Los acridios (Orthoptera: Caelifera: Acridoidea) son insectos nativos que habitan pastizales en Uruguay. En ciertas ocasiones incrementan la abundancia exponencialmente, como en los años 1950´ y en 2008/09, causando importantes pérdidas económicas. Este trabajo tuvo como objetivo describir la variación interanual de la abundancia y diversidad de las comunidades que habitan pastizales de la región centro-sur. El seguimiento de las poblaciones se realizó durante cinco temporadas, en sitios de Florida y Durazno. Se estimaron: riqueza acumulada y específica por sitio (S), índices de diversidad de Shannon-Weiner (H´), equitatividad de Pielou (J´), similitud cualitativa de Sorensen (Is), constancia de presencia (C), y abundancia total (A), específica absoluta y relativa. A través de las variaciones temporales de dichos descriptores comunitarios se identificaron y caracterizaron períodos de explosión poblacional, transición y equilibrio. En 2009/10 (explosión poblacional) S, A, e Is fueron máximos, J’ y H’ bajos y Borellia bruneri (Rehn, 1906) fue la más abundante. El período 2010/11-2011/12 (transición), se caracterizó porque J´ e Is fueron intermedias, A y S bajas, y continuó el predominio de B. bruneri. Durante 2012/13 y 2013/14 (equilibrio), se registraron los más altos J´ y H´, y la abundancia relativa de B. bruneri disminuyó significativamente. En este período Scotussa lemniscata (Stål, 1861) fue predominante. Los resultados obtenidos indican que en pastizales de la región centro-sur del Uruguay, el predominio de B. bruneri, la disminución en J´ y el aumento de Is serían indicadores de un período de transición hacia una explosión poblacional.

Acridians (Orthoptera: Caelifera: Acrididae) are native insects that inhabit Uruguayan grasslands. Occasionally, abundance increases exponentially, as in the 1950' and in 2008/09, causing significant economic losses. This work aimed to describe the variation in the abundance and diversity of the communities that inhabit the grasslands of south-central region. Acridian populations were monitored during five seasons in Florida and Durazno sites. Cumulative and site-specific (S) richness, Shannon-Weiner (H ‘) diversity index, Pielou evenness (J’), qualitative similarity of Sorensen (Is), constance of presence (C), total abundance (A), and absolute and relative specific abundance were estimated. Based on these community descriptors and their temporal variations, we identified and characterized outbreak, transition and non-outbreak periods. In 2009/10 (outbreak) S, A, and Is, were highest, J ‘ and H’ were low, and Borellia bruneri (Rehn, 1906) was the most abundant species. The 2010/11 -2011/12 period (transition), was characterized by intermediate J’ and Is, low A and S, and B. bruneri remained predominant. During 2012/13 and 2013/14 (equilibrium), higher values of J ‘and H’, and low values of A, S and Is were recorded, and the relative abundance of B. bruneri decreased significantly. In this period Scotussa lemniscata (Stål, 1861) was the predominant species. These results indicate that in the grasslands of south-central region of Uruguay, the prevalence of B. bruneri, the decrease in J’ and increase in Is, would be indicators of a transition period to an outbreak.

En la primavera del año 2008 en la región centro-sur del Uruguay se registró un importante incremento en la población de Borellia bruneri que no se registraba desde hacía 50 años. El momento adecuado de realizar tratamientos para evitar daños es cuando la mayor proporción de la población se encuentra en el estadio de ninfa tres, así la eclosión de huevos es máxima, y se evita el momento de mayor consumo y de disminución en la sensibilidad a los insecticidas. Este trabajo fue realizado en 2009-2010 para conocer el ciclo y la fenología de esta especie en un pastizal natural en el departamento de Florida, Uruguay (33º45’9.30"S 55º54’11.90"O). Desde principios de octubre hasta mediados de enero se realizaron muestreos semanales, y luego muestreos quincenales hasta el fin del período a fines de abril. Los estadios ninfales se determinaron según el desarrollo de los rudimentos alares, la genitalia externa y el número de segmentos antenales. Complementariamente se realizó un estudio morfométrico para caracterizar los estadios previamente diferenciados por las características morfológicas. Se determinaron cinco estadios ninfales fácilmente distinguibles en base al desarrollo de los rudimentos alares y la genitalia externa. Largo de la cabeza, diámetro mayor del ojo y largo del fémur posterior fueron los caracteres más útiles para separar los individuos de los distintos estadios del mismo sexo y entre sexos. Esta información tiene utilidad para planificar estrategias de control oportunas sin que ocurran daños irreparables durante explosiones poblacionales de esta especie

In the spring of 2008 in the central-south region of Uruguay, there was a significant increase in the population density of Borrellia bruneri not witnessed for 50 years. The proper time for treatments to prevent damage is when the highest proportion of the population is in nymph III, so hatching eggs is maximum, and avoiding the peak of consumption and the decrease in sensitivity to insecticides. This work was conducted in 2009-2010 and aimed to identify the cycle and phenology of this species in a natural grassland located in Florida, Uruguay (33º 45' 9.30" S 55º54’11.90" O). From early October to mid January we conducted weekly sampling, and then biweekly until the end of the period in late April. The nymphal stages were determined according to the development of wing rudiments, external genitalia and the number of antennal segments. Additionally a morphometric study was performed to characterize the instars previously differentiated by morphological characters. Five easily distinguishable nymphal instars were determined, based on the development of the wing pads and external genitalia. Head length, the larger diameter of the eye, and length of the hind femur were the most useful characters to separate individuals of different nymphal instars of the same sex and between sexes. This information is useful for planning timely control strategies without irreparable damage during population explosions of this kind

The acoustic behavior of Fenestra bohlsii Giglio-Tos is described for the first time. The sounds and behaviors were observed and registered in captivity. The signals were digitized with the Sound-Blaster AWE64 Gold program and analysed with the Avisoft SAS Lab Pro 30 PC for MS Windows software. Seven different types of sounds are described as produced by males: spontaneous song (also used during the courtship), two different types of courtship song, assault song, tapping associated to the courtship, interaction between males and fly crackling. For each one, the characteristic oscillograms and frequency spectra are given. Sounds are produced by different mechanisms: femoro-tegminal stridulation, typical for Gomphocerinae, fly crackling, hind tarsi tapping and alar beat, the last produced by the beat and clash of hind alae, that is, the castanet method which up to now was only known, among Orthoptera, in Stenobothrus rubicundulus Kruseman & Jeekel. A description of the stridulatory file of male and female is given, as well as that of the alar special structures. Behavioral units and their sequence during the courtship are defined. There, in addition to the acoustic signals, visual signals are present, referring to positions, hind legs, antennae and palpi movements and body vibrations.