Systems of the chalcid wasp (Hymenoptera, Chalcidoidea) adaptations to parasitizing soft scale insects (Homoptera, Coccidae) in principal climatic zones of the Northern Hemisphere

摘要

The evolution of systems of adaptation of chalcid wasps to parasitizing soft scale insects follows different directions in the tropics, temperate zone, and the Hypoarctic zone. These zones have different biotas and are characterized by different modes of seasonal development of hosts: polycyclism, monocyclism, and hemicyclism, respectively. The main feature of the polycyclic development is the overlapping of generations, which maintains a relatively constant mixed-age structure of a host population; whereas the monocyclic and hemicyclic seasonal types are characterized by separate development of host stages and instars during one or two seasons. Thus, the mode of seasonal development, combined with the high specific diversity, high level of competition, and fragmentation of resources, determines the evolution of characterislic trophic links of chalcids in tire tropics. Their main feature is habitat preference: in a particular habitat, a parasitic female infests hosts of all ages, or only of somespecific age group, but within a very wide taxonomic range. Under these conditions, the "preemptive" strategy of parasitization has arisen, with a trend toward infestation of younger stages (instars) of hosts. This strategy is most pronounced in a specific guild of chalcidoid parasites, unknown in the temperate zone and characterized by infesting only 1st instar nymphs of hosts. The morphological adaptations of adults ensure a moderately long adult lifespan, sufficient for host-seeking and successful reproduction. In the temperate zone and the Hypoarctic zone, where the host species diversity decreases from low to high latitudes, with different stages of a host becoming more separated during a season, chalcid wasps commonly show high host specificity and complicated seasonal cycles. In these zones, chalcids have developed two main strategies of parasitization, which help them survive the hostless period and ensure the optimal encounter of a mature parasite female with a host of a definite infestable stage (instar). The survival strategy is characterized by prolonged lifespan (covering about a year) of comparatively large- sized adult females. By contrast, the evasion strategy is characterized by an ephemerized adult and relatively long preimaginal stages.