Butterflies of Britain
Family - LYCAENIDAE
Celastrina argiolus, 1st brood male,
Purbeck Hills, Dorset ©
This is a very widely distributed species, found
throughout the temperate regions of Europe, in North America from
Alaska to Panama, across temperate Asia to Japan, and in Africa
north of the Sahara. Another very similar species
Celastrina lavendularis is found in the
temperate highland areas of India and south-east Asia, and 2 further
Celastrina species are found in
Indonesia and Papua New Guinea.
Celastrina argiolus, 2nd brood female,
Broughton Down, Hampshire ©
The distinctive black
wing-tips of the female ensure that it can't be mistaken for any
other European species, but the male can be confused in flight with
the Common Blue, which also sometimes flies in scrubby habitats. The
underside of the Holly Blue however is quite different, being a
highly reflective silvery blue, with tiny black dots and dashes.
Like most British
butterflies, the Holly Blue has had several earlier vernacular names
which have since fallen into disuse. The male of this species was
once called the Wood Blue or Azure Blue, while the female, which
early entomologists thought was a different species, was known by
the very apt and descriptive name "Blue Speckt Butterfly with Black
the Holly Blue is largely confined to England and Wales, although
there are very sporadic records from Scotland and Ireland.
is adapted to utilise a wide range of common larval foodplants
including non-native ornamental species. Consequently it can be
found in gardens and city parks as well as at woodlands, heaths, old
quarries and railway cuttings.
Most habitats tend to be
sheltered, but I have on several occasions seen pristine Holly Blues
flying rapidly across open heathland e.g. in the New Forest (
Hampshire ) and Wareham Heath ( Dorset ). From the latter
observation it is apparent that the butterflies are highly mobile,
and able to colonise new sites quickly. This mobility and the
polyphagous nature of the larvae, ensures that the species is widely
and evenly distributed within its range.
Throughout it's range, the species is double brooded. In Britain,
butterflies of the first brood begin emerging in March at the
warmest sites, but April or May is more typical. The second brood
flies from July until mid August. There is occasionally a partial
third brood, emerging in September and October.
Older literature suggests that the butterfly oviposits on holly in
the spring, and on ivy in the summer, but both broods in fact use a
very much wider range of larval foodplants.
The eggs of the first
brood are laid
singly on flower buds of holly Ilex aquifolium,
dogwood Cornus sanguinea, gorse
Ulex europaeus, or buckthorn
Rhamnus catharticus. The second brood
oviposit on flower buds of ivy Hedera helix,
privet Ligustrum vulgare, heather
Calluna vulgaris, alder buckthorn
Frangula alnus, bramble
Rubus fruticosus, rowan
Sorbus aucuparia and various other
bushes and shrubs including cultivated snowberry and
Pyracantha. The eggs are nearly always
laid on bushes growing in warm sunny and sheltered situations. They
hatch after about a week.
green slug-like caterpillars feed nocturnally on the flower buds,
developing seeds and berries of the various foodplants, and rarely
on the young tender leaves. They habitually sit on the skin of a
berry, with their head buried inside it. The caterpillar is easy to
find, either by searching directly, or by looking for half eaten
berries in which the caterpillar has left a distinctive circular
well as the plain green form of the caterpillar, there are also
forms with prominent whitish and purplish markings. In common with
most Lycaenids, the larvae are attended by various species of ants,
which obtain sugary secretions from a gland on the caterpillar.
larvae are parasitised by a host-specific ichneumon wasp
which has a very pronounced effect on Holly Blue abundance. In
certain years, when climatic conditions favour the parasitoid, the
butterflies can be extremely scarce. However when mild winters are
followed by hot summers the wasps emerge out of synchrony with the
caterpillars, and consequently in such years the butterflies are far
dark brown pupae are virtually impossible to find in the wild, but
in captivity they are attached by a silken girdle to a twig or dead
leaf. In nature they are probably formed in crevices in tree bark,
or amongst leaf litter on the forest floor. The species over-winters
in the pupal stage.
Most of the "blues"
found in Britain and Europe form breeding colonies of dozens, hundreds
or even thousands. They generally inhabit open grassy habitats and fly
close to the ground. In contrast the Holly Blue is nearly always
encountered singly, and found in the vicinity of bushes, shrubs and
the lower branches of trees. It is also very unusual in that it is
more commonly encountered in gardens and parks than in the wild
Blues commonly feed on the aphid secretions ( honey dew ) which coats
the upper surface of ash and oak leaves, but also sometimes
on the ground to feed at bird droppings or imbibe moisture from damp
paths. Additionally, in spring they nectar at hawthorn, daisies and
wood spurge. The second brood nectars on a wider range of plants
including bramble, hemp agrimony, fleabane, bell heather, cross-leaved
heath, hogweed, cow wheat and burdock.
feeding they always keep their wings closed, but in the hazy sunshine
of early evening they often settle on bushes to bask, holding their
wings partly open.