Butterflies of
Britain & Europe
Silver-spotted
Skipper
Hesperia comma
LINNAEUS, 1758
Family - HESPERIIDAE
subfamily -
HESPERIINAE
introduction
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habitats |
lifecycle |
adult behaviour
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Silver-spotted Skipper
Hesperia comma, male, Stockbridge
Down, Hampshire |
Introduction
The
Silver-spotted Skipper is widely distributed in Europe, but absent from northern
Britain, lowland areas of Spain and Portugal, southern Italy, the Mediterranean
islands, and the Balkans. Beyond Europe it occurs in the Atlas mountains of
Morocco, and across Asia to Amurland. It is also found over mush of Canada and the western USA, where it is known as the Holarctic Grass
Skipper.
The
upperside pattern is typical of Hesperiines throughout the world, but in Europe
it cannot be confused with any other species except the Large Skipper Ochlodes venata,
which is more brightly marked above, and lacks the distinctive silver
spots on the underside hindwings of
comma.
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Silver-spotted Skipper
Hesperia comma, Hampshire |
Habitats
In Europe this butterfly
can be found in a very wide range of grassy habitats, and even occurs high on
limestone mountains at altitudes of up to 2300m.
In Britain the butterfly
was formerly found across most of southern and central England. Its range
contracted severely during the 20th century, largely due to the
elimination of it's larval foodplant sheep's fescue grass from many former
sites as a result of agricultural improvement, afforestation, and urbanisation.
The spread of myxomatosis, which greatly reduced the populations of rabbits
during the latter half of the 20th century also resulted in a mass of local
extinctions, as sites on deeper soils quickly became overgrown with rank
grasses. Since about 2002 the rabbit population has recovered and grassland
sites across southern England have become more heavily grazed to the point where
they have once again become suitable for this species. Unfortunately while the
Silver-spotted Skipper is reappearing, the heavy grazing has been detrimental to
certain other species such as Dark Green Fritillary and Marbled White.
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Silver-spotted Skipper
Hesperia comma, male, Stockbridge
Down, Hampshire |
At it's sites in southern
Britain the species is restricted to well drained and thinly soiled calcareous
grasslands where sheep's fescue grass grows sparsely. Extensive areas of bare
ground are a vital element - Silver-spotted Skipper sites are typified by the
sward being pock-marked with myriads of small bare patches exposed by rabbit
excavations.
At most sites the
populations are restricted to a limited area, typically on the upper slopes of
south or east facing hillsides. However, at sites which are particularly exposed
to the wind, or at higher altitudes, the populations tend to be limited to
sheltered areas at the base of hills.
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Silver-spotted Skipper
Hesperia comma, male, Stockbridge
Down, Hampshire |
Lifecycle
In Europe and most of North
America the butterfly is single-brooded, but in Alaska the
lifecycle takes 2 years to complete - the first winter spent as
an egg, and the second as a fully grown larva or pupa. In the hotter parts of the Mediterranean the species
over-winters as a fully grown larva, amongst grass roots. In the
UK the species always over-winters in the egg stage.
In Britain the butterflies emerge in
mid-late
July, and have a short flight period - no more than 2 or 3
weeks. At higher altitude sites such as Old Winchester Hill in
Hampshire, the emergence time is generally about a week later
than elsewhere.
Published material by Thomas states that females seeking egg-laying sites habitually
settle in rabbit scrapes or on other small patches of bare
ground, and then hop and walk until they locate a tiny tuft of
sheep's fescue grass, nearly always choosing plants that abut
onto bare ground. My experience is that this is often not the
case - most of the females which I have followed at Old
Winchester Hill and at Broughton Down dart about over short
fescue sward and land randomly, usually well away from rabbit
scrapes or other bare ground. They then thrust their abdomen
forward and lay a single egg on a grass blade, without any
investigative hopping or walking about. After ovipositing they
usually remain on the spot for a minute or so before flying a
metre or two to another similar spot where they repeat the
process. It seems likely therefore that egg-laying behaviour
varies from site to site depending on local habitat and climatic
conditions.
The straw-coloured eggs are laid singly, on the narrow leaf blades of sheep's fescue grass Festuca ovina.
Suitable plants are often revisited by the same female several
times, or used by several different females, and it is possible
to find up to a dozen eggs placed very close together, but all
laid on separate occasions.
The larvae are fully developed
within the eggs by early autumn, but do not hatch until the
following March. They feed nocturnally on the fine tender leaf
blades, sheltering by day in a flimsy silken tent spun at the
base of a grass tuft. When fully grown they are dark green,
with a black head, and very wrinkled in appearance.
The chrysalis has a dark brown
abdomen, and blackish wing cases and head. It is formed within a
cocoon of coarse silk,
at the base of grass tufts. The butterfly
develops very quickly, emerging after only about 7 days.
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Silver-spotted Skipper
Hesperia comma, male, Stockbridge
Down, Hampshire |
Adult behaviour
Silver-spotted Skippers
only fly on warm sunny days. They are then extremely active, with
a very rapid flight, zipping and darting about in every direction
just above the surface of the ground. As soon as cloud obscures
the sun they settle, and often bask in rabbit scrapes, hoof prints, or on
the leaves of sprawling bramble growth.
When conditions become too cool for flight they rest temporarily
in tussocks of grass that abut onto bare ground, or settle on low
foliage ( the male illustrated below for example was found on a
tiny field maple sapling ). At such times they become extremely
torpid. Overnight, they shelter in small
bushes or amongst patches of dense foliage.
Both sexes nectar
avidly at low growing flowers including stemless thistle,
carline thistle, eyebright, stonecrop, bird's foot trefoil, self
heal, small
scabious, lady's bedstraw, hawkbit, devil's bit
scabious, red clover and
autumn gentian. Their favourite nectar source however is wild basil -
as illustrated by the activities of a male which I watched in August 2007 at Broughton Down.
The butterfly visited 17 different wild basil plants
in quick succession, completely ignoring all other flower
species. After about 4 minutes I lost track of the butterfly when
it got into a dog-fight with another male, but I continued to
watch various other males that afternoon, and all showed a very
strong preference for wild basil, despite a profusion of other
nectar sources.
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Silver-spotted Skipper
Hesperia comma, male, Broughton
Down, Hampshire |
Males occupy
loosely defined overlapping territories, where they fly
continuously from flower to flower, stopping periodically to bask
on patches of bare ground, or on low herbage. They fly up
instantly to intercept and investigate almost any small, rapidly
flying insect, including flies, small bees, moths and other
butterflies. They are very pugnacious in nature, and will chase
off even the largest and most powerful butterflies, including
Painted ladies and Dark Green Fritillaries, but rather oddly elect
to ignore Burnet moths and Silver-Ys !
During male /
male encounters, the butterflies zigzag rapidly, close to the
ground, and then spiral upwards in tight circles until the weaker
male is ousted, whereupon the other male returns to within a few
metres of it's original position.
When
a virgin female is encountered she is abruptly forced to land on the ground, usually in a
tuft of grass, where she vibrates her wings rapidly. The male
lands alongside her, and buzzes excitedly around her, showering
her with pheromones from his androconial scales. The female then
flies in a series of short hops, until she finds a comfortable
spot to settle, and the male then settles by her side, curving his
abdomen round until he engages her. He then slowly turns to face
away from her, after which the pair remain stationary in
copulation for about 2 hours.
When a gravid female is encountered the same courtship ritual is
followed, but after settling together 3 or 4 times in succession
without successfully copulating the male flies off. There does not
appear to be any visual rejection signal given to the unwanted
male, so presumably mating only takes place of the female is
receptive to the male pheromones.
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Silver-spotted Skipper
Hesperia comma, female, Broughton
Down, Hampshire |
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