Dichroplus maculipennis and Borellia bruneri are two of the 18 grasshopper species of actual or potential economic relevance as pests in Argentina. The objective of this study was to estimate the sex ratios for adults and older nymphs of D. maculipennis and B. bruneri in the field, and analyze possible temporal variations. The study was conducted during seven seasons (2005-06 to 2011-12) in representative plant communities of the southern Pampas region. A total of 4536 individuals of D. maculipennis, and 6038 individuals of B. bruneri were collected. The sex ratio registered in older nymphs for D. maculipennis and B. bruneri did not deviate from a 1:1 ratio (p > 0.05), suggesting that these species have such a primary sex ratio. However, a significant bias in sex composition in adults of both species was observed (p < 0.05). The sex ratio in adults of D. maculipennis was different in five of the 18 sampling dates carried out. In three sampling dates it was biased toward males, while in the other two it was biased toward females. Taking into account the sex ratio by sampling season, significant differences were recorded in two seasons. In 2007-08 the sex ratio was biased toward males (1 F:2.26 M), while in 2008-09 it was biased toward females (1.35 F:1 M). The sex ratio in adults of B. bruneri was always biased toward males (p < 0.05). We conclude that results obtained in this study indicate that various factors like differential survival, dispersion, predation, among others, could have modified the primary sex ratio in these species.

Five cohorts of Baeacris pseudopunctulatus Ronderos were monitored under controlled conditions (30º C, 14L:10D, 40% RH) in order to determine some fundamental aspects of its biology and reproduction. Five nymphal instars were recorded. The observed developmental time in nymphs was 30,14 ± 0,85 days. Mean duration of cohorts was 10,66 ± 1,7 weeks. Mean number of egg-pods per female was 3,56 ± 0,52, and mean number of eggs per pod was 15,5 ± 0,6, with a minimum of 10 and a maximum of 22. Mean fecundity (number of eggs per female) was 46,03 ± 6,84. The egg-laying rate was 1,20 ± 0,21 eggs/female/day.

Se realizó el seguimiento en laboratorio de cinco cohortes de Baeacris pseudopunctulatus Ronderos, con el objetivo de conocer algunos aspectos fundamentales su biología y reproducción bajo condiciones controladas (30º C, 14L: 10O, 40% HR). Se registraron 5 estadios ninfales. La duración del ciclo ninfal fue de 30,14 ± 0,85 días. La duración promedio de las cohortes fue de 10,66 ± 1,7 semanas. El número promedio de posturas por hembra fue de 3,56 ± 0,52. El número promedio de huevos por postura fue de 15,5 ± 0,6, con un mínimo de 10 huevos y un máximo de 22. La fecundidad promedio (número de huevos/hembra) fue de 46,03 ± 6,84. La tasa de oviposición fue de 1,20 ± 0,21 huevos/hembra/día.

First generation cohorts obtained in the laboratory from field collected (southeast of San Luis province) individuals of the grasshopper Ronderosia bergi (Stål), were used to measure some developmental parameters of the species under controlled conditions (30 ° C, 40% RH, 14 hs. L: 10 hs. D). The total duration of the postembryonic development was 213 days, of which thirty were devoted to the five instars of nymphal development. The mean number of eggs per eggpod was 16.8, and sexual maturity was reached 4-5 days after the last molt. Differences with data coming from other studies may be due to the different conditions used or the high intraspecific variability of R. bergi.

Mediante el seguimiento de cohortes correspondientes a la primera generación de bioterio, provenientes de ejemplares capturados en el sudeste de la provincia de San Luis, se registraron algunos parámetros biológicos fundamentales del acridio Ronderosia bergi (Stål) bajo condiciones controladas (30 ° C, 40% HR; 14hs. luz, 10 hs. oscuridad). La duración total del desarrollo postembrionario fue de 213 días, de los cuales 30 correspondieron a los cinco estadios del desarrollo ninfal. El número promedio de huevos por postura fue de 16,8, y la madurez sexual fue alcanzada dentro de los 4-5 días después del ingreso a imago. Las diferencias con los escasos datos provenientes de estudios previos, obedecerían a las distintas condiciones de crianza o a una alta variabilidad intraespecífica.