The first antennal segment equal to or longer than succeeding 6 segments together; labium (ligula) with a deep, open, median cleft. Labium cleft only to base of palpal lobes. Gills long and slender with many thin marginal hairs, but no stiff setae along the gill margins; common statewide on shady streams. Median gill without stout spines, only thin, short setae and few long hair-like setae along margins; no stout spines on posterior portion of lateral carinae of sbdominal segments 9 and 10. Very early instars of Calopteryx maculata and the similar Calopteryx aequabilis were distinguishable based on the head width and length of the proximal antennal segment. In C. maculata, the length of antennal segment 1 is approximately 0.85x than the width of the head across eyes; while the tubercles behind the eyes are prominent and acute, raised above the level of eyes; and the hind femur of the final instar larva is 7.5 mm or less. In C. aequabilis, the length of antennal segment 1 is approximately 0.95x or greater than the width of the head across eyes; while the tubercles behind eyes are low and rounded, not raised above level of eyes; and the hind femur of the final instar larva is 8.2 mm or more (Martin, 1939).
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