Life history of two burrowing aquatic insects in southern Europe: Leuctra geniculata (Insecta: Plecoptera) and Ephemera danica (Insecta: Ephemeroptera)

Burrowing is a common behavioural adaptation of lotic freshwater invertebrates to avoid the effects of current. This behaviour is accompanied by morphological adaptations. This also applies to the larvae of the stonetly Leuctra geniculata (Stephens, 1836) and the mayfly Ephemera danica Muller, 1764, both colonising habitats within the substrate and adapted to barrow in it. We have studied their life cycles and their relation with water temperature and day-degrees, feeding and secondary production. The stonefly had a univoltine life cycle with a larval development of 8 months and with an egg incubation period longer than previously reported. The possibility of an egg diapause stage is discussed. The mayfly was semivoltine. completing its larval development in 22 months. Both species mainly fed on detritus, but also ingested a high quantity of CPOM and some other minor components. Annual secondary production in both species was relatively high, being higher in the stonefly.