The Fireflies of Arimagawa River

Some dozen years have passed since the Arima Elementary School began striving for an "Arima Onsen that is kind to people and a firefly elementary school." In cooperation with the Recycle Promotion Section of the Kobe City Environmental Bureau, the student council, and the Arima Onsen Tourism Association, the entire school body became involved in the breeding and stocking of fireflies in 1991 with the motto of "Let's beckon a return of the fireflies to Arima."

▲Click here to enlarge the map.▲

Two popular sightseeing spots near the Arima Onsen Station of the Rokko-Arima Ropeway are Tsuzumigataki Waterfall and Masu-ike Pond. The river flowing from the waterfall is called Takigawa River. Here the river runs into the Rokkogawa River near Nene-bashi Bridge, and this forms Arimagawa River. Passing beneath the Taiko-hashi Bridge near the Arima Onsen Station of the Kobe Railway, Arimagawa River flows under the Koen-bashi Bridge, which is near the Arima Elementary School, and the Otokura-bashi Bridge, which is further downstream. It continues along going north until it finally joins the upper parts of the Mukogawa River.

Those visiting Arima Onsen with the intention of appreciating the beauty of the fireflies can enjoy the sight of them at night on the riverbanks downstream from the Masu-ike Pond on Takigawa River and the area spanning from Koen-bashi Bridge to the Otokura-bashi Bridge.

Etiquette for Appreciating Fireflies

• Fireflies detest light, so be sure to turn off your car lights.
• It is better to avoid creating loud noises and be quiet.
• Although fireflies are not afraid of humans and will fly near us, let's not catch them and take them home with us.
• Let's not leave cigarettes or any trash behind.

Habitat

Fireflies can live anywhere near a river if the water is clean and not polluted by agricultural pesticides or synthetic detergent.

Types of Species

Around 2,000 species of fireflies can be found all over the world with 40 types found in Japan. Of the fireflies seen in Japan, the most common are the three types described below. The type of firefly commonly seen at Arimagawa River is the Genji Firefly (Luciola cruciata Motschulsky).

Comparison of the Three Types

Type	Genji Firefly (Luciola cruciata Motschulsky)	Heike Firefly (Luciola lateralis Motschulsky)	Hime Firefly (Luciola parvula Kiesenwetter)
Photograph
Body length	10-20mm	10-18mm	5mm
Illumination cycle	2 second intervals	1 second intervals	0.5 second intervals
Luminescent-color	Yellow	Yellow	Rose pink
Habitat	Small clean river, irrigation channel	Rice paddy, irrigation channel, small clean river	Cedar, white cedar forest, etc.
Food for larva	Melanian snail	Sinotaia quadrata histrica (pond snail), Austropeplea ollula (Japanese ear snail), Physa acuta, etc.	Allopeas clavulinum Kyotoense, Clausiliidae, etc.
Appearance (in general)	Beginning of June to the end of June	Middle of June through the early part of July	Early June to late July
Number of eggs	400-1000 eggs	70-100 eggs	50-100 eggs

Life Expectancy

Lifetime is about 10-14 days for both males and female after becoming imago (adult firefly).

Mode of Life

▲Click here to enlarge "Firefly Development".▲

Fireflies cast off their skin as larva five times, go ashore, and cast off their skin once more after forming a cocoon. They spend nine months as larva on the river, go ashore in April when it rains, and make a cocoon in the ground. They become pupa and emerge around fifty days later. When they become imago (adult firefly), they don't eat and only come out at night.

Chance for Appreciation

Genji fireflies can often be seen on dark, cloudy, sultry evenings but are not active when temperatures drop. Peak times for these fireflies are 8:00-9:00 pm or in the dead of night from 12:00-1:00 am or 3:00-4:00 am.

The fantastical illumination emitted by fireflies involves the same mechanism for light as found in the oxidation reaction of a burning candle.
In the luminescent organ of the firefly, there is a luminous substance called luciferin that reacts to oxygen in the air to emit light.
Usually oxidation at the time of a reaction emits heat and light, but the enzyme luciferase within the luminescent organ of the firefly efficiently oxidizes without expending a great deal of energy and changes to light.
Furthermore the faint glow of light and darkness is linked to breathing. When it breathes, the membrane blocking the light is lowered, and light is extinguished.