Cycles de développement de quelques invertébrés benthiques dans des ruisseaux des Pyrénées centrales

Abstract

1. The life-cycles of 14 species of benthic invertebrates were studied in three small streams at a mean altitude (732 m) in the central Pyrenees. 2. The temperature stays fairly constant throughout the year (minimum 8.5° C in February; maximum 13° C in August and September). 3. The different size classes or larval stages were determined by observing the wing buds (Ephemeroptera) or by measuring the width of the head capsule (Plecoptera, Trichoptera, Coleoptera). 4. The periods of emergence and hatching were generally longer or shorter than those reported by other workers. The temperature conditions caused a regular growth in the fauna. 5. The life-cycles were classifled on the basis of the length of the hatching period and adult life, and were compared by the classification of Hynes (1961-1970).A new type of development (S4) was found for a species with slow growth and an autumnal flight period. The juxtaposition of several factors seemed necessary to distinguish the larval development of certain species in which hatching continued for a long time. © 1971 Masson.