hide
Free keywords:
Hemimetabolous metamorphosis; instar distinction; pterothecae; stoneflies; biometry
Abstract:
Wing development in Plecoptera was expressed by a wing index: wingpad length/head width. Wingpads develop in the last three larval instars which each extend over a large size range. Characteristic shapes permitting accurate instar identification in life history and ecological studies are illustrated. Instar distinction fails in the broad-bodied Perlidae and Peltoperlidae. Only the lasat instar of Pteronarcys (Pteronarcyidae) is dinstinct, probably because of flexible moulting during the long life cycle. Wingpads are separated from the notum by folds or notches, except in Peltoperlidae and in Perloidea where wingpads are partly to entirely fused to the notum, apparently convergently.
