Download The Earwig species of Devon and Cornwall

The Earwig species of Devon and Cornwall
by Malcolm Lee, Gullrock, Port Gaverne, Port Isaac, Cornwall. PL29 3SQ [email protected]
Some readers may be unaware that there are more than one species of earwig. Of those who are aware,
only a handful will have seen any other than our Common Earwig Forficula auricularia. In fact, both
counties have three confirmed native species, and there is recent tantalising evidence of a fourth species,
for which there has been no definite UK record for 70 years. Apart from the Common Earwig, we have its
close relative Lesne’s Earwig Forficula lesnei, and the Lesser Earwig Labia minor (see Fig 1). The
possible fourth species is the Giant or Tawny Earwig Labidura riparia. Also recorded here is an adventive
species, the Ring-legged Earwig Euborellia annulipes, which can become established in heated premises.
Fig 1: Native earwig males showing relative sizes.
Common (left), Lesne’s (centre) and Lesser (right)
All earwigs are under-recorded. This applies even to the Common Earwig, as shown in the distribution
map at Fig. 2 left. A concerted effort last autumn filled in all the Cornish 10km squares, but thirty squares
in Devon have never had any sightings, the most under-recorded county in southern England. This species
should be virtually everywhere, so any records for those blank squares would be much appreciated.
Fig 2: Recorded distribution of Common Earwig (left) and Lesne’s Earwig (right) (10km resolution)
Common Earwig Forficula auricularia Linnaeus: This most familiar insect needs little introduction. It
has fully developed hind wings, intricately fan-folded under the elytra (modified fore wings), but very
rarely uses them. Indeed, many have doubted that it ever flies. One of the very few authoritative first hand
reports of flight is from the Plymouth entomologist C. W. Bracken, whose 1916 Devon Orthoptera paper
states ‘I have taken it making short flights over flowers in the evening’.
It is found throughout the UK, right up to the far north of the Shetland Isles, in almost any habitat, indoors
or outdoors, only becoming less frequent in very dry locations like short grass and dry heath.
Lesne’s Earwig Forficula lesnei Finot (Nationally Scarce B): This is smaller than the Common Earwig,
around 6-8mm long, and lighter in colour. It is completely wingless. Males are easiest to identify, the key
points being shown in Fig 3.
In the UK, Lesne’s Earwig is right at the northern edge of its range, with scattered localities in southern
Britain up to north west Cambridgeshire. It does not appear to have specific habitat requirements, being
found outdoors in rough vegetation, with a preference for basic soils.
The earliest records from our counties were by the Dorset entomologist C. W. Dale in the 1890s, when he
found it at Sidmouth and on the Isles of Scilly. The Scillonian colonies were re-found by Chris Timmins in
autumn 1993, when he also found it on mainland Cornwall at Marazion. It has now been found in
Cornwall at a handful of locations, and in Devon at a few coastal localities east of Start Point. Whilst the
records suggest a maritime distribution, this may not be so. In adjacent Somerset, there are many records
well away from the coast, and more searching may reveal inland colonies in Devon and Cornwall.
Fig 3: Common (left) and Lesne’s (right)
Key differences in males (Size, A, and B also apply to females)
Size: Lesne’s about two thirds length of Common
A: Common – wings protrude from elytra.
Lesne’s – no wings to protrude
B: Common – Straight sided abdomen
Lesne’s – ‘Barrel’ shaped abdomen
C: Common – Basal plate less than a third of pincers
Lesne’s –Basal plate about half of pincers
Lesser Earwig Labia minor (Linnaeus): Our tiniest earwig, just 4mm long, and not much larger than an
ant. It may be confused with a small staphylinid beetle, but the presence of pincers confirms you are
looking at this species. The Lesser Earwig is fully winged, and will fly very readily in sunshine.
Fig 4: Lesser Earwig
This earwig needs the warmth provided by decaying compost and dung heaps, outside of which it cannot
normally survive for long. Within those warmth enhanced habitats, the Lesser Earwig is found throughout
Britain, with records as far up as north east Scotland.
A century ago, when almost every farmyard would have had a mature dung heap, this earwig was
undoubtedly abundant. With the change to liquid slurry tanks, it is probably much less common now.
However, it may still be found around horse riding stables, and will also utilise garden compost bins.
When it flies on warm evenings it can be attracted to light, so moth recorders may be the first to observe its
presence in a locality. Fig 5 gives the Devon and Cornwall distribution of all records.
Fig 5: Recorded distribution of Lesser Earwig (10km resolution)
Giant or Tawny Earwig Labidura riparia (Pallas): There has been no definite UK record for this earwig
since the 1930s. It is nearly twice as long as the Common Earwig, yellowish-brown in colour, and has
long, straight, pincers (Fig 6). Historically it was confirmed from just two UK locations; Folkestone in
Kent during the 1870s, and at Pokesdown, near Bournemouth (SZ12-91-) until the early 1930s.
Unconfirmed pre-war records exist for Dorset and the Isle of Wight.
Fig 6: Giant Earwig (picture Petr Kocarek)
Whilst there is no definite evidence in the form of a photograph or specimen, the only UK reports of the
Giant Earwig since those pre-war days are all within our counties. In 1982 a sighting was made at the top
of Coxes Cliff SSSI, west of Branscombe (SY18-88-), but was not followed up at the time. On 28th April
2004, around 5am, a Devon ecologist was sitting just above the high water mark by the tidal debris on the
bank of the River Camel east of Wadebridge (SX00-71-), when he noticed a large earwig on his trousers.
Apart from its large size (c. 3cm long), he was struck by its tawny colour and the straight pincers.
Unfortunately, the specimen was not collected. It was only two weeks later, after checking his reference
books, that the recorder appreciated what he saw and contacted the Cornwall Wildlife Trust. Following
publication of details of this record in British Wildlife, Andrew Duff reported that an earwig he found
under a stone near Lizard Point (SW69-11-) on 19th June 1991 exactly matched the photograph in the
article, and considered it was this species, but no photograph was taken or specimen collected.
The two Cornish locations have been checked out with negative results so far. Checking under stones
around the Coxes Cliff area may prove successful. The Giant Earwig is nocturnal and lives in burrows, so
it could remain undetected by casual daytime searches. Night-time might be more fruitful, but the slippery
muddy bank of a tidal river has too many obvious dangers, as does a night-time search on clifftops.
Ring-legged Earwig Euborellia annulipes (Lucas): The first UK record for this adventive species was in
1894 at a bakehouse in Market Street, Tavistock, where it had been breeding for some 20 years. Bracken
gave the story of how these insects arrived at a quiet inland Devon town. It seems that they were brought in
on the luggage of the previous owner’s son-in-law, a Jamaican merchant, when he came to visit. There is a
second historic record when two specimens were taken on 17th June 1900 near Falmouth Railway Station
and Docks in Cornwall. Presumably they had arrived on an inbound ship.
Fig 7: Ring-legged Earwig
This cosmopolitan species originates from the Mediterranean area, but is now widely distributed
throughout the world in warmer areas, and indoors in cooler climates. It is a blackish-brown, flightless,
earwig with yellow legs marked with dark bands (Fig 7) from which it gets its common name. The most
recent record is of a thriving population in the Humid Tropic Biome of the Eden Project near St. Austell
(SX04-54-), when they were found amongst leaf litter in autumn 2002. In Smithers, Trodd & Lane 2003,
they were recorded as the similar Bone-house Earwig Marava arachidis (Yertsin), but a subsequent review
by Peter Smithers confirmed it was the Ring-legged Earwig.
Searching for native earwigs
During the day, earwigs like to hide in crevices and other hard to access places, so are not readily seen by
casual searching. The following method, recommended by Chris Timmins, is an easy way of finding both
Common and Lesne’s Earwig in the field, and can be undertaken right through to late autumn and even
into winter, when outdoor insect recording is usually impossible. Simply look for the dead stems of
Hogweed Heracleum sphondylium, which are usually abundant. If you pull up the hollow stems and start
to split them, any sheltering earwigs will tumble out, often in quite large numbers. It helps to have a pot
underneath to catch the fast moving insects. The instant check for which species you have found is to look
for the protruding wing tips at the back of the elytra. If they are visible, it is the Common Earwig. If not, it
could be an immature Common Earwig nymph, or Lesne’s Earwig, so check with Fig 3. I would be happy
to look at any specimens about which you are unsure.
For the Lesser Earwig, checking any small flying insect around garden compost bins or heaps on a hot
summer’s day is a good place to start. David Baldock gives this tip, told to him by John Widgery the
former National Orthoptera Recorder ‘The best method of finding it is to dig about 6 inches into the (dung)
heap where it is moist and warm. The earwig is very active and will probably dive into the manure as soon
as it is exposed. Remember that it is very small and as soon as you see it dive, grab the manure and put it
on a sheet of white cloth or paper and wait for it to crawl out.’ Getting close up and personal with dung
heaps seems above and beyond the call of duty, so stick to compost heaps!
If you come across any earwig species, I would welcome details to ensure they are fed into the national
Orthoptera Recording Scheme.
Malcolm Lee
REFERENCES
Baldock D. W., 1999 Grasshoppers and Crickets of Surrey. Surrey Wildlife Trust, Woking. 111pp
Bracken C. W., 1916 The Orthoptera of Devon Transactions of the Devonshire Association for the Advancement of Science,
Literature and Art. 1916. xlviii. pp. 267-282
Haes E. C. M., 2004 Orthopteroid Insects in Cornwall and the Isles of Scilly: an updated provisional atlas Environmental Records
Centre for Cornwall & Isles of Scilly, Truro. 68pp.
NBN Gateway, 2004 Interactive Species Distribution Maps for Devon using Orthoptera Recording Scheme database. via
http://www.searchnbn.net/index_homepage/index.jsp
Smithers, P., Trodd, C., & Lane, E., 2003. Ground Dwelling Invertebrates in The Humid Tropic Biome at the Eden Project. Bulletin
of the Devon Invertebrate Forum 10 November 2003. pp3-5
Sutton P. G., 2004a: Classic Entomological sites: Branscombe Beach and Undercliff, East Devon. Bulletin of the Amateur
Entomologists’ Society 63 (No. 453 April 2004) pp. 47-67
Sutton P. G., 2004b: Wildlife Reports; Grasshopper and relatives. British Wildlife 15 (No. 5 June 2004) pp358-9