These were a breed of Ta-Metru winged insects nicknamed "fireflyers." Left alone, the small insects were relatively harmless. When a swarm was angered, they would pursue an enemy halfway across the city. The swarm gave off an ominous buzzing sound. Fireflyers were felled by cold temperatures.
Fireflyers were flying insects living in Ta-Metru with a fiery sting. Individually, they were harmless, but an angry swarm was capable of overcoming even a Toa Metru. They were known to nest in furnaces and in the maintenance tunnels beneath the metru.
Metru mantises preyed on fireflyers. Onu-Matoran at times released Metru mantises into mines and tunnels to clear out fireflyers and other insects living there.