The life cycle of Argia vivida Hagen: developmental types, growth ratios and instar identification (Zygoptera: Coenagrionidae)

Eggs were hatched in the laboratory and larvae reared to the final instar. Three developmental types were recognized (12, 13 and 14 instars) and there was a positive correlation between growth rate, final size, number of instars and temperature between 15 and 25° C. These factors, plus intra-instar variation, allow only the 1st, 2nd, 3rd, and final instars to be identified with certainty. The number of antennomeres, metathoracic wing pad length, and head width were useful in assigning larvae to instar. Head width growth ratios decreased as larvae grew; the average growth ratio was 1.24.