Partial bivoltinism and emergence patterns in the North African endemic damselfly Calopteryx exul: conservation implications

Calopteryx exul is an endemic endangered damselfly that suffers considerable habitat degradation and local extinctions throughout its geographic range. Although recent studies have investigated its distribution, ecology and larval systematics, the life history of the species is still unknown. In this study, a field survey was conducted to determine larval development, temporal pattern of emergence and teneral spatial distribution of the species in the Seybouse watershed, north-east Algeria. Larval growth was investigated in two populations: one at about 200 m (low-elevation population) and the second at 600 m of elevation (high-elevation population). The species showed partial bivoltine life cycle in both low- and high-elevation population. The temporal pattern of emergence of the first flight season of the year at low-elevation population was asynchronous with an emergence season lasting 46 days and half of the population emerging in 15 days. The second flight season was shorter with a most likely smaller population size. Sex ratio at emergence was slightly male biased. After ecdysis, tenerals stayed next to the water within a mean distance of 4.76 ±4.35 m (±SD) with no significant difference between sexes. Conservation measures that should be taken into account in the elaboration of future management plans for the species are discussed.