N. pentacantha was reared in the laboratory from egg to adult in one year, and had 14 or 15 larval instars. Instar 2 differs from all other Nearctic Aeshnidae by having 2 pairs of horns on the head. Instars 3-15'differ from all other Nearctic Aeshnidae by having mid-dorsal abdominal spines on at least segments 8 and 9. Stadia duration decreases from instars 2 to 4, then increases to 7, then decreases at 8, then increases to possible diapause in late instars. Male larvae died at a faster rate than females (p <0.01), so that by instar 15 only 37.5% of the survivors were males. Growth rates for both head width and total body length varied cyclically, with maxima at instars 4, 9, and 15 and minima at instars 2, 6, and 12. Certain morphological changes between instars are described.