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Morphometry; juveniles; nymphal stages; floodplains; Acrididae; Leptysminae; Cornops
Abstract:
Cornops aquaticum is a widely distributed species in Latin America and has a life cycle associated with Eichhornia crassipes (MART.) SOLMS and E. azurea (SW.) KUNTH (Pontederiaceae). The correct determination of the nymphal stages in C. aquaticum is important to study the population structure in a specific region. The purpose of this study is to evaluate if morphometric characters can be used to determine the different nymphal stages in C. aquaticum. For this reason, first-stage nymphs were reared at two localities (Corrientes: N = 29, 28, 24; Santa Fe: N = 26, 16) under different conditions of temperature and insolation. After hatching and after each moult, fresh weight ("Peso") of nymphs was determined and measurements of the following morphometrical characters were taken: distance from fastigium to end of pterothecas or pronotum (A), distance from fastigium to end of abdomen (B), length of hind femur (H), length of antenna (L), and number of antennal segments (N Ant.). Length of the hind femur (H) was the most constant and precise character in each nymphal stage, subjected to little measuring bias and easy to measure when working with a high population density. Morphometrical and morphological data are expected to contribute to the ecological knowledge of this species.
