A firefly on someone's palm

Fireflies in Japan

In the land of the rising sun, fireflies are the image of summer. Many cities throughout Japan even host firefly viewing festivals, where locals and visitors alike are welcome to marvel at the beautiful flashes of light that these insects use to either attract a mate, signal distress, or warn off predators.

There are approximately 2,000 species of fireflies worldwide, and can be found on every continent except Antarctica. 40 of these species live in Japan with over 9 found in Tokyo alone. The most well-known fireflies, however, are the ‘Genji Botaru’ and the ‘Heike Botaru’.

The Genji and Heike Botaru

The ‘Genji Botaru’ or the ‘Lampyridae, Luciolinae, Luciola Cruciate’, is named after the Genji, or Minamoto clan. Likewise, the ‘Heike Botaru’, or ‘Lampyridae, Luciolinae, Luciola Lateralis’ is named after the Heike, or Taira Clan. In history, these two clans fought against each other for control of Japan in the 12th Century. It is thought that as the war between the two clans ended in early summer, when fireflies are predominantly seen, the souls of the lost soldiers in the battle between the two clans turned into these fireflies. Adding to this belief, the name ‘Genji’ was given to the larger of the two species, as it was the Genji Clan that held victory over the Heike in the Genpei Wars.

These names, however, do not depict the nature of these fireflies, as the Genji and Heike Botaru are delicate and docile creatures. These insects, or beetles, have a four-stage life cycle. They start out as bioluminescent eggs, laid in the hundreds on moss next to clean rivers or streams. After about a month, these eggs hatch to produce larvae. At this stage, these fireflies spend the fall and winter at the bottom of a river, feasting on snails. In the spring, these larvae climb out of the water and build a mud chamber underground where they take on their pupa form, which can take up to 5 weeks! They develop a lot at this stage and stay in pupa form for a further 2 weeks or so before emerging as adult fireflies.

The glow of a firefly

Despite both fireflies being common throughout Japan, there are a few differences to take note of.

The first is that the Genji Botaru are larger than the Heike Botaru with a 7-8mm difference. They also have distinct markings at the top of their backs. While both species of firefly have a segment of red separating their heads from their abdomens, the Genji Botaru has a black cross-like symbol in the middle of that red segment. The Heike Botaru, on the other hand, has a thick vertical line going through it.

A firefly in a plastic container

Even their environments are slightly different. The Genji Botaru only eat thiaridal snails – snails that require fresh water in which to live in. So, if this food source disappears from an area due to water pollution, then this species of firefly will also cease to inhabit that area. The Heike Botaru, however, are much more resilient to water pollution as their diet consists mainly of pond snails and mud snails.

Despite the Heike Botaru’s resilience, however, their population is also on a slow decline with the increased usage of pesticides on rice crops – a prime location to find Heike Botaru.

Other Fireflies in Japan

Photo by suki tamba on Flickr.

Other somewhat-known firefly species in Japan are the ‘Akimado Botaru’, the ‘Tateobikushi Hige Botaru’, the ‘Suji Gurobeni Botaru’, the ‘Oomado Botaru’, the ‘Oooba Botaru’, the ‘Oba Botaru’, the ‘Munekuri Iro Botaru’, the ‘Haneaka Hotaru Modoki’, the ‘Okinawa Suji Botaru’, and the ‘Hime Botaru’.

Though some of these fireflies are much rarer than others, they can be found in Japan as well. As with every firefly, however, they all prefer natural environments. Loud noises, such as shouting or laughing too loudly can scare them away. Artificial lights also seem to confuse and scare these insects, so it is best to take pictures without the use of flash. In addition, many local festivals will ask that you take your trash home with you as littering in an environment with fireflies can prove detrimental to the growth of their species.

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