Large Blue

Maculinea arion (mak-you-LIN-ee-uh a-RY-on)

Large Blue - Daneway - 25th - June - 2014
Photo © Maximus

Male: 38 - 48mm
Female: 42 - 52mm

Checklist Number

Family:LycaenidaeLeach, 1815
Subfamily:PolyommatinaeSwainson, 1827
Tribe:PolyommatiniSwainson, 1827
Genus:MaculineaEecke, 1915
Species:arion(Linnaeus, 1758)
Subspecies:arion (Linnaeus, 1758)
 eutyphron (Fruhstorfer, 1915)

< Previous SpeciesNext Species >


This butterfly was first recorded as a British species in 1795 and, even then, was considered a rare insect. Due to the loss of suitable habitat, the endemic subspecies of Large Blue became extinct in the British Isles in 1979, the last site being on Dartmoor in Devon.

This magnificent insect has since been "brought back from the dead" through the dedication of several conservation organisations and many individuals. After its extinction in the British Isles in 1979, the Large Blue became the subject of a highly-organised reintroduction programme, using stock from Sweden. The estimated number of adults flying in 2006 was 10,000 on 11 sites, which is the largest number seen in the British Isles for over 60 years. This is a magnificent example of conservation in action.

The successful reintroduction of the Large Blue is made even more remarkable when one considers its elaborate lifecycle. The larva is parasitic in that it feeds on the grubs of a red ant, Myrmica sabuleti, on whom its existence depends. Although the dependence on ants had been known for many years, the dependence on a single species of ant, in order to maintain a viable population, was unknown to conservationists for many years until Jeremy Thomas discovered the association in the late 1970s. Unfortunately, the discovery came too late to save the native population. Today's reintroduction efforts focus as much on the population of ants present, as they do on the Large Blue itself.

Anyone wanting to see this species in the British Isles should visit the open access site at Collard Hill in Somerset. A "Large Blue Hotline" is usually set up each year that provides an up-to-date status of the emergence at this site. Details are available on the Butterfly Conservation website. In addition, Butterfly Conservation members and Somerset Wildlife Trust members have the opportunity to visit a private site, Green Down, each year, although places are limited. The majority of reintroduction sites are in the south-west of England, notable colonies being in the Polden Hills in Somerset, Dartmoor and Gloucestershire.

Taxonomy Notes

Le Chamberlain (1908) names the aberration ab. cotswoldensis of Lycaena arion, defined as "Aberration of male and female with all the wings more or less thickly sprinkled with black scales, giving it a very dusky or melanic appearance, constituting an approach to the alpine var. obscura of Professor Christ. Scarce.". Goodson & Read (1969) promote the aberration to subspecies, making ssp. cotswoldensis, since the definition clearly provides a contrast between specimens from the Cotswolds and those found in Devon and Cornwall.

Maculinea arion ssp. arion

This species was first defined in Linnaeus (1758) as shown here (type locality: Europe).

The reintroduced British population is represented by the nominate subspecies.
Large Blue - Collard Hill, Somerest 18-June-2014

Photo © Neil Hulme

large blue male, underside collard hill 09

Male Underside
Photo © geniculata

Large Blue female - Daneway Banks 19-June-2015

Photo © Neil Hulme

Large Blue Female - Collard Hill - 19.06.12

Female Underside
Photo © PhiliB

Photo Album ...

Maculinea arion ssp. eutyphronHistoric Specimens

This subspecies was first defined in Fruhstorfer (1915) as shown here (type locality: Cornwall, England).

This subspecies was endemic to the British Isles and is now, unfortunately, extinct. Two of the larger populations were found in the Cotswolds and the north Cornwall coast, extending into Devon at its eastern edge.

Ford (1945) describes the differences between several populations: "On the Cotswolds it appears in June or even in late May, and it is of a rather dark iron-blue shade. The species emerges a little later in Cornwall, where the specimens are of a clearer and brighter blue, while the spots on the upper-side are rather larger, though they may be less numerous that in the Gloucestershire examples. The extinct race from Barnwell Wold, Northants ... more nearly resembled the Cotswold insects. Ancient specimens from the Langport district of Somerset, where the species is also presumably extinct, are similarly of the darker blue shade, but they are remarkable for the large size of their spots, either on the upper or the under-side of their wings, or both. Those from the Salcombe district of South Devon on the whole resemble the Cornish form, though some of the specimens are of rather a duller tint ... It is clear that in England there is a tendency for the Large Blue to be of a brighter colour in the peninsula of Devon and Cornwall than elsewhere, though the discontinuity is not a large one. Somerset specimens tend to bridge the gap between the south-western habitats of this butterfly and those of the Cotswolds".

Maculinea arion ssp. eutyphron (Fruhstorfer, 1915)

Original (German)

♂♂ in der Regel relativ klein, bleich, Vorderflügel meist nur mit vier unbedeutenden Punktflecken. Weiblich nur wenig kräftiger schwarz umrahmt als der männlich. Patria: England, Cornwall, eine Serie in Kollektion Ch. Blachier. Nach Oberthür ist damit die Rasse der Bretagne identisch.


Males as a rule relatively small and pale, the forewing with at most four weak spots. The female only slightly darker-bordered than the male. (Type?) locality: Cornwall, England, a series in Ch. Blachier's collection. According to Oberthür the race from Brittany is identical with it.

Large Blue - Male Upperside [Richard Lewington]

Photo © Richard Lewington

Large Blue - Male Underside [Richard Lewington]

Male Underside
Photo © Richard Lewington

Large Blue - Female Upperside [Richard Lewington]

Photo © Richard Lewington

Large Blue - Female Underside [Richard Lewington]

Female Underside
Photo © Richard Lewington

Photo Album ...

Conservation Status

It is generally agreed that the demise of the native population of this species was not the result of over-enthusiastic collectors, but large-scale habitat loss. The presence of this butterfly in the British Isles today is the result of a coordinated and ongoing conservation effort.

UK BAP StatusDistribution Trend (%)Population Trend (%)
Priority Species
Click here to access the Biodiversity Action Plan (BAP) for this species.
Large Increase+100
Large Increase+271

The table above shows the distribution and population trends of species regularly found in the British Isles. The distribution trend represents a comparison between data for the periods 1995-1999 and 2005-2009. The information provided is taken from the Butterfly Conservation report The State of the UK's Butterflies 2011. The UK BAP status is taken from the UK Biodiversity Action Plan (UK BAP) (2007 review).


The Large Blue requires fairly closely-grazed grassland, where Wild Thyme is found in abundance, and where the host ant is able to flourish in good numbers. Overgrown conditions result in a cooler ground temperature, and a smaller population of ants as a result. Typical sites are on a south-facing slope that receives the full benefit of the sun.



Click here to see the distribution of this species or here to see the distribution of this species together with specific site information overlaid.

Life Cycle

This butterfly has one generation each year. The adult butterfly is seen from the middle of June, peaking toward the end of June. However, recent years have seen the adults emerge unusually early, with a peak in mid-June.

Maculinea arion ssp. arion

The chart(s) above have been correlated with the phenology plot below, taken from the UK Butterfly Monitoring Scheme. The blue line gives average counts over the full data set from 1976 to date, and the red line gives the average for the last year.


This is a warmth and sun-loving butterfly. In bright sunlight the adults rarely bask with their wings open, and this is one of the few butterflies where photographers welcome intermittent sunshine or overcast conditions, when the adults will bask with their wings held open, revealing the characteristic pattern on the forewings.

After emerging, females typically fly to the bottom of the slope, where they are intercepted by males in search of a mate. The couple mate without any discernable courtship and remain together for an hour or so, after which the female rests and takes nectar. After another hour or so, the female will commence her search for plants on which to lay. Females are often seen probing the unopened flower heads of Wild Thyme with their abdomen, only to find that no egg has been laid, presumably because the flower head is deemed unsuitable. However, if a suitable plant is found, then the female typically lays a single egg, although 2 or 3 eggs may be found on the same flower head on occasion. This is presumably from different females since the larvae are cannibalistic while in the first instar.

Adults feed primarily on Honeydew / Sap. Bugle (Ajuga reptans), Carline Thistle (Carlina vulgaris) and Thyme (Thymus polytrichus) are also used.

Photo Album ...


The white eggs are laid singly in the flower heads of Wild Thyme. Eggs are laid only in those flower heads that have not yet fully-opened, and are still relatively compact. The eggs hatch in 5 to 10 days.

Large Blue Ovum - Collard Hill - 24/06/14

Photo © William

Large Blue - ovum - Collard Hill - 20-Jun-12-2-2

Photo © Pete Eeles

Large Blue - ovum - Green Down - 12-Jun-08 (2)

Photo © Pete Eeles

Large Blue (2) [Nick Sampford]

Photo © Nick Sampford

Photo Album ...


The newly-emerged larva leaves the egg without eating the shell, and proceeds to feed on the flowers of Wild Thyme, which is its sole food source for the first 3 instars. The first 2 instars feed inside the flower head, while the 3rd instar is more exposed and may even move to new flower heads. However, with a change into the 4th instar, a distinct change in behaviour occurs. The larva will drop to the ground in the hope of being found by a red ant. An ant taps the larva once located, causing the larva to secrete a droplet from a special gland, called a Newcomer's gland, located on its 7th segment. This process is sometimes referred to "milking" the larva.

Eventually, after a period a 30 minutes to 4 hours, the larva distorts its body, by rearing up on its prolegs, to give the illusion of being an ant grub. On realising this, the ant immediately picks the larva up in its jaws, and carries it back to its nest where it lives alongside the ant grubs which, unknown to the ants themselves, form its future diet.

The figures below are taken from Frohawk's classic work, "Natural History of British Butterflies". The first shows the larva's disposition when feeding on the foodplant. In the same figure we can see the hunched profile of the larva before it is picked up by an ant. The second figure shows the ant picking up the larva before taking it back to its nest.

Highslide JSHighslide JS

The larva overwinters while in the 4th instar.

The primary larval foodplant is Wild Thyme (Thymus polytrichus). Wild Marjoram (Origanum vulgare) is also used.

Large Blue - larva - Unknown location - Unknown date (2) [Jeremy Thomas]

Photo © Jeremy Thomas

Large Blue - larva - Nr. Stroud - 20-Jul-12-11

Photo © Pete Eeles

Large Blue - larva - Nr. Stroud - 20-Jul-12-13

Photo © Pete Eeles

arion adoption [Marcin Sielezniew]

Photo © Marcin Sielezniew

Photo Album ...


The pupa is formed in the ant chamber. It is attended by the ants which keep it clean. On emerging from the pupa, the butterfly crawls through the ant chamber to the surface, where it crawls up nearby vegetation before expanding its wings.

Large Blue - pupa - Unknown location - Unknown date [David Simcox]

Photo © David Simcox

arion pupae  in nest [Marcin Sielezniew]

Photo © Marcin Sielezniew

Photo Album ...


Description to be completed.

Click here to see the aberration descriptions and images for this species.

Similar Species

No similar species found.


Watch Video
Watch Video
Watch Video

The following links provide additional information on this butterfly.


The species description provided here references the following publications:

Eecke (1915) van Eecke, R. (1915) Bijdrage tot de kennis der Nederlandsche Lycaena-soorten. Zoologische Mededeelingen.
Ford (1945) Ford, E.B. (1945) Butterflies.
Fruhstorfer (1915) Fruhstorfer, H. (1915) Societas Entomologica.
Goodson & Read (1969) Goodson, A.L. and Read. D.K. (1969) Aberrational and Subspecific Forms of British Lepidoptera (unpublished work, British Museum of Natural History) .
Le Chamberlain (1908) Le Chamberlain, C. (1908) Lycaena arion in the Cotswolds. The Entomologist.
Leach (1815) Leach (1815) In Brewster: The Edinburgh Encyclopaedia.
Linnaeus (1758) Linnaeus, C. (1758) Systema Naturae. Edition 10.
Swainson (1827) Swainson, W. (1827) A Sketch of the Natural Affinities of the Lepidoptera Diurna of Latreille. The Philosophical magazine : or Annals of chemistry, mathematics, astronomy, natural history and general science.