Japanese Oakblue

Beautiful bluish-purple gradation.

Scientific name	Narathura japonica
English name	Japanese Oakblue
Japanese name	紫小灰蝶
Class	Insecta
Order	Lepidoptera
Family	Lycaenidae
Genus	Narathura
Species	japonica
Full length	30-40mm
Distribution	South of Miyagi Prefecture

Japanese Oakblue Characteristics and Morphology

A beautiful lycaenid butterfly with bluish-purple wings. Wingspan is approximately 4 cm. The color is almost the same in both sexes, but the distribution of colors on the wing surface differs.
The head is brown. Palpi are slightly protruding. The body is brown to gray. The upper side of the wings is glossy bluish-purple on the inside, with the purple becoming darker from the head towards the abdomen. The edges are brownish, almost black. The underside of the wings is light brown with slightly darker brown markings like stains.

Male

The purple area on the upper side of the wings is larger. The brown part of the edge is thinner compared to the female.

Female

The brown part of the edge on the upper side of the wings is thicker compared to the male, and the purple part is smaller.

Japanese Oakblue Ecology

Habitat

Found in forests and parks.

Food

Rarely sips nectar from flowers, more often observed drinking water. The larvae feed on the leaves of evergreen trees of the beech family, such as *Castanopsis sieboldii* and *Quercus glauca*.

Life Cycle

Appears from spring to autumn. As they grow, they build nests using leaves. They hatch in fallen leaves on the ground.

Japanese Oakblue Photos

Japanese Oakblue Photos are introduced.
Tap the photo to open the detail page.

The gradation from blue to purple is beautiful.

The underside of the wings is light brown with markings.

Japanese Oakblue Behavior

Perches on leaves and branches, or flies around trees. It does not usually fly very far.

Japanese Oakblue Information

The larvae secrete honeydew to attract Aphaenogaster ants, and by suppressing the activity of dopamine in the ant's brain, they manipulate their behavior, causing them to guard the larvae. This has been considered a 'mutualism' where each organism benefits, but according to research published in July 2015 by a joint research group from Kobe University Graduate School of Science, Project Assistant Professor Ken Hojo, the University of the Ryukyus, and Harvard University, it was suggested that the larvae of Narathura japonica may be intentionally controlling the Aphaenogaster ants.

Japanese Oakblue Found Locations

Tama Forest Science Garden

I found a *Narathura japonica* perching on a leaf in the Tama Forest Science Garden in Hachiōji. It flew around the shrubs and rested quietly when it stopped on a leaf. It did not appear to be sipping nectar from flowers. I was surprised by the difference between when it opened and closed its wings.