Morphometry, development, and food acceptance in Cornops aquaticum (Acrididae: Leptysminae) from Argentina

FRANCESCHINI M.C. & S. CAPELLO.

Recife Pernambuco

Simposio; Simposio sobre Conocimiento de Orthoptera no Brasil: estado atual e perspectivas para o futuro.; 2006

XXI Congresso Brasileiro de Entomologia

Cornops aquaticum Bruner (1906) is widely distributed in Latin America and has its life cycle associated with Pontederiaceae, in particular the waterhyacinth Eichhornia crassipes and E. azurea. Determination and identification of immature stages are needed to study population structures in a specific region. Food tests in nymphs and adults are important as this grasshopper is considered a possible biological control agent of the waterhyacinth, an introduced pest on artificial and natural water bodies around the world. The purpose of this study was (i) to evaluate which morphometric characters can be used to define immature stages; (ii) to determine the number of nymphal instars under different conditions of temperature and insolation;(iii) to compare food acceptance of nymphs and adults on vegetables and on macrophytes coexisting with E. azurea and E. crassipes. First-stage nymphs were reared at two localities (Corrientes: n=29, 28, 24;Santa Fe: n=26, 16). Morphometric characters taken were: length from fastigium to end of tegmina (A),length from fastigium to end of abdomen (B), length of hind femur (H), fresh weight, length of antenna (L), and number of antennal segments. Length of the hind femur (H) was the most constant and precise character in each nymphal instar, subject to little measuring bias and easy to obtain when working with high population densities. The number of developmental stages depended on sex, with male nymphs having five and female nymphs five or six instars. Food tests with about fifteen different macrophyte and vegetable species offered to 30 nymphs on each plant species during 12 days showed that survival was highest on E. azurea and E. crassipes