Larval development and ecology of Baetis liebenauae Keffermuller (Ephemeroptera: Baetidae) in a north Italian lowland spring

The life cycle of Baetis liebenauae has been investigated in a lowland spring of Northern Italy that shows a relative stability of water temperature. Nine postlarvula morphological stages of the larva were identified and a ''jump development'' of the wing-pads between stage pairs has been noted. B. liebenauae is here a typical polyvoltine species and three generations can be defined, with the late-summer/autumn generation being the main one. During this generation the species is often the dominant taxon of the benthic community and shows a high larval density. Marquet differences have been in comparison noted with the development of this species in Poland. This is probably due to the different thermal features of the two regions. A temporal shift of the main generations seems to allow the coexistence of B. liebenauae and other high density Baetidae species. In Southern Europe the species is typical of small lowland streams with slow flowing waters. Its larvae live on aquatic macrophytes and their presence on mineral substrata can be considered as occasional.