The two Northern Lestids are very similar in appearance and can easily be confused. Males are best separated but viewing their anal appendages (see above).
- Lower appendages (shown black above) clubbed and inward turned - L. dryas
- .Lower appendages straight - L. sponsa
- bright blue eyes - 2nd abdominal segment (above) green in lower half - L. dryas
- dark blue eyes - 2nd abdominal segment predominantly powder blue - L. sponsa
The two species look similar but have quite different life styles and rarely occur together.