemic species of weevil of dubious taxonomy and an semi-endemic
subspecies of bumblebee. The blackfly
Simulium zetlandense
was named for science based on a specimen from Shetland but is now known
to occur in Fennoscandia.
Moths
There are five named
subspecies of moths which appear to be good Shetland endemics i.e.
they are not found anywhere else in the world and all (or nearly
all) of the the individuals in Shetland conform to the characteristics of
the named subspecies.
Eupoecilia angustana thuleana A small
tortrid
micro-moth which is common in grassy areas on Unst, Yell
and Mainland and which flies in June and July It was
originally described as a new species. It is much more heavily marked than
the nominate subspecies which is found in the rest of Britain.
Red Carpet
Xanthorhoe decoloraria hethlandica. A common
geometrid moth found throughout the islands, usually recorded at light at
night from June to October, but mainly
in July and August. The Shetland race is orange-brown in colour and not
white and dull red like the subspecies found in the rest of Britain.
Photo
by Dave Hall.
Silver-ground Carpet
Xanthorhoe montanata shetlandica A
common geometrid moth found throughout the islands, sometimes found flying
by day, but most often recorded at light at night. It is particularly
common in the northern isles of Shetland. It flies from June to August.
The Shetland race is slightly smaller
than the Mainland race, usually with a less distinct bar.
Photo by Micky Maher.
Netted Pug
Eupithecia venosata
fumosae A locally frequent
moth, found in the vicinity of beaches throughout the islands, wherever
the foodplant Sea Campion Silene maritima is found. It flies in May
and June but is rarely seen unless traps are run close to beaches,
although larvae (caterpillars) are easily found by examining Sea Campion
seed pods. The Shetland subspecies is darker than the form on the British
Mainland. It is probably endemic to Shetland but moths resembling this
race are occasionally found in Orkney.
Photo
by Micky Maher.
Grass Rivulet
Perizoma albulata subfasciaria A locally common
but probably declining geometrid moth found throughout the islands, except Fair Isle.
It is usually seen by day around the food plant Yellow Rattle
Rhinanthus minor
and is seen from June to August. The Shetland race is smaller and darker
than the race found in the rest of Britain.
Photos by Steve Minton.
Four more named
subspecies appear to form at least the majority of the Shetland
population, but are also found elsewhere. It may be that populations
elsewhere are best regarded as belonging to different subspecies. This is
because it is likely
that the taxon (in this case subspecies) present in Shetland would be
paraphyletic - in other words, the populations have different origins and
do not share a common ancestor which separate them from other races.
Modern taxonomics would make this treatment untenable and, if that is the
case, then they should be treated as separate races.
Ghost Moth
Hepialus humuli
thulensis A common moth found throughout the
islands, except Fair Isle. Most males are dark, sometimes exceptionally so, although pale specimens also
occur. The species flies from May to August, but mainly July, and it may
often be seen flying at dusk in the 'simmer-dim' (summer nights). Larvae
(caterpillars) feed on roots, possibly for up to two years, and are
frequently dug up in gardens. The moths found in the Faroe Islands are
also included in thulensis and, in this case, it is possible that
Faroe was colonised via Shetland, in which case common ancestry is
possible.
Photos
by Steve Minton, Roger Riddington.
Yellow Shell
Camptogramma bilineata atlantica A frequent,
but very local, moth found on on Mainland, Muckle Roe, Fair Isle and Unst.
It flies from June to August and may be seen by day or attracted to light.
The race atlantica , which is darker and duller yellow than the
Mainland British form, is also said to occur in the Outer Hebrides, but it
seems unlikely that these two populations share a common ancestor.
Dark Marbled Carpet
Chloroclysta citrata pythonissata A locally
frequent moth throughout the islands, except Fair Isle. It may be seen by
day or at light from July to September but mainly in August. The Shetland
race is also found in Orkney and, as Shetland was probably colonised via
Orkney, common ancestry is likely.
Photo by
George Petrie.
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The Exile
Apamea zeta [exulis?] A locally common on
moorland on Mainland, Muckle Roe and Unst; one undated record from Yell
and an unconfirmed record from Fair Isle. It flies in July and early
August and is attracted to light or sugar. It was originally thought to be endemic
species, Apamea exulis, but it was then regarded as being
part of a widespread species which includes the Northern Arches Apamea
zeta assimilis, which is found in northern Scotland. Most recently,
the Shetland population has lost its status as an endemic subspecies and
has been treated as the only British population of the widespread Scandinavian
subspecies A. z. marmorata. Some authorities, including Dr Svend
Kaaber who has seen the species in Denmark, Faroe and Shetland, still
believe that the Shetland population deserves subspecific status.
Photo by Wendy Dickson.
Five
more
species have named forms which are only found in Shetland (two currently
recognised as subspecies), but as these are often found alongside typical
individuals and they often only form a small proportion of the population,
they can be regarded as no more than forms or varieties. There are, in
fact, some other forms which are arguably as distinct as some of these
named forms, but none have official names.
Map-winged Swift
Hepialus fusconebulosa f. zetlandicus A common moth found
throughout the islands, often seen flying at dusk or attracted to light,
mainly in June in July but recorded from May to August. The Shetland form,
which is bright and variegated, only forms a
small proportion of the population and is one of three forms found in the
islands.
Photo
by Mike Pennington.
Garden Carpet
Xanthorhoe fluctuata f. thules A frequent moth
throughout the islands and the only Shetland macromoth with a regular
second brood. Consequently it can be found from April to September. The
Shetland form is a dark melanic but a melanic form is also found in towns
and cities on Mainland Britain and it only forms a small proportion of
the population in Shetland.
Twin-spot Carpet
Perizoma didymata [hethlandica?] A locally
common but declining moth found throughout the islands and flying from
July to September. Although still accepted as a named subspecies, browner
and duller than the Mainland British race, moths of this form only seem to
constitute a small proportion of the Shetland population, so the race is
not really valid.
Photo by Rob Fray.
Autumnal Rustic
Eugnorisma glareosa f. edda A common
throughout the islands, usually found at light and recorded in August and
September. The dark form edda is also occasionally found outside
Shetland but it is commonest in the islands where it increases from less
than 5% of the population in the south Mainland to over 95% on Unst.
Photo by Mike Pennington.
Ingrailed Clay Diarsia mendica [thulei?]
An abundant moth found
throughout the islands, from June to October but mainly in July and early
August. A highly variable species, moths conforming to the description of
the Shetland subspecies form only a tiny part of the population, so the
race is not valid. .
Beetles
a species of weevil
Protapion ryei
(=
Apion reyi
)
A tiny weevil which feeds on the
flowerheads of
Red Clover Trifolium pratense.
It was formerly thought to endemic to Shetland but is now believed to be
present in Orkney and the Inner and Outer Hebrides. It may not be a valid
species but the extreme end of a cline (a gradual change over a long
distance) and therefore part of the species Protapion assimile, a
common species throughout Britain.
Bumblebees
Small
Heath Bumblebee
Bombus jonellus
vogti Scarce on moorland on Mainland, Muckle Roe and Unst at least,
flying from April to September. The race breeding in Shetland has a yellow
tip to the abdomen, rather than the white tip found in most other races.
Photos by Mike Pennington.
Shetland
Bumblebee Bombus muscorum
agricolae
Very common throughout the islands, flying from April to October. It is
much more colourful than its mainland British counterpart (which is known
as Moss Carder Bee), with a bright orange thorax and a yellow abdomen. It
is also said to occur in
the Outer Hebrides, but it seems unlikely that these two populations share
a common ancestor, so it may be best to separate the populations as
different subspecies under the rules of paraphyly.
Photo
by Hugh Harrop.
Nature in Shetland
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