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Abstract

Várzea floodplains in Central Amazonia are exposed to annual cyclical oscillations in river water levels, between the high and low water periods. The high water period can last five to seven months. This hydrological dynamic forces plants and animals to develop adaptive strategies in order to survive. The predacious grasshopper Phlugis teres (DE GEER, 1927) lives its cycle on aquatic macrophytes that offer nutritional resources and oviposition sites. On floating "meadows" of Eichhornia crassipes a total of 583 P. teres were collected on the Solimões river near Manaus, Amazonas, during rising, high, and falling water periods (47,2% adults (166♂♂ e 142♀♀) and 52.8% nymphs). This represents a total dry weight biomass of 6.4 g (81.7% for adults, 18,3% for nymphs). Average grasshopper abundance varied between 2.6 ind./m² and 9.6 ind./m²; dry weight biomass was 0.1 g/m². The abundance and body size of the arthropods (especially of Acari, Hemiptera, Homoptera and Collembola) that lived associated with this aquatic macrophyte or utilized it temporarily as habitat during the high water period, were correlated with the abundance and body size (developmental stage) of P. teres, indicating their potential importance as prey items. Nymphs were present during the entire sampling period, but adults were more abundant during the falling water period. During the low water period of the Solimões river E. crassipes disappeared in the study area, and P. teres was found on other species of aquatic macrophytes and in the canopy of trees.