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Large Blue (Phengaris arion)

Large Blue

The Large Blue is a species of butterflies from the ‘blues’ family. Though it is not really a large butterfly in the true sense of the term (but rather medium, in general), they have actually been named so to differentiate them from the relatively smaller ‘Small Blue’ species that has an almost similar coloration pattern. The large blue has been declared to be ‘Near Threatened’ by the IUCN 2.3.

Scientific Classification

  • Family: Lycaenidae
  • Genus: Phengaris
  • Scientific Name: Phengaris arion

Description and Identification


Large Blue Butterfly Caterpillar i.pinimg.com

The larva emerges measuring only about 0.79 mm, and with a pale ochreous-yellow color tinged with greenish hues. On its upper side, there are longitudinal rows of serrated hairs that grow in pairs on each side of the caterpillar’s body segments and are curved backward.

The insect undergoes four instars before and spends up to 9 months before transforming into a pupa and feed on the leaves of its host. They exhibit a unique parasitic relationship with a red ant species, Myrmica sabuleti. The caterpillar hibernates in the winter in the hole of a particular species of red ant, Myrmica sabuleti, using a natural mimicry behavior.


Large Blue Butterfly Pupa ukbutterflies.co.uk

If the winter months coincide with this stage, they wait for the spring to come before emerging as a butterfly. The chrysalis is around 12.7 mm long. The creature has a faint apricot-yellow hue that gradually deepens to a dark amber shade, except over the wings.

Adult Butterfly

Sexual Dimorphism: Not distinctly present

Color and Appearance: When the wings are open, both the pairs of wings display a very bright blue with the forewings having several spots in dark gray to blue, and in shape resembling sesame seeds, while the outer end of the wings has gray borders. The hind wings, too, are thickly bordered with the same color as the other two. When the wings are closed, the striking absence of the cyan blue can easily be seen. Instead, they are mostly grayish beige. Also, both the wings display black spots of varied shapes bordered with bluish white. The females are somewhat lighter in coloration than the males.

Large Blue Butterflies

Large Blue Butterfly

Average wingspan: Up to 2 in (50.8 mm)

Flight pattern: Average and even


Large Blue Butterfly Eggs ukbutterflies.co.uk

Very flat and semi-globular with a pale bluish white color, deposited on the thymus of a blooming bud

Quick Facts

DistributionWidely distributed throughout Europe except for the extreme north and southern parts of Spain
HabitatPrefers south-facing hillsides with close-cropped, unfertilized pasture
Lifespan of adultsA few weeks
Host plantsThyme and wild marjoram oregano
Adult dietFlower nectar

Did You Know?

  • Before searching for a good habitat, they first look out for the caterpillar’s food plant – wild thyme, as also, the presence of the Myrmirca sabuleti red ant species.
  • The large blue has always been a rare butterfly in Britain, and moreover, went into extinction in 1979, after which, it was successfully reintroduced from continental Europe.

Large Blue Butterfly Images

Large Blue Butterfly Life Cycle blogs.discovermagazine.com

Phengaris arion

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Scientific Classification

  • Family: Lycaenidae
  • Genus: Phengaris
  • Scientific Name: Phengaris arion
Published by Avatar on November 1, 2018.
Last Updated: July 29, 2023. ✅ Verified by: Butterfly Team