Butterflies of
Britain & Europe
Adonis Blue
Lysandra bellargus
DENIS &
SCHIFFERMULLER, 1775
Family - LYCAENIDAE
subfamily -
POLYOMMATINAE
Adonis Blue
Lysandra bellargus, male, Hod Hill, Dorset ©
Adrian Hoskins
Introduction
The Adonis Blue
is found throughout most of the warmer parts of Europe, but is absent from
Norway, Sweden, Finland, the Mediterranean islands, and all except
the southern counties of Britain. Beyond Europe it also occurs in
Turkey, and eastward to the Black Sea.
In continental
Europe it is possible to confuse this species with several others
in the same genus. All members of the genus
Lysandra are characterised by
having chequered margins, which are not present in
Polyommatus,
Plebicula,
Agrodiaetus etc. The other members of
Lysandra have a much paler
silvery blue colouration, with the exception of the Spotted Adonis
Blue L. punctifera, which has
a series of sub-marginal black spots on the upperside wings.
Adonis Blue
Lysandra bellargus, male, Martin Down, Hampshire ©
Adrian Hoskins
The Adonis Blue,
like most other "Blues" is sexually dimorphic - only the males
have the beautiful overall electric blue colouration. In a
photograph it is impossible to convey the brilliance of the blue,
which glints in the sunshine and changes hue according to the
angle of view.
Females
by comparison are dark chocolate brown, with a dusting of deep
blue scales across the basal and median areas of the wings. The
extent of the blue dusting varies considerably between individuals
of the same population. All females also have a dark discal spot
on the forewings, and a row of orange sub-marginal lunules on the
hindwings. The female Chalkhill Blue is very similar, but slightly
larger and with a dull earthy brown ground colour. It also has
suffused whitish edging to the black sub-marginal spots on the
upperside, as compared to blue edging in
bellargus.
|
The Adonis Blue and many other species
have conspicuously coloured
males, but relatively plain females.
Males use "flash colouration" to confuse predators. If a bird sees
the butterfly in flight or basking on a flower, it targets the
bright blue image. The butterfly reacts to threat by settling
immediately on the ground and closing it's wings, revealing the
spotted greyish underside which is an effective camouflage when it
is settled on chalky soil.
Females are
surreptitious, tending to move very little until mated. When
searching for egg-laying sites they tend
to move slowly and deliberately, and for them,
plainer colours are a better means of defence.
Most female Adonis Blues are dingy brown in colour, with hardly
any blue scales, so they easily escape the notice of birds. The
female illustrated below is an exceptionally bright form, but
still far less conspicuous than the bright blue males.
|
|
 |
|
Adonis Blue
Lysandra bellargus, female, Ballard Down, Dorset ©
Adrian Hoskins |
Adonis Blues
sometimes hybridise with the Chalkhill Blue
L. coridon,
producing the hybrid
polonus,
but the progeny are infertile.
Habitats
In Britain the butterfly is confined to dry chalk and limestone grasslands in the
counties of Dorset, Somerset, Wiltshire, Hampshire, the Isle of Wight, Surrey,
West Sussex and Kent.
It
breeds in compact and dense populations comprising hundreds, or sometimes many thousands of
individuals. The populations however are extremely localised - breeding in a
restricted area of each site, even if the larval foodplant is widespread.
Furthermore movement of adults between nearby sites is extremely unusual - the
butterflies seem to find barriers such as roads, cultivated fields or tall
hedges virtually impassable.
Most
colonies are on south-facing slopes where horseshoe vetch grows in profusion,
and which are heavily grazed, producing a short sward pock-marked with little
patches of bare ground such as those caused by erosion, cattle poaching or
rabbit excavations. A very warm microclimate is essential, as even a minor
relaxation in grazing can bring about a major decline or local extinction. Many
colonies are restricted to very localised areas within their sites, e.g. along
the south facing ramparts of ancient hill forts, or the west facing bank of a
dyke.
In
Europe the butterfly is far less fussy about it's habitats, and can be found
flying along roadsides, or in areas of long grass and scrub on limestone plateaux.
|
 |
|
Adonis Blue
Lysandra bellargus, male, Hod Hill, Dorset ©
Adrian Hoskins |
Lifecycle
There
are two generations in Britain, the first emerging in May, and the second in
late August.
The
flat whitish eggs are laid on the underside of terminal leaflets of horseshoe vetch Hippocrepis comosa. There
are no alternative foodplants. The butterflies choose plants which are in full
sunlight, in sun-baked positions at the edge of rabbit scrapes, paths or other
patches of bare ground. The eggs are laid singly, but often several females will
visit a particular favoured plant, and consequently as many as 30 can be found
in very close proximity.
The
larvae feed diurnally. When tiny they feed on the under surface of the leaves
where they nibble here and there, producing tiny holes, but leaving the upper
cuticle intact. The feeding damage can be seen from above as a peppering of
microscopic shiny spots. When older the larvae rest on the upper surface of the
leaves but are very well camouflaged and difficult to spot.
They are commonly attended by ants Lasius niger, Lasius alienus
or Myrmica sabuleti. The ants are attracted by a sugary secretion which they milk from
a gland
near the caterpillar's tail. The larvae seem unable to survive without the ants, whose
presence deters other insects that would otherwise attack and kill them.
At dusk the larvae retreat to the
base of the foodplants, where they assemble in groups of about half
a dozen. They are followed by the ants which cover them in a thin layer of soil
particles, and stand guard over them during the night.
Adonis Blue larvae ( and those of most other Blues ) appease
their attendant ants by "singing" to them, thereby avoiding being eaten
themselves. It is not known how the larvae produce their song, although there
are microscopic knobs and plates around the opening of the honey gland which may
be involved.
Larvae of the second generation enter hibernation almost immediately after
hatching, and awaken to begin feeding in March.
When
fully grown they are deep green, each segment having a prominent hump. A series
of bright yellow dashes runs along each side below the spiracles, and a pair of
broken yellow stripes run along the back.
The
pupa at first is pale olive, but changes to become straw coloured after a
few days. It is formed in crevices on the
ground, but ants quickly cover it with a thin layer of soil. Sometimes pupae
have been found inside the brood chambers of ants. Immediately
prior to emerging from the pupal case, the butterfly produces a crackling song
to pacify the ants. It then rapidly breaks through the soil to crawl
up a stem where it hangs to dry it's wings.
Adonis Blue
Lysandra bellargus, male, Hod Hill, Dorset ©
Adrian Hoskins
Adult behaviour
Males
patrol almost incessantly back and forth across their habitat,
fluttering just above the sward in a constant search
for females. Periodically however they need to refuel, and stop
for a minute or two to nectar at the
flowers of horseshoe vetch, bird's foot trefoil, marjoram,
hawkbit or
thyme.
Occasionally they visit taller plants including thistles,
knapweeds and hemp agrimony. They have also been frequently
observed gathering to feed at animal droppings.
Adonis Blue
Lysandra bellargus, male, Cissbury Ring, West
Sussex ©
Adrian Hoskins
Females are seen far less
frequently as they are much less conspicuous, and are usually
mated before taking their maiden flight.
Copulation occurs without
preliminary courtship, at about midday. Copulated pairs, if
disturbed will fly a short distance to find a safer resting
place.
|
 |
|
Adonis Blue
Lysandra bellargus, copulated pair, Old Winchester
Hill, Hampshire ©
Adrian Hoskins |
In hazy sunshine, butterflies of
both sexes, including copulated pairs, will bask in rabbit
scrapes or other bare patches, with their wings held partly or
fully open.
On sunny days, as dusk approaches,
the butterflies congregate to roost on grass-heads in
sheltered areas where tall grasses receive the final rays of the
setting sun. They roost head-downwards, often in groups of 20 or
30, with up to 5 individuals on each grass-head.
|
