Large Blue
Key facts
- Latin name
- Phengaris arion
- Family
- Lycaenidae
- Wingspan
- 30-44 mm
- Flight season
- June — August
- Host plants
- Wild thyme, Oregano
- Conservation status
- VU
Appearance
The large blue (Phengaris arion) is the largest blue in Russia with a wingspan of 30–44 mm. Males: upper side of the wings bluish gray with a row of black rounded spots on the forewing. Females are somewhat darker.
The underside of the wings is gray-brown with black spots and white rings. A white fringe runs along the wing margins.
Range and habitat
Found in Europe and temperate Asia. In Russia in the European part and Siberia.
Strictly tied to limestone meadow slopes and clearings with thyme and colonies of Myrmica ants. It requires a specific combination of conditions.
Unique life cycle
Early caterpillars feed on thyme flowers. In the fourth instar the caterpillar drops to the ground. Encountered Myrmica sabuleti ants "adopt" it — it releases substances mimicking chemical signals of ant larvae. In the nest the caterpillar overwinters, feeding on ant larvae, and pupates inside the colony.
Conservation
IUCN status VU (Vulnerable). Listed in the Red Data Book of Russia. The main cause of decline is cessation of moderate grazing, leading to overgrowth of thyme clearings.