Population dynamics of two species of Neochetina (Coleoptera: Curculionidae) associated with Eichhornia crassipes (Pontederiaceae), in oxbow lakes of the Pantanal wetland (Mato Grosso, Brazil)

The dynamics population of Neochetina eichhorniae Warner, 1970 and Neochetina bruchi Hustache, 1926 (Coleoptera, Curculionidae) was studied in five oxbow lakes along the Cuiaba River, Pantanal of Barao de Melgaco - MT, during one hydrological cycle, from December 2005 to November 2006. A total of 1,871 (78.45%) adult individuals and 514 (21.55%) immature individuals were sampled. The abundance of adults sampled for the two species, considering all sites, differs significantly in comparison with that of immatures, ranging along the hydrological cycle studied. The proportion of immatures was similar to adults only during the flooding period. The population of adults of N. eichhorniae, considering all sites, was significantly higher than that of N. bruchi, varying over time. The maximum abundance of adults occurred during the high and low water period to N. eichhorniae, and in low water and beginning of the dry period for N. bruchi. The variation in abundance, for the development phase during the year assessed can be explained according to the variation of the relative frequency of the host plant, Eichhornia crassipes (Mart.) Solms (Pontederiaceae), the most common and abundant aquatic macrophyte in oxbow lakes sampled along the hydrological cycle studied.