Are two cohorts responsible for the bimodal life-history pattern in the wolf spider Pardosa agrestis in Hungary?

Wolf spider species of the genus Pardosa show a typical stenochronous life cycle, adults reproducing in the spring and different instars of the juvenile stage overwintering (Schaefer, 1977). The life cycle is typically one year long (Tretzel, 1954; Vlijm et al., 1963; Merrett, 1968) in Western and Central Europe, but at more Northern latitudes it can be extended to two (Edgar, 1972; Stepczak, 1975) or three (Workman, 1979) years, with no change in the season of the reproductive period. In Hungary one Pardosa species, P. agrestis, has received special attention, because it can be regarded as the most dominant surface-active spider in every agricultural or human-influenced habitat (Samu et al., 1996; Tóth et al., 1996). A large amount of data has been collected on this species by the authors over three years, from numerous localities, as part of a nationwide survey on the spider diversity in agroecosystems. Examining the individual datasets of the adult specimens, it was obvious that the phenology of P. agrestis was different from the typical Pardosa life cycle, but we were unable to draw direct conclusions about its exact pattern. In the present study, to obtain a more complete picture of the life cycle of P. agrestis, we merged data from the different sites and attempted to work out methods which would allow us to incorporate data on different stages Are two cohorts responsible for the bimodal life-history pattern in the wolf spider Pardosa agrestis in Hungary?