| 1a. Cervical gills present |  |
| 1b. Cervical gills absent | |
| 2a. Cervical gills with 5 or more branches. Femora plain, no setae. | |
| 2b. Four simple cervical gills or gills with 4 or fewer branches. Legs with band of setae around femora of legs.
The setae on the backs of their legs is visible on very small nymphs and on the animal at the right. |
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| 3a. Cervical gills branch from a basal trunk. Most of gills are about the same length with a few shorter gills on the outside of the neck. Gills do not branch secondarily. | |
| 3b. Some cervical gills branch midway out their length. Gills branch palmately from base. Gills vary in length.
(Some gills have a Y-shape) |
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| 4a. A fringe of long hairs on the outer margin of the foretibia. | |
| 4b. No fringe on foretibia although a few long hairs may be present. |