The fireflies in Japan signal the start of the summer season. And with the hot weather comes the stunning bioluminescent insects as they light up the night sky to attract mates and prey. The predominant breeds in Japan are the genji-botaru and heike-botaru, believed to be named after rival clans from the Heian period. They are bred in the city at the Itabashi Hotaru Breeding Facility and put on display for city dwellers. But the lightning bugs, or hotaru (firefly), are also visible in their natural environment amongst trees and grasses. The fireflies are a favorite subject of photographers during the May to June season.