Seasonal Occurrence of Different Grasshoppers Species (Orthoptera: Acridoidea) in Uruguay

This paper aims at knowing the seasonal occurrence of grasshoppers (Orthoptera: Acridoidea) in Uruguay. The populations of these native herbivores are generally in equilibrium, although population increases were recorded under certain conditions, causing significant economic loss. The population was monitored during five seasons on sites located in the departments of Florida and Durazno. The insects were categorized into young nymphs (I, II and III), older nymphs (IV and V), and adults. At each sampling time, data from the different sites were grouped to calculate the percentage of each category. Twenty-six species were collected, eight of which were abundant. Borellia bruneri (Rehn, 1906), B. pallida (Bruner, 1900), Dichroplus pratensis Bruner, 1900 and D. elongatus Giglio-Tos, 1894 proved to be univoltine. More than one generation of Baeacris pseudopunctulatus (Ronderos, 1964), Orphulella punctata (De Geer, 1773), Scotussa lemniscata (Stal, 1861) and D. conspersus Bruner, 1900, was recorded per year in some seasons. The first births of B. bruneri, B. pallida, D. pratensis, D. conspersus, S. lemniscata and B. pseudopunctulatus occurred in October, whereas for D. elongatus and O. punctata they happened in November. Considering the eight species, young and older nymphs predominated until early December and from late December to early January, respectively. Adulthood was predominant since the end of January. These results are the basis for establishing a monitoring plan. In order to determine the need for control and to avoid irreparable loss, samples must be intensified from early November to the beginning of December, when the young nymphs are no longer predominant.