Neotropical Entomology (2007) 36, 495-502

Jorge Cepeda-Pizarro, Solange Vega, Hernán Vásquez, Mario Elgueta and Jaime Pizarro-Araya (2007)
Demographic study of two population outbreaks of Elasmoderus wagenknechti (Liebermann) (Orthoptera: Tristiridae) in the transitional desert of Chile
Neotropical Entomology 36 (4), 495-502
Abstract: Under certain environmental conditions, several species of grasshoppers inhabiting rangeland areas (e.g., inter-valleys) of the Chilean transitional desert can errupt demographically. One of them is Elasmoderus wagenknechti (Liebermann), an endemic species. We studied two outbreaks occurred in 1996 and 1999. The objectives of the research were to (i) estimate some demographic parameters associated with the aforementioned events, and (ii) compare between them the population parameters. The parameters we studied were density (ind/m²), sexual proportion, female fertility (i.e., eggs/female), and the relationship eggs/female versus female size. Density (ind/m²) ranged from 0.2 to 0.4 in 1996 and from 0.5 to 0.6 in 1999. ANOVA-tests registered differences in density among study sites and between years. In some of the study sites, females were more abundant than males (e.g., Lomas del Sauce). Females fertility ranged from 27 to 39 eggs per female, with significant differences among sites in 1996 but not in 1999. For females of 30-50 mm body size, a linear relationship was detected between egg number/female and body size. It is concluded that the E. wagenknechti outbreaks are site-specific in the study area and that the demographic parameters examined show a high variability among sites and between events.
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Research topic(s) for pests/diseases/weeds:
population dynamics/ epidemiology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Elasmoderus wagenknechti	Grasses/turf/rangeland	Chile (continental)