1. plural of ephemerid; insects of the order Ephemeroptera, commonly known as mayflies, characterized by short adult lifespans and aquatic nymphal stages.
Usage: technical/scientific; plural form

Examples

• The stream was filled with ephemerids during their brief mating season.
• Ephemerids are important indicators of water quality in freshwater ecosystems.
• Fishermen study ephemerids to understand what trout feed on.
• The nymphs of ephemerids can live underwater for up to two years before emerging as adults.
• Ephemerids typically live only a few hours to a few days in their adult form.