Key to Stonefly Nymphs

Couplet 2

First posted April 19, 2010 Last updated May 19, 2010

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Pteronarcyid nymphs have gills on abdominal sterna (belly side) 1 and 2, or 1, 2 and 3.  Abdominal sterna 1 is the first abdominal segment after the thorax.  Placing the nymph on it's back is the best way to see this feature.  Pteronarcyid nymphs also tend to be very dark in color, as opposed to Perlid nymphs which tend to be more patterned.  Color is not the best characteristic to use because color will change if the specimen is stored in alcohol.   Perlid nymphs do not have gills on abdominal sterna (belly side) 2 or 3.  Abdominal sterna 1 is the first abdominal segment after the thorax.  Placing the nymph on it's back is the best way to see this feature.  Perlid nymphs tend to be patterned, and Pteronarcyid nymphs are very dark in color.  Color is not the best characteristic to use because color will change if the specimen is stored in alcohol.
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