**Description:** Aquatic insects with two pairs of flat-folded wings and two long tails (cerci). Nymphs have flattened bodies to cling to stones.
**Size:** 0.5 to 1.5 inches long depending on species.
**Sexual Dimorphism:** In many species, males are smaller than females.
**Identification:** Their presence is the ultimate biological indicator of exceptional water purity and high oxygen levels.
**Habitat:** Clean, cold mountain streams like those in the Hearts Content area.