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

Estrellita Lorier,Lucia Miguel,Maria Stella Zerbino

doi:10.5539/ijb.v8n4p21

Abstract

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.

Highlights

Grasshoppers (Orthoptera: Acridoidea) are native herbivores that inhabit the grasslands of Uruguay, being a characteristic assemblage of this ecosystem (Lorier et al, 2010)
The abundance of all species decreased significantly in the remaining seasons, in the case of O. punctata, D. conspersus and D. elongatus, of which less than 45 specimens of each species were collected throughout the four ensuing seasons (Table 2).There were some variations between seasons at the time each category was recorded (Figure 2a-h)
Older nymphs of B. bruneri were first recorded in November-1, while those of B. pallida, and D. pratensis were collected since November-2 (Table 3, Figure 2a, b, and f)

Summary

Introduction

Grasshoppers (Orthoptera: Acridoidea) are native herbivores that inhabit the grasslands of Uruguay, being a characteristic assemblage of this ecosystem (Lorier et al, 2010). Their population dynamics is highly variable; responses are non-linear, and they result from the combined effects of abiotic factors (weather) and biotic interactions (competition, predation, parasitism) (Joern, 2000). In Uruguay, significant problems with grasshoppers were recorded in the 1950s and recently in the spring-summer of 2008/09 (Lorier & Zerbino, 2009). In the outbreak of 2008/2009, damage from Scotussa lemniscata (Stål, 1861) and Baeacris pseudopunctulatus (Ronderos, 1964) was observed (Carbonell 1957, 1995; Lorier et al, 2010)

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Discussion

Conclusion