Cycles biologiques d'Elmidae (Coléoptères) de ruisseaux des Laurentides, Québec

Abstract

1. Five stream-dwelling elmid species were studied and each lives in a particular substratum: Stenelmis crenata on sandy bottoms, Optioserous ampliatus within gravel, Macronychus glabratus on submerged decaying wood, Promoresia tardella among aquatic mosses and Oulimnius latiusculus in mixtures of gravel and sand.2. All are microphagous and eat decaying vegetable materials (30-90%) and diatoms (10-70%).3. The numbers of larval instars differ from species to species: 8 instars for S. crenata, 7 for O. ampliatus, 6 for M. glabratus and P. tardella, and 5 for O. latiusculus.4. The more useful characters for the identification of the instars are the length of the prothorax or the 9th abdominal segment and the cuticular features.5. The life cycle of the species seems to last at least three years and perhaps four for S. crenata, two of which as larvae (three for S. crenata) and one as adults.6. Eggs are laid during mid-summer and most hatch in August.7. The first year, the larvae develop to the instar III and overwinter at this stadium as growth is stopped or extremely reduced at 0 °C.8. The larvae complete their growth during the summer of the second year and overwinter again as last instar larvae.9. In the next spring, these last instar larvae leave the water and pupate under debris along the banks between June and August.10. Adults emerge in August, but have to wait for the following summer before mating and ovipositing. © 1976 Masson.