| 1a |
Finely branched gills behind bases of legs |
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| 1b | Gills absent behind bases of legs | {continue line 3} |
| 2a | Finely branched gill tufts originating from basal abdominal segments 1 and 2. | Pteryonarcyidae |
| 2b | Gill tufts never on abdomen | |
| 3a | On underside of head, body of labium (ìlower lipî) compact with tips of glossae extending nearly as far forward as tips of paraglossae |
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| 3b |
Body of labium divided into 2 with tips of glossae located far behind tips of paraglossae |
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| 4a | Abdomen divided by a membraneous fold along its whole length, middle segments of abdomen, when viewed from above, are wider than the base of the terminal segments, body is usually brown in colour |
Capniidae |
| 4b | Abdomen divided by a membraneous fold along no more than the first 6 segments, sides of abdomen more or less parallel down their length, usually pale in colour |
|
| 5a | Thoracic wing pads divergent, tails are at least as long as abdomen, and hind legs as long or longer than abdomen, thorax and head usually with a distinct dark and light colour pattern |
|
| 5b | Thoracic wing pads parallel; tails <3/4 length of abdomen, thorax and head usually without pattern |
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