FireFlieS FireFlieS EmiT light mostly to Attract mateS, Although they also communicate for other reasons as well, Such as to defend territory and warn predators away... In some firefly Species, Only one sex lights up.. In most, however, Both sexes glow; often the male will fly, while females will wait in trees, shrubs and grasses to spot an attractive Male...If She finds one, she'll signal it with a Flash of her own.. Please Rate and Vote my Topic here topic id: 3203727