Effect of Temperature and Interrelationships of the Host Pleuroptya ruralis, Its Primary and Secondary Parasitoids in Lithuania

Abstract

Research results on the long-term dynamics (1982-2004) of the temporal dispersion of the host Pleuroptya ruralis, its parasitoid the Macrocentrus cingulum as well as its second parasitoids Encrateola laevigata, Gelis ruficornis and Pteromalus dispar on common nettle in Lithuania and the relationships between the air temperatures and development of these species are presented. Multiple regression analysis was carried out to determine the most important relations between dependent (appearance date, emergence peak, adult emergence duration, density) and some independent variables (air temperature, life cycle parameters of related species). The most important factors for the life cycle parameters of investigated species were determined.

The appearance dates and the emergence peaks of secondary parasitoids Encrateola laevigata, Gelis ruficornis and Pteromalus dispar are related with air temperature in June and the appearance date of their host M. cingulum. The appearance date as well as the emergence peak of P. ruralis are the most important factors for the appearance date and the emergence peak of M. cingulum. The most important factors for the emergence durations of secondary parasitoids are their densities. The emergence duration of P. dispar is related with air temperature in July and the emergence duration of M. cingulum, which is related with the emergence duration of its host. Densities of the secondary parasitoids were related with density of primary parasitoid, which was influenced by the density of the host, P. ruralis.