| 1a. Occiput with transverse row of evenly spaced spinules; Abdominal terga with numerous spinules. |   |
| 1b. Occiput with sinuate or incomplete row of spinules; Abdominal terga without spinules. | |
| 2a. Occiput with sinuate and irregularly spaced row of spinules; Abdominal terga with few or no intercalary spinules. |   |
| 2b. Occiput with few scattered spinules near the post ocular fringe; Cerci with long fringe of silky setae.
Only a few scattered spinules behind the eyes. The longer setae (hairs) by the eye are the "postocular fringe". All our perlids have a postocular fringe so its not useful for separating the species. |
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