Phenology of Cornops aquaticum Bruner (Orthoptera: Acrididae) on Eichhornia crassipes floating meadows in a wetlands of the Paraná River Floodplain (Argentina).

FRANCESCHINI M.C., J. ADIS, & A. POI DE NEIFF.

Cuiabá, Mato Grosso (Brasil)

Conferencia; 8th INTECOL International Wetlands Conference; 2008

International Association for Ecology, Universidade Federal de MAto Grosso, Centro de Pesquisa do Pantanal.

Cornops aquaticum Bruner is a native Latin-American grasshopper frequently associated with the Pontederiaceae, primarily with the water hyacinth, Eichhornia crassipes (Mart.) Solms. This macrophyte, which is native to South America, has been introduced in several countries, and is spreading at an alarming rate. It has become the most important pest species of natural and artificial water bodies around the world. C. aquaticum is being intensely studied for the possible release in South Africa as a biological control agent of E. crassipes. The aim of this research was to determine the age structure of C. aquaticum populations in a wetland located in the Paraná River floodplain (Argentina), where E. crassipes represented the only host plant. Between February 2004 and April 2006 monthly samples were taken with a net of 70 cm in diameter. We quantified the relative abundance of adults, nymphs A (stage I and II) and nymphs B (stages III to VI) and colorations of individuals. Ovary maturation and the opening and closing of the ovipositor valves were registered in females. Adults were found in all sampling dates whereas nymphs A were absent during the coldest months. During the spring summer periods, the major proportion of nymphs A was coincident with the major proportion of females with mature ovaries and open ovipositor valves. Adults and nymphs B were green during the spring-summer period, and during the cold months they changed color, becoming brown. The results suggest that C. aquaticum showed different reproduction periods and had different colour morphs during the study period.