Firefly Watching on the Island

Updated: Aug 12, 2020

One of the more popular summer attractions in Japan among the locals is firefly watching. While it may not be apparent to a tourist, but it is a thing enjoyed throughout the country by both young and old. In most cases, however, you either have to be lucky to spot a glowing firefly or be guided by the said locals who know the exact locations. So, if you are interested in seeing these marvellous creatures in action on the island, read on!

The history of fireflies in Hachijojima

Around the world there are some 2000 species of fireflies, while in Japan, it is estimated that around 45 species exist; Heike-botaru (Aquatica lateralis), Genji-botaru (Luciola cruciata), and Hime-botaru (Luciola parvula) being the representative ones.

In Hachijojima, only two species exist: Heike-botaru and Genji-botaru.

In 1924, Hiko Mochimaru and Toku Ishii brought Aquatica lateralis (known as "heike-botaru" in Japanese), a species of firefly from Kanagawa prefecture to the island.
In 1965, Tokai Kisen Co., Ltd. introduced fireflies to Kamogawa River which has become their home.
In 1994, the locals introduced fireflies to Angawa River (in Nakanogo) which had become home to the creatures for a while, but is no longer being tended.

Nowadays, only the designated area by the Kamogawa river, known as Riverside Firefly Walk (or Hotaru-Suiro in Japanese), is being taken care of and awaits those who are interested in the fireflies.

the Firefly life cycle

Larva: June~

Larva hatch from eggs found in rocks, lichen, moss etc. and crawl to the bottom of the water. At first, they are around 5 mm. in length and while in the underwater, they feed off snails growing in size, and molt sheding off the skin 4~7 times.

Pupa: Around May next year

The larva move ashore and position themselves in the soft soil (beneath the lichen etc.) to become pupa. At this point, they start emitting very dim glow. Those which could not feed off enough, spend another year in the underwater and move ashore only the next year.

Adult: June-August

Once they mature, the adult fireflies leave the grounds and survive only by drinking dew off the leaves. Also, during this time males and females meet, and copulate. The female is said to lay up to a thousand eggs* which hatch after a month and the cycle repeats.

*Genji-botaru female lays 500~1000 eggs; Heike-botaru female lays 50~100 eggs.

hachijojima Firefly watching

a guided map of Hachijojima riverside firefly walk — Firefly watching map

Use the map on the right as a guideline for your adventures. Note that the orange path along the river is shared by both pedestrians and cars, however, as the waterway becomes dark, driving becomes dangerous, therefore everyone is encouraged to refrain from driving there past 19:00; use the parking spots marked white instead.

Firefly watching

When: late May~late July; in the evenings and/or at night

Where: Riverside Firefly Walk (Hotaru-Suiro)

Bring: flashlight (check manners*), appropriate footwear and guard against mosquitoes.

It is best to keep in mind that the fireflies are most active on hotter days after rain, darker/clouded evenings when the moon is hidden, and/or when the wind is barely present.

Manners

No catching

The adult fireflies have a body of as small as 1 cm. and a lifespan of only a few weeks at best. The act of touching them can inflict high stress which can further affect their already-so-short lifespan.

No powerful flashlights or flash photography

They are sensitive to light, and it should not be surprising that it is possible for them to die due to panic upon a powerful bright flash. When using a flashlight, try to limit the use only in the vicinity of your feet.

Attracting the firefllies

The use of blinkers, hazard lights, or similar ways to attract fireflies is something one should avoid. However, a red-colored light seems to be the least stressful, so wrapping your flashlights with a red cellophane or in a similar fashion to make the light red'ish is the way to go.

Remember: the manners set in place are not to make it difficult for someone to enjoy the fireflies, quite the opposite, it is to protect the fragile creatures while allowing many people to see them in harmony, therefore please abide by the above-mentioned points.