Larval development and growth ratio in Ischnura cruzi De Marmels, with description of last larval instar (Zygoptera: Coenagrionidae)

Under stable laboratory conditions larval stages were measured and morphologically compared in order to establish growth ratio and total number of instars through their postembryonic development. Head width, total length, metafemur length, forewing pad length, and length and width of premenlum were measured to determine variation between instars, and growth ratio was calculated. By Dyar’s Law, 12 larval instars were estimated. Fundamental morphological differences were found in order to distinguish the stages and at the same time to have a record of the morphological development through the stages. Finally, the last larval instar is described and illustrated.