A major issue for the proper understanding of the evolution of life-cycle histories is the regulation of voltinism and its variation. Diapause characteristics are known to regulate voltinism, but the underlying mechanisms are poorly understood. This paper studies diapause duration and voltinism variation in a haematophagous diptera parasitizing 2 sympatric hosts with very different breeding phenologies. We hypothesize that bivoltinism will be more frequent in carnid flies parasitizing an early breeding, multi-brooded species than in flies parasitizing a late breeder, single-brooded species. We obtained evidence of the co-occurrence of uni- and bivoltinism in both clutches of the multi-brooded Spotless starling (Sturnus unicolor) as well as in clutches of the single-brooded European roller (Coracias garrulus). Unexpectedly, the proportion of bivoltine flies was similar in both host species. A remarkable degree of host-parasite synchronization at the population level was found for bivoltine flies. Our findings reveal the facultative nature of diapause in Carnus. We discuss the influence of abiotic conditions and host availability on polymorphism in life-history cycles and the consequences both for the parasite and the host.

The temporal dynamics in density, life histories, and emergence patterns were described for the first time for five Plecopteraspecies in tributaries of the Futaleufú River in Patagonia, Argentina. Benthic samples and adult collections were made in five loworder Nothofagus forested streams. Four species of Gripopterygidae; Aubertoperla illiesi, Notoperlopsis femina, Antarctoperlamichaelseni and Senzilloides panguipulli had simple, highly synchronized univoltine life histories. The austroperlid Klapopteryxkuscheli takes more than two years to develop. Emergence periods of most of the species were concentrated in late spring andsummer (October to February), which suggests seasonal and synchronized life histories. Most N. femina adults were collected inmid spring indicating this species emerged first, whereas S. panguipulli emerged last from January to April. Aubertoperla illiesishowed a slightly delayed emergence at the high elevation site (La Hoya Stream) when compared to a piedmont stream,suggesting that temperature was an important control. Although we were unable to describe the life history of Limnoperla jaffueli(Gripopterygidae) its adult emergence period was November to January. Life histories of Plecoptera species in the studiedstreams seem to have a high degree of seasonality at least at this latitude, and are possibly determined by predictable temperaturepatterns and discharge regimes. This first contribution on the life histories of Plecoptera species helps us to better understand thedynamics and functioning of pristine but fragile aquatic environments in Patagonia.