Demeter Firefly Cologne Spray By DemeterDemeter Firefly Perfume by Demeter, For any kid who grows up east of the rockies, one of the most treasured signs of spring is the first firefly of the season. In the north, fireflies are a sure sign of winter having broken its grip and summer vacation is right around the corner! demeter firefly is a brilliant scent, capturing the smells and excitement of those spring evenings on the cusp of summer.