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The aim of this study was to analyze the food utilization efficiencies and the relative growth and consumption rates of different developmental stages and sexes of D. maculipennis under controlled conditions on wheat, oat, corn, and soybean plants, important crops in the Pampas region of Argentina. As expected from a polyphagous species, D. maculipennis was observed to consume all four of the plant species offered. Nevertheless, the consumption of both nymphs and adults was differentiated. Oat and wheat were more consumed than corn and soybean. Females presented higher consumption rates (384.6 ± 30.64 mg/individual/day) than males (278.71 ± 24.26 mg/individual/day). Adult females had the highest growth rate, followed by nymphs of the same sex, and then adult males. The highest values of ECI and ECD were obtained in soybean; females had higher values of food efficiencies than males, and nymphs had greater values than adults. In relation to this, soybean was the highest quality food; the amount of nitrogen present in soybean was approximately twice that found in the other species. The nutritional needs of D. maculipennis might have been satisfied by feeding on low quantities of soybean, which is, among the food offered, the most "nutritionally balanced food". [ABSTRACT FROM AUTHOR]

This study examined the effects of strainBeauveria bassiana(LPSC 1067) on nymphal development time, fecundity and adult survival inDichroplus maculipennisandRonderosia bergiunder laboratory conditions. It was observed that infection with 1×103conidia/ml altered nymphal development time, fecundity and adult survival in both species. Mortality ofD. maculipennisduring third through the last instar (sixth) was significantly higher among treated nymphs (66±3.8%) than in controls (15±1.7%). Similarly, mortality inR. bergiduring third through the last instar (fifth) was higher in treated nymphs (71±2.8%) than in controls (19±1.5%). Nymphal development times of both infectedD. maculipennisandR. bergiwere longer than controls. On the other hand, among survivors of both the species, control adults lived longer than infected adults. Finally, control grasshoppers of both species were much more successful reproductively than infected grasshoppers. [ABSTRACT FROM PUBLISHER]

Fungi are the most important entomopathogens in the natural regulation of insect populations. They have a wide distribution and significant advantages as biological control agents. Prospecting for new native strains of entomopathogenic fungi in the Pampas region has not yet been carried out. The main objectives of this study were isolating and identifying strains of different species of entomopathogenic fungi that naturally infect grasshopper species in the Pampas region and determining, through laboratory tests, their virulence and pathogenicity on nymphs of the pest grasshopper Dichroplus maculipennis. Furthermore, whether the phylogenetic relationships between Beauveria bassiana isolates would be associated with virulence and pathogenicity or geographical distribution. Thirty-four isolates of entomopathogenic fungi were obtained from different grasshopper species corresponding to eleven sites in three counties in the center of Buenos Aires province. There were 31 isolates of B. bassiana and 3 of Metarhizium genus. These isolates scored 66.6% (LPSc 1443) and 100% (LPSc 1441, LPSc 1445, and LPSc 1476) of mortality against third-instar nymphs of D. maculipennis, and these last cause death at 4.86 ± 0.20, 4.80 ± 0.17 and 5 ± 0.15 MST days, respectively. An association between phylogenetic relationships and geographical distances in B. bassiana was found.

The goal of this study was to assess the status of Dichroplus elongatus and Borellia bruneri as actual agricultural pests in the Argentine Pampas by determining their abundance, distribution, and associated forage loss. The study was conducted in Laprida and Tandil, two counties in Buenos Aires province. In each county 20 sampling sites were established and monitored from 2012 to 2018. B. bruneri was more abundant and with a wider distribution in Laprida (91.4% of the sites) than in Tandil (42.1% of the sites) while D. elongatus abundance was significantly higher from 2012 to 2016 in Tandil than in Laprida and its distribution was wide in Laprida (75% of the sites) and very wide in Tandil (77.14%). Under field-cage conditions forage loss caused at three different densities (8, 16, and 32 ind/m2) of D. elongatus and B. bruneri adults on a pasture of Festuca arundinacea was estimated. Forage loss caused by D. elongatus was significantly higher than that caused by B. bruneri. Dichroplus elongatus caused a significant decrease in biomass at the three densities respect to the control, while B. bruneri only caused a significant decrease at the highest density. Our study suggests that although the gomphocerine B. bruneri is an abundant and widely-distributed species capable of doing some damage in the grasslands of the southern Pampas, it is comparatively much less harmful than the melanopline D. elongatus.

In this study, the effects of strain Beauveria bassiana (LPSC 1067) as an endophyte in corn plants on consumption, fecundity, and food preference of Dichroplus maculipennis were examined. We observed that the daily consumption by grasshoppers fed with control plants was almost twice that of those that were fed treated plants. Significant differences in fecundity of grasshoppers that were fed with treated plants compared with those that only fed on control plants were also observed. The number of eggs laid per female fed with control plants was 27.2, while the number of eggs laid per female that were fed during 15 d with treated plants was 17.7. Similar results were observed when the number of embryonated eggs was evaluated. The highest number of embryonated eggs were recorded in those females that only fed on control plants (96%) while fewer embryonated eggs were recorded in grasshoppers fed for 15 d with treated plants only (25%). In relation to food preference the average consumption rate for D. maculipennis females on control corn plants was 303.8 ± 24.5 mg while it was only 25 ± 2.1 mg on plants treated with B. bassiana as an endophyte. In summary, we observed that B. bassiana as a corn plant endophyte negatively affected the daily consumption rate, fecundity and food preference of D. maculipennis., (© The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America.)

South American melanopline grasshoppers display a disproportionate number of derived karyotypes, including many cases of neo-sex chromosome systems. This is especially true of the genus Dichroplus and its Maculipennis species group. We analyzed the karyotype and neo-sex chromosomes in mitosis and meiosis of Dichroplus maculipennis and D. vittigerum from Argentina using conventional and fluorescent cytogenetic protocols in order to elucidate the behavior and origin of these neo-XY systems in relation to the current phylogeny of this group. Our results showed that D. maculipennis (2n = 22♂/22♀; neoXY/neoXX) and D. vittigerum, whose karyotype is described here for the first time (2n = 18♂/18♀; neoXY/neoXX), show highly evolved neo-XY systems, although with significant differences between them. Furthermore, both species differ for two autosomal fixed Robertsonian fusions present in D. vittigerum. Analysis of karyotypic character state optimization strongly suggests the independent origin and evolution of neo-sex systems within this species group.

In Argentina, the grasslands of Pampas region comprise approximately 15% of the country. As in other grasslands of the world, grasshoppers are among the most important native herbivores. Their economic importance has been recognized in Argentina since the mid to late nineteenth century, since outbreaks of different species have become recurrent phenomena. Therefore, the main objective of this work was to study their diversity and distribution in grasslands of the Southern Pampas region (Laprida county, Buenos Aires province), as one of the most affected areas. The study was conducted during five seasons (2005-10). Sampling sites were represented by the most common plant communities in this area, classified in four categories: native grasslands, disturbed grasslands, implanted pastures and halophilous grasslands. The samplings were conducted from mid-spring to early autumn, with five or six samples per season. We estimated the following population descriptors: species richness (S), eveness (E), dominance (J), and diversity index (H'). In order to evaluate the similitude of the grasshopper communities present in the different plant communities, we used qualitative and quantitative coefficients of similitude. A total of 22 species of grasshoppers were collected, of which 21 belong to the family Acrididae. The subfamily Melanoplinae was the most diverse with eight species. The largest species richness was recorded in native grasslands (18). The different communities of grasshoppers had similar indices of evenness and dominance (p>0.05). Considering all plant communities, the average value of Shannon-Wiener index was 1.58+/-0.075. There was a positive correlation between evenness index and species richness (p<0.05). The diversity index H' was different between plants communities (p<0.05), and it was higher in the disturbed grassland (1.75+/-0.096, p<0.05) than in the halophilous grasslands (1.34+/-0.12). Native and disturbed grasslands had a higher plant richness than halophilous grasslands and implanted pastures (p<0.05). There was a positive relationship between plant richness and grasshoppers species richness, and diversity of grasshoppers. According to the qualitative indices applied, the similitude between different grasshopper communities was higher than 60%. In general, the species that had a higher frequency of occurrence showed greater abundance and distribution. Covasacris pallidinota, Dichroplus elongatus, D. maculipennis, Borellia bruneri and B. pallida were the most widely distributed species, most of them (12) showed a restricted distribution and few (five) an intermediate distribution.

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.

Some biological and population parameters of Ronderosia bergi (Stål) (Orthoptera: Acrididae: Melanoplinae) were estimated by monitoring five cohorts of the first generation (F1) of individuals born in captivity from grasshoppers collected in the South of Misiones province, northeastern Argentina, and held under controlled conditions (30 degrees C, 14:10 L:D, 40% RH). The mean embryonic development time was 40.6 +/- 1.7 days. Five nymphal instars were recorded. Total duration of nymphal development was 30.8 +/- 0.54 days. The mean lifespan of cohorts was 22.6 +/- 0.7 weeks. The number of egg-pods per female was 7.6 +/- 1.44, and the amount of eggs per egg-pod was 16.45 +/- 0.85. Mean fecundity was 125 +/- 5.83 eggs per female with an oviposition rate of 1.55 +/- 0.57 eggs/female/day. Survivorship curves showed that mortality was concentrated in the final weeks of adulthood, and the life expectancy curve decreased accordingly. The population parameters estimated gave the following values: the net rate of reproduction (R(0)) was 46.75 +/- 11.2, generation time (T) was 18.87 +/- 1.67 weeks, duplication time (D) was 3.31 +/- 0.34, the intrinsic rate of population growth (r(m)) was 0.21 +/- 0.021 and the finite rate of population increase (lambda) was 1.24 +/- 0.026. The reproductive values (V(x)) indicated that the largest contribution of females to the subsequent generation was between weeks 15 and 25.

During a survey for grasshopper pathogens in Argentina in 2005-2006, individual Covasacris pallidinota from halophylous grasslands in Laprida, Buenos Aires province were found to be infected with a microsporidium. Infection was restricted to the salivary gland epithelial cells. The microsporidium produced ovocylindrical spores averaging 2.6+/-0.28 x 1.4+/-0.12 microm (range 2.2-3.4 x 1.1-1.7 microm), which resembled in size and shape the spores of Liebermannia patagonica and L. dichroplusae, two recently described species that also parasitize Argentine grasshoppers. The life cycle of the microsporidium included the formation of polynucleate, diplokaryotic, moniliform, merogonial plasmodia wrapped in flattened cisterns of the host endoplasmic reticulum (ER). Plasmodia divided to produce diplokaryotic cells. The latter underwent elongation, dissociation of diplokarya counterparts, vacuolization, dismantling of the host ER envelope, and deposition of electron-dense material outside the plasma membrane. The resultant binucleate sporogonial plasmodia divided into two uninucleate sporoblasts, which eventually transformed into spores. Uninucleate spores contained a lamellar polaroplast, embraced by an elongated polar sac, anchoring disc, 3-5 polar filament coils, and a cluster of anastomizing tubules (sporoblast trans-Golgi, posterosome) at the posterior end. Sequence similarity of the SSU rDNA of the newly discovered microsporidium (Genbank accession no. EU709818) to L. patagonica and L. dichroplusae was 99% and 97%, respectively, suggesting that the three species belong to one genus. All three species fell into one clade in SSU rDNA-based phylogenetic trees produced by neighbor joining, maximum parsimony, and maximum likelihood analyses with 100% statistical support. We assign the name Liebermannia covasacrae to this microsporidium. It can be easily differentiated from both congeners by host species, tissue tropism, type of sporogony, and several features of morphology. Comparison of the three Liebermannia spp. demonstrates that the nuclear phase (dikaryotic versus monokaryotic spores) and type of sporogony (polysporous versus disporous) may vary in closely related species.