Toxic tasting: how capuchin monkeys avoid grasshoppers' chemical defenses.

Platyrrhines consume many species of arthropods in the order Orthoptera. Some species of orthopterans can produce chemical defenses that render them toxic or unpalatable and thus act as predator deterrents. These species include the stick grasshoppers (family Proscopiidae), which are widely distributed in the Caatinga biome in northeastern Brazil, which comprises part of the distribution of capuchin monkeys. Capuchin monkeys are omnivores and consume a wide variety of foods, including unpleasant-tasting, potentially toxic items, which they need to learn how to process. We describe the processing of stick grasshoppers (Stiphra sp.) by wild capuchin monkeys (Sapajus libidinosus) that live in Serra da Capivara National Park, Brazil, and compare how individuals of different age classes handle these potentially toxic food items. S. libidinosus predominantly avoided consuming the digestive tract, which contains toxic compounds, when feeding on stick grasshoppers. Immatures took longer than adults to process the stick grasshoppers, indicating that capuchins need to learn how to process the toxic digestive tract of these prey to avoid consuming it.

Evolutionary history and colonization patterns of the wing dimorphic grasshopper Dichroplus vittatus in two Argentinean biomes.

Quaternary climate oscillations and modification of the environment by humans have played an important role in shaping species distribution and genetic structure of modern species. Here, population genetic parameters were inferred from the analysis of 168 individuals belonging to 11 populations of the South American grasshopper, Dichroplus vittatus, distributed in two Argentinean Biomes (Grassland and Savanna), by sequencing a 543 bp of the mitochondrial COI gene. Overall, we detected considerable haplotype diversity and low nucleotide diversity. AMOVA analyses showed a significant degree of differentiation among Biomes and between populations. Two major mitochondrial lineages can be distinguished. The haplogroup containing the most common haplotype split 17,000 years BP while the haplogroup including the second most common haplotype has a divergence date of about 11,700 years. Approximate Bayesian Computation (ABC) analyses showed that the palaeodemographic scenario that best fitted our data is consistent with a hypothesis of divergence from an ancestral population and subsequent admixture with Grassland-Savanna (South-North) direction. Our results suggest that populations located in both Biomes would derive from a single ancestral population that colonized the region after the Last Glacial Maximum and Grassland would have a more ancestral origin than Savanna. Further, our results emphasize the importance of human-mediated dispersal in the reconfiguration of genetic diversity of species with potential pest capacity.

Plant carbohydrate content limits performance and lipid accumulation of an outbreaking herbivore.

Locusts are major intermittent threats to food security and the ecological factors determining where and when these occur remain poorly understood. For many herbivores, obtaining adequate protein from plants is a key challenge. We tested how the dietary protein : non-structural carbohydrate ratio (p : c) affects the developmental and physiological performance of 4th-5th instar nymphs of the South American locust, Schistocerca cancellata, which has recently resurged in Argentina, Bolivia and Paraguay. Field marching locusts preferred to feed on high carbohydrate foods. Field-collected juveniles transferred to the laboratory selected artificial diets or local plants with low p : c. On single artificial diets, survival rate increased as foods became more carbohydrate-biased. On single local plants, growth only occurred on the plant with the lowest p : c. Most local plants had p : c ratios substantially higher than optimal, demonstrating that field marching locusts must search for adequate carbohydrate or their survival and growth will be carbohydrate-limited. Total body lipids increased as dietary p : c decreased on both artificial and plant diets, and the low lipid contents of field-collected nymphs suggest that obtaining adequate carbohydrate may pose a strong limitation on migration for S. cancellata. Anthropogenic influences such as conversions of forests to pastures, may increase carbohydrate availability and promote outbreaks and migration of some locusts.

Spatial Variation in Body Size and Wing Dimorphism Correlates With Environmental Conditions in the Grasshopper Dichroplus vittatus (Orthoptera: Acrididae).

Wing dimorphism occurs widely in insects and involves discontinuous variation in a wide variety of traits involved in fight and reproduction. In the current study, we analyzed the spatial pattern of wing dimorphism and intraspecific morphometric variation in nine natural populations of the grasshopper Dichroplus vittatus (Bruner; Orthoptera: Acrididae) in Argentina. Considerable body size differences among populations, between sexes and wing morphs were detected. As a general trend, females were larger than males and macropterous individuals showed increased thorax length over brachypterous which can be explained by the morphological requirements for the development of flight muscles in the thoracic cavity favoring dispersal. Moreover, when comparing wing morphs, a higher phenotypic variability was detected in macropterous females. The frequency of macropterous individuals showed negative correlation with longitude and positive with precipitations, indicating that the macropterous morph is more frequent in the humid eastern part of the studied area. Our results provide valuable about spatial variation of fully winged morph and revealed geographic areas in which the species would experience greater dispersal capacity.

Cumulative effects of volcanic ash on the food preferences of two Orthopteran species.

Inert dusts are an early form of insecticide which is still in use. One of the most common inert dusts is volcanic ash. In order to study the reaction of rangeland grasshoppers, Dichroplus vittigerum (Acrididae) and a katydid, Burgilis mendosensis (Phaneropteridae), to the presence of volcanic ash in their food sources and how this reaction changed as a function of time, we conducted paired preference tests between clean leaves of their preferred host plant and leaves exposed to volcanic ash of different grain size. The behavioral response was measured as the rating on the Thurstonian preference scale of leaves with ash in relation to clean leaves. The results showed that the avoidance of volcanic ash increased as a function of time in both species. Both species studied are occasionally exposed to volcanic activity, and come from an area in which a volcanic eruption had recently occurred. As their populations did not decrease after the ash fall, we propose that some behavioral responses such as avoidance of places with ash, works as tolerance mechanism to inert dusts exposure.

[Biomass of Cornops aquaticum (Orthoptera: Acrididae) in wetlands of Northeast Argentina]. / Biomasa de Cornops aquaticum (Orthoptera: Acrididae) en humedales del nordeste de Argentina.

The estimation of biomass in insect populations is a key factor to quantify the available resources and energy fluxes in ecosystems food webs. Cornops aquaticum is a common herbivore in Eichhornia plants in wetlands of Northeast Argentina. We aimed to analyse its biomass variation, related to the different grasshopper age categories populations in two host-plants: Eichhornia azurea and Eichhornia crassipes. For this, standard samplings of C. aquaticum populations were carried out with an entomological net of 70 cm diameter in two wetlands with E. azurea and E. crassipes, in Corrientes and Chaco Provinces; besides, dry weight was also obtained (directly and indirectly), and a regression model to indirectly estimate the biomass from a linear dimension measure (hind femur length) is proposed. A total of 2307 individuals were collected and separated in different age categories; their abundance and linear dimension data were obtained. The model proposed was InDM=lna+b*lnH (where DM=dry mass, a and b are constants and H=hind femur length) (R2 = 0.97). The population biomass variations of C. aquaticum were due to the relative abundance of each age category and the grasshopper individual dry weight. No significant differences were found between populations biomasses obtained by direct and indirect methods in E. azurea and E. crassipes floating meadows. This model made easier the C. aquaticum biomass calculation for both individuals and the population, and accelerated the processing of high number of samples. Finally, high biomass values of populations and individual age category (especially in adults) emphasize the importance of C. aquaticum as a consumer and a resource for predators on Eichhornia floating meadows food webs.

Phenotypic Variation and Sexual Size Dimorphism in Dichroplus elongatus (Orthoptera: Acrididae).

Patterns of body size evolution are of particular interest because body size can affect virtually all the physiological and life history traits of an organism. Sexual size dimorphism (SSD), a difference in body size between males and females, is a widespread phenomenon in insects. Much of the variation in SSD is genetically based and likely due to differential selection acting on males and females. The importance of environmental variables and evolutionary processes affecting phenotypeic variation in both sexes may be useful to gain insights into insect ecology and evolution. Dichroplus elongatus Giglio-Tos is a South American grasshopper widely distributed throughout Argentina, Uruguay, most of Chile, and southern Brazil. In this study, we analyzed 122 adult females of D. elongatus collected in eight natural populations from central-east Argentina. Females show large body size variation among the analyzed populations and this variation exhibits a strong relationship with fecundity. Our results have shown that larger females were more fecund than smaller ones. We found that ovariole number varied along a latitudinal gradient, with higher ovariole numbers in populations from warmer locations. A considerable female-biased SSD was detected. SSD for three analyzed morphometric traits scaled isometrically. However, SSD for thorax length displayed a considerable variation across the studied area, indicating a larger relative increase in female size than in male size in warmer environmental conditions.

Biomasa de Cornops aquaticum (Orthoptera: Acrididae) en humedales del nordeste de Argentina / Biomass of Cornops aquaticum (Orthoptera: Acrididae) in wetlands of Northeast Argentina

The estimation of biomass in insect populations is a key factor to quantify the available resources and energy fluxes in ecosystems food webs. Cornops aquaticum is a common herbivore in Eichhornia plants in wetlands of Northeast Argentina. We aimed to analyse its biomass variation, related to the different grasshopper age categories populations in two host-plants: Eichhornia azurea and Eichhornia crassipes. For this, standard samplings of C. aquaticum populations were carried out with an entomological net of 70cm diameter in two wetlands with E. azurea and E. crassipes, in Corrientes and Chaco Provinces; besides, dry weight was also obtained (directly and indirectly), and a regression model to indirectly estimate the biomass from a linear dimension measure (hind femur length) is proposed. A total of 2 307 individuals were collected and separated in different age categories; their abundance and linear dimension data were obtained. The model proposed was lnDM=lna+b*lnH (where DM=dry mass, a and b are constants and H=hind femur length) (R²=0.97). The population biomass variations of C. aquaticum were due to the relative abundance of each age category and the grasshopper individual dry weight. No significant differences were found between populations biomasses obtained by direct and indirect methods in E. azurea and E. crassipes floating meadows. This model made easier the C. aquaticum biomass calculation for both individuals and the population, and accelerated the processing of high number of samples. Finally, high biomass values of populations and individual age category (especially in adults) emphasize the importance of C. aquaticum as a consumer and a resource for predators on Eichhornia floating meadows food webs. Rev. Biol. Trop. 63 (1): 127-138. Epub 2015 March 01.

La estimación de la biomasa en las poblaciones de insectos, es un factor clave para cuantificar los recursos disponibles y los flujos de energía en las redes tróficas de los ecosistemas. Cornops aquaticum es un herbívoro común en las plantas de Eichhornia en los humedales del nordeste de Argentina. Nuestro objetivo fue analizar la variación de su biomasa en relación a las distintas categorías de edades de la población de este acridio, en dos plantas huésped: Eichhornia azurea y Eichhornia crassipes. Para ello, se realizaron muestreos estándar de las poblaciones de C. aquaticum con una red entomológica de 70cm de diámetro, en dos humedales con E. azurea y E. crassipes en las provincias de Corrientes y Chaco; además, se obtuvo el peso seco de los individuos (de manera directa e indirecta) y, se propuso un modelo de regresión para estimar la biomasa de C. aquaticum de manera indirecta a partir de una medida de dimensión lineal (longitud del fémur posterior). Un total de 2 307 individuos fueron recolectados y separados en distintas categorías de edades; se obtuvo su abundancia y distintas medidas de dimensión lineal. El modelo propuesto fue lnPS=lna+b*lnH (donde PS=peso seco, a y b son constantes y H=longitud del fémur posterior) (R²=0.97). Las variaciones en la biomasa de las poblaciones de C. aquaticum se debieron a la abundancia relativa de cada categoría de edad y al peso seco individual de estos acridios. No hubo diferencias significativas entre la biomasa de las poblaciones de C. aquaticum obtenida por los métodos directo e indirecto en las praderas flotantes de E. azurea y E. crassipes. Este modelo facilita el cálculo de la biomasa individual y poblacional de C. aquaticum y acelera el procesamiento de un gran número de muestras. Finalmente, los valores altos de biomasa poblacional e individual de las categorías de edades (especialmente en adultos) enfatizan la importancia de C. aquaticum como consumidor y como recurso para los depredadores en las redes alimenticias de las praderas flotantes de Eichhornia.

Morphometric differentiation in Cornops aquaticum (Orthoptera: Acrididae): associations with sex, chromosome, and geographic conditions.

The water-hyacinth grasshopper Cornops aquaticum (Bruner) (Orthoptera: Acrididae) is native to South America and inhabits lowlands from southern Mexico to central Argentina and Uruguay. This grasshopper feeds and lays eggs on species from the genera Eichhornia and Pontederia. Particularly, Eichhornia crassipes is considered "the world's worst water weed," and the release of C. aquaticum was proposed as a form of biological control. Morphometric variation on the chromosomally differentiated populations from the middle and lower Paraná River and its possible association with geographic, sex, and chromosomal conditions was analyzed. Significant phenotype variation in C. aquaticum population was detected. C. aquaticum presents body-size sexual dimorphism, females being bigger than males. Female-biased sexual size dimorphism for all five analyzed traits was detected. The assessment of variation in sexual size dimorphism for tegmen length showed that this trait scaled allometrically, indicating that males and females did not vary in a similar fashion. The detected allometry was consistent with Rensch's rule demonstrating greater evolutionary divergence in male size than in female size and suggests that males are more sensitive to environmental condition. The analysis of morphometric variation in the context of chromosome constitution showed that the presence of fusion 1/6 was related to body-size variation. Fusion carriers displayed bigger body size than standard homozygotes. Besides, a positive relationship between tegmen length and the number of fused chromosomes was detected, showing a chromosome dose effect. Because the highest frequency of fusions has been found in the lower Paraná River, a marginal environment for this species, the results found would support the hypothesis that some supergenes located in the fusions may be favored in the southern populations, thus contributing to the establishment and maintenance of the polymorphism.

Studies in Mexican Grasshoppers: Liladownsia fraile, a new genus and species of Dactylotini (Acrididae: Melanoplinae) and an updated molecular phylogeny of Melanoplinae.

Liladownsia fraile gen. nov. sp. nov. Fontana, Mariño-Pérez, Woller & Song (Lila Downs' friar grasshopper) of the tribe Dactylotini (Orthoptera: Acrididae: Melanoplinae) is described from the pine-oak forest of the Sierra Madre del Sur Mountain Range in Oaxaca, Mexico. Taxonomic placement of this new genus is justified based on morphological characters as well as a molecular phylogeny. Information about the probable host plant, phenology, and known localities is also presented. We also present an updated molecular phylogeny of Melanoplinae, which includes representatives of five of the seven recognized tribes. The monophyly of the subfamily and the included tribes is tested and we find Dactylotini to be paraphyletic because of the placement of Hesperotettix Scudder, 1876. We also recover strong close relationships between the new genus and Perixerus Gerstaecker, 1873 and Dactylotum Charpentier, 1845.  

Age structure and feeding of the neotropical grasshopper Cornops aquaticum (Bruner) (Orthoptera: Acrididae) on water hyacinth.

We aimed to evaluate the variation in the age structure of Cornops aquaticum (Bruner) population and its relation to the host plant biomass and the feeding of the different age classes of this grasshopper on the water hyacinth Eichhornia crassipes along 2 years, in a Paraná River floodplain lake (Chaco, Argentina). Individuals of C. aquaticum were captured with a 70-cm diameter sweep and separated in nymphs A (instars I and II), nymphs B (instars III to VI), adult females, and adult males; host plant biomass was sampled using a ring with a 0.30-m(2) diameter. Relative daily feeding of C. aquaticum population was calculated by multiplying the number of individuals captured per minute by the daily consumption by individual obtained in each age classes. We found that the age structure and the relative daily feeding of C. aquaticum varied between seasons and years. The highest values of grasshopper abundance, leaf biomass, and relative daily feeding of C. aquaticum population were observed in summer 2006. Plant biomass was directly correlated with nymph abundance and not correlated with adult abundance. Plant biomass available as refuge (leaves), food (laminas), and oviposition site (petioles) to C. aquaticum represented up to 62% of the total plant biomass. The results obtained in C. aquaticum show the importance of considering total plant biomass and plant biomass available for herbivores separately. Our study highlights the need to find an adequate method to estimate the density of C. aquaticum and other semiaquatic grasshoppers in the Paraná River floodplain involving different seasons, years, and water phases (rising and falling).

Latitudinal clines in the grasshopper Dichroplus elongatus: coevolution of the A genome and B chromosomes?

Argentine populations of Dichroplus elongatus (Orthoptera: Acrididae) are polymorphic for B chromosomes. Previous studies showed that B chromosomes affect body size and some fitness components in Northwestern populations. We studied phenotype and B's variation patterns along a latitudinal cline as well as the relationship between karyotype and body size related traits in 17 populations from East. Body size related traits showed a 'saw tooth' pattern of variation being small at low and high latitudes and large at intermediate latitudes in most of the analysed populations. Analyses of variance and principal components demonstrated that in most analysed populations B carrier males are associated with a decrease in body size related traits with respect to individuals with standard karyotype. Accordingly with the relationship between karyotype and body size, an opposite pattern of latitudinal variation in the frequencies of B's with respect to body size variation was observed in this area. i.e. smaller individuals tend to have a higher frequency of B chromosomes. The comparison of the differentiation of both karyotype and body size traits with molecular neutral markers demonstrated the relative importance of selection moulding chromosome and phenotype variation. The observed pattern of phenotypic variation is likely to be the result of local adaptation to season length along the latitudinal gradient. The observed contrary pattern of B's clinal variation may reflect the population ability to maintain this chromosome in relation to the local adaptation. The available evidence indicates that the distribution of B chromosome frequency was shaped by selective factors.

Screening of Argentine native fungal strains for biocontrol of the grasshopper Tropidacris collaris: relationship between fungal pathogenicity and chitinolytic enzyme activity.

Tropidacris collaris (Orthoptera: Romaleidae) is a large and voracious grasshopper, which, in recent years, has become a recurrent pest in increasingly extensive areas of Argentina's northern provinces. In the present work chitinase activity was measured in 59 entomopathogenic fungal isolates native to Argentina, and the relationship between enzymatic activity and fungal virulence was assessed. Isolate LPSC 1067 caused the highest mortality on T. collaris nymphs (97.7 ± 1.22%). Nine isolates caused no mortality, while the remaining 49 caused mortalities ranging from 6.6 ± 0.3% (LPSC 770) to 91.06 ± 1.51% (LPSC 906). Several isolates revealed chitinolytic capabilities on test plates, although the activities differed with respect to the ratio of the chitin-decay-halo and fungal-colony diameters. A principal component analysis indicated that isolate LPSC 1067, obtained from a long-horned grasshopper (Orthoptera: Tettigoniidae), would be a potential candidate for T. collaris biocontrol because the strain exhibited the highest mortality, a shorter median lethal time, and a high enzymatic activity and growth rate.

Desarrollo post-embrionario, fecundidad y consumo de alimento de Dichroplus exilis (Orthoptera: Acrididae) bajo condiciones controladas

Postembryonic development, fecundity and food consumption of Dichroplus exilis (Orthoptera: Acrididae) under controlled conditions. Dichroplus exilis is a widely distributed species in Southern South America. Although there have been reports of D. exilis as an agricultural pest, some recent observations suggest that the damage attributed to D. elongatus may actually have been caused by D. exilis. This study was conducted to determine the postembryonic life cycle stages, fertility and food consumption of this species under controlled conditions (30°C, 14L-10D, 40% RH).Individuals employed belong to the laboratory-hatched first generation (F1), from adults (n=64, ♀=28, ♂=36) collected in natural grasslands near Rafaela, Santa Fe province in North- Eastern Argentina. Three cohorts of 16, 17 and 20 individuals were monitored independently in acetate tubes on a daily basis, until death of the last insect. Average fecundity was 381.84, 38.54 eggs per female. Egg-pod incubation time was 14.4, 1.08 days and six nymphal instars were recorded. Nymphal development time was 41.38, 0.71 days (I=8.73, 0.20; II=6.38, 0.24; III=5.64, 0.33; IV=7.15; 0.43; V=9.76, 0.54; IV=7.85, 0.95). The recorded food consumption was 9.89, 1.08 (mg/ind/day) for nymphs IV, 18.04, 0.73 (mg/ind/day) for nymphs V-IV, 16.76, 1.06 (mg/ind/day) for pre-reproductive males, 28.09, 1.81 (mg/ind/day) for pre-reproductive females, 7.71, 0.91 (mg/ind/day) for reproductive males and 13.06, 0.71 (mg/ind/day) for reproductive females, while the average adult food consumption, regardless of sex and reproductive status, was 16.41, 4.32mg/day. Average food consumption of adult females was 17.47, 1.15mg, and was significantly higher than that of males (10.83, 0.91mg). Data obtained in this study showed that D. exilis exhibits at least some of the biological attributes needed to configure an actual or potential agricultural pest, albeit not yet recognized as such. Field monitoring ...

La Subfamilia Melanoplinae tiene una relevancia central dentro de la acridiofauna Argentina. Varias especies suelen ser numéricamente dominantes en las comunidades de acridios del país y algunas constituyen serias plagas. El objetivo de este trabajo fue conocer el ciclo de vida postembrionario, la fecundidad y supervivencia de las hembras y el consumo de alimento de Dichruplus exilis bajo condiciones controladas (30°C; 40%HR y 14L-10O). Para ello se realizó el seguimiento de tres cohortes de 16, 17 y 20 individuos. El tiempo de incubación fue de 14.4±1.08 días. La duración del desarrollo ninfal fue 41.38; 0.71 días (I 8.73; 0.20, II 6.38; 0.24, III 5.64; 0.33, IV 7.15; 0.43, V 9.76; 0.54; IV 7.85; 0.95); la fecundidad promedio fue de 381.84, 38.54huevos/hembra. El consumo registrado fue de 9.89; 1.08 (mg/ind./día) para las ninfas de IV, 18.04; 0.73 (mg/ind./día) para las de V y IV, mientras que el consumo promedio de los adultos, sin diferenciar sexo y estado reproductivo, fue de 16.41; 4.32mg/día. Estos parámetros, al ser comparados con los de otras especies afines, indican que D. exilis exhibe atributos biológicos que condicen con los de otros melanoplinos considerados plaga.

The role of the host-specific grasshopper Cornops aquaticum (Orthoptera: Acrididae) as consumer of native Eichhornia crassipes (Pontederiaceae) floating meadows.

Cornops aquaticum is a widely distributed semiaquatic grasshopper in the Neotropics. The development, feeding and oviposition of C. aquaticum take place on Pontederiaceae, especially on species of Eichhornia. Several aspects of the feeding of C. aquaticum are studied because is one of the most important herbivores of the highly invasive floating Eichhornia crassipes in native areas. The aims of this paper were: (1) to quantify the amount of E. crassipes consumed by C. aquaticum, (2) to determine the growth rate and the conversion efficiency of food ingested by this grasshopper, and (3) to determine the possible effect of consumption on E. crassipes productivity. Thirty individuals from each specific age class were used in the experiment: nymphs A, nymphs B, adult males and adult females. Insects were individually confined in plastic pots with a leaf of E. crassipes. We estimated feeding by individual, consumption index (CI), relative growth rate (GR) and efficiency of conversion of ingested food to body substance (ECI). The impact of C. aquaticum consumption on E. crassipes floating meadows was assessed with the abundance of the grasshopper, and the available data on primary production of the host plant at the study site. Food intake of C. aquaticum was 11.23% of plant productivity. Food consumption, growth rate and food conversion efficiency of this grasshopper varied according to the specific age classes. Damage caused by C. aquaticum is high in comparison with the damage caused by other semiaquatic and grassland grasshoppers, however it is not enough to prevent the growth and coverage of native E. crassipes floating meadows because abundance of grasshoppers are realtively low and the growth rate and productivity of the host plant is high.

The role of the host-specific grasshopper Cornops aquaticum (Orthoptera: Acrididae) as consumer of native Eichhornia crassipes (Pontederiaceae) floating meadows

Cornops aquaticum is a widely distributed semiaquatic grasshopper in the Neotropics. The development, feeding and oviposition of C. aquaticum take place on Pontederiaceae, especially on species of Eichhornia. Several aspects of the feeding of C. aquaticum are studied because is one of the most important herbivores of the highly invasive floating Eichhornia crassipes in native areas. The aims of this paper were: (1) to quantify the amount of E. crassipes consumed by C. aquaticum, (2) to determine the growth rate and the conversion efficiency of food ingested by this grasshopper, and (3) to determine the possible effect of consumption on E. crassipes productivity. Thirty individuals from each specific age class were used in the experiment: nymphs A, nymphs B, adult males and adult females. Insects were individually confined in plastic pots with a leaf of E. crassipes. We estimated feeding by individual, consumption index (CI), relative growth rate (GR) and efficiency of conversion of ingested food to body substance (ECI). The impact of C. aquaticum consumption on E. crassipes floating meadows was assessed with the abundance of the grasshopper, and the available data on primary production of the host plant at the study site. Food intake of C. aquaticum was 11.23% of plant productivity. Food consumption, growth rate and food conversion efficiency of this grasshopper varied according to the specific age classes. Damage caused by C. aquaticum is high in comparison with the damage caused by other semiaquatic and grassland grasshoppers, however it is not enough to prevent the growth and coverage of native E. crassipes floating meadows because abundance of grasshoppers are realtively low and the growth rate and productivity of the host plant is high. Rev. Biol. Trop. 59 (3): 1407-1418. Epub 2011 September 01.

Cornops aquaticum es una tucura semiacuática Neotropical que vive asociada a las Pontederiaceae y constituye uno de los más importantes herbívoros de Eichhornia crassipes en áreas nativas. Los objetivos de este trabajo son: (1) cuantificar el consumo de C. aquaticum (2) determinar la tasa de crecimiento y la eficiencia de conversión del alimento ingerido de esta tucura, y (3) determinar el efecto del consumo en la productividad de E. crassipes. De cada categoría de edades de la población se utilizaron 30 individuos: ninfas A, ninfas B, adultos machos y hembras. Los insectos fueron confinados individualmente en recipientes con hojas de E. crassipes. Luego, se estimó el consumo por individuo, la tasa de consumo (CI), tasa de crecimiento (GR) y la eficiencia de conversión del alimento (ECI). La abundancia de C. aquaticum se determinó en verano y con los datos de productividad de la planta se calculó el efecto del consumo sobre E. crassipes. La tasa de consumo, tasa de crecimiento y la eficiencia de conversión del alimento varió entre las distintas categorías de edades de la población. C. aquaticum consume el 11% de la productividad primaria de E. crassipes. Si bien el consumo es alto, el daño no produce mermas importantes en los camalotales debido a la abundancia relativamente baja de C. aquaticum y la alta productividad de la planta huésped.

Feeding patterns of the aquatic grasshopper Cornops aquaticum (Bruner) (Orthoptera: Acrididae) in the middle Paraná river, Argentina.

The aquatic grasshopper Cornops aquaticum (Bruner) is native to South America and inhabits lowlands from southern Mexico to Central Argentina and Uruguay. This grasshopper is host-specific to aquatic plants of the genera Eichhornia and Pontederia. The objectives of this study were to analyze the feeding patterns of the aquatic grasshopper C. aquaticum in relationship to development stages and sex and to determine the food consumption rate in their host plant, Eichhornia crassipes. Samples were collected from April 2006 to May 2007 in different floodplain lakes of the Middle Parana River. The average consumption was greater in the females (0.127 g food/day ± 0.051) than in the males (0.060 g food/day ± 0.025). The feces of 361 nymphs and adults of this locust were examined and the most common tissue fragments found were of the water hyacinth (E. crassipes). In the initial nymphal stages (I, II and III), an exclusive consumption of E. crassipes was registered, while in the IV and V stages the choice included also other macrophytes. In summary, C. aquaticum presents polyphagy in the field, feeding on six macrophytes of different classes and families.

Feeding patterns of the aquatic grasshopper Cornops aquaticum (Bruner) (Orthoptera: Acrididae) in the middle Paraná river, Argentina

The aquatic grasshopper Cornops aquaticum (Bruner) is native to South America and inhabits lowlands from southern Mexico to Central Argentina and Uruguay. This grasshopper is host-specific to aquatic plants of the genera Eichhornia and Pontederia. The objectives of this study were to analyze the feeding patterns of the aquatic grasshopper C. aquaticum in relationship to development stages and sex and to determine the food consumption rate in their host plant, Eichhornia crassipes. Samples were collected from April 2006 to May 2007 in different floodplain lakes of the Middle Parana River. The average consumption was greater in the females (0.127 g food/day ± 0.051) than in the males (0.060 g food/day ± 0.025). The feces of 361 nymphs and adults of this locust were examined and the most common tissue fragments found were of the water hyacinth (E. crassipes). In the initial nymphal stages (I, II and III), an exclusive consumption of E. crassipes was registered, while in the IV and V stages the choice included also other macrophytes. In summary, C. aquaticum presents polyphagy in the field, feeding on six macrophytes of different classes and families.

[Postembryonic development, fecundity and food consumption of Dichroplus exilis (Orthoptera: Acrididae) under controlled conditions]. / Desarrollo post-embrionario, fecundidad y consumo de alimento de Dichroplus exilis (Orthoptera: Acrididae) bajo condiciones controladas.

Dichroplus exilis is a widely distributed species in Southern South America. Although there have been reports of D. exilis as an agricultural pest, some recent observations suggest that the damage attributed to D. elongatus may actually have been caused by D. exilis. This study was conducted to determine the postembryonic life cycle stages, fertility and food consumption of this species under controlled conditions (30 degrees C, 14L-10D, 40% RH). Individuals employed belong to the laboratory-hatched first generation (F1), from adults (n = 64, female = 28, male = 36) collected in natural grasslands near Rafaela, Santa Fe province in North-Eastern Argentina. Three cohorts of 16, 17 and 20 individuals were monitored independently in acetate tubes on a daily basis, until death of the last insect. Average fecundity was 381.84, 38.54 eggs per female. Egg-pod incubation time was 14.4, 1.08 days and six nymphal instars were recorded. Nymphal development time was 41.38, 0.71 days (I = 8.73, 0.20; II = 6.38, 0.24; III = 5.64, 0.33; IV = 7.15; 0.43; V=9.76, 0.54; IV = 7.85, 0.95). The recorded food consumption was 9.89, 1.08 (mg/ind/day) for nymphs IV, 18.04, 0.73 (mg/ind/day) for nymphs V-IV, 16.76, 1.06 (mg/ind/day) for pre-reproductive males, 28.09, 1.81 (mg/ind/day) for pre-reproductive females, 7.71,0.91 (mg/ind/day) for reproductive males and 13.06, 0.71 (mg/ind/day) for reproductive females, while the average adult food consumption, regardless of sex and reproductive status, was 16.41, 4.32 mg/day. Average food consumption of adult females was 17.47, 1.15 mg, and was significantly higher than that of males (10.83, 0.91mg). Data obtained in this study showed that D. exilis exhibits at least some of the biological attributes needed to configure an actual or potential agricultural pest, albeit not yet recognized as such. Field monitoring of grasshopper communities in areas where damage by D. exilis is suspected is envisaged in order to determine its possible status as a pest.

El comportamiento acústico de Fenestra bohlsii Giglio-Tos (Orthoptera: Acrididae: Gomphocerinae) / Acoustic behavior of Fenestra bohlsii Giglio-Tos (Orthoptera: Acrididae: Gomphocerinae)

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.