Loomis Shijimi Habitat

A Butterfly Habitat on Kasugayama

The Loomis Shijimi Habitat (ルーミスシジミ生息地, Rūmisu Shijimi Seisokuchi) is a habitat of the Loomis shijimi, a small blue butterfly, on Kasugayama in Kasugano-cho, Nara City, Nara Prefecture, which in 1932 was designated a Natural Monument.

The Agency for Cultural Affairs names Nara Prefecture as the managing body, appointed in May 1932. The designation falls under the criterion for animals well known in Japan, though not unique to it, that need protection, together with their habitats.

The Agency gives no area or boundary, only the location Kasugano-cho. Nara Prefecture lists the Loomis Shijimi Habitat among the natural monuments of Nara Park, alongside the Kasugayama Primeval Forest, a Special Natural Monument.

Why It Was Designated

The designation text preserved in the Agency's database calls the Loomis shijimi a rare butterfly in Japan, living in large numbers in thickets of Japanese andromeda under a canopy of evergreen oak, and concludes that the site is remarkable as its habitat.

Nara Prefecture's draft conservation plan for the Kasugayama Primeval Forest records that in 1929, a commissioner of the Ministry of Education surveyed the birds, mammals and Loomis shijimi of Kasugayama. Road building was then altering the forest, and the butterfly's habitat was already seen as something to protect.

The Loomis Shijimi Butterfly

The Nipponica encyclopedia describes the Loomis shijimi as a butterfly of warm evergreen broadleaf forest from the Kanto region southwest, known from only a few places. Its Japanese name honours Loomis, the American missionary who first collected the Japanese subspecies.

Its caterpillars eat the leaves of the evergreen oak ichiigashi. The Kasuga Primeval Forest Conservation Project notes that large ichiigashi trees still grow in the forest around the Loomis Shijimi Habitat, and that this is the tree the butterfly depends on.

Nara Prefecture's red list places the Loomis shijimi (Arhopala ganesa loomisi) in its category of species on the verge of extinction in the prefecture.

A Butterfly That Has Vanished Here

The Loomis shijimi of Kasugayama is now said to be extinct, as the Nipponica encyclopedia also states.

The Kasuga Primeval Forest Conservation Project says it is thought to have died out after the Isewan Typhoon of 1959 brought down many of the ichiigashi trees it depended on, followed by pesticide spraying. No official study confirming the cause could be found.

The same project recalls a newspaper report of the butterfly's rediscovery on Kasugayama that was later corrected: the insect had been the similar Japanese oakblue. The Natural Monument designation remains in force.

Visiting the Loomis Shijimi Habitat

There is no marked plot or display for the Loomis Shijimi Habitat. To visit, walk the Kasugayama trail that circles the primeval forest. Nara Prefecture gives the trail as 9.4 kilometres long, and to protect the forest it prohibits leaving the paths, lighting fires and taking plants or animals.

From JR Nara or Kintetsu Nara Station, take the Nara Kotsu city loop bus (outer circuit) to Wariishi-cho, then walk about 15 minutes to the start of the trail. You can also take a bus to Kasuga Taisha Honden and walk about 10 minutes to join the trail. Enquiries go to the Nara Park Office on 0742-22-0375.