The Biology and some Population Parameters of the Grasshopper, Ronderosia bergi, Under Laboratory Conditions

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° 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 (R0) 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 (rm) was 0.21 ± 0.021 and the finite rate of population increase (λ) was 1.24 ± 0.026. The reproductive values (Vx) indicated that the largest contribution of females to the subsequent generation was between weeks 15 and 25

Diversidad y distribución de acridios (Orthoptera: Acridoidea) en pastizales del sur de la región pampeana, Argentina

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 distributio

Posternbryonie Development and Food Consumption of Dichroplus elongatus Giglio-Tos and Dichroplus maculipennis (Blanchard) (Orhtoptera: Acrididae: Melanoplinae) under Laboratory Conditions

Dichroplus maculipennis (Blanchard] and D. elongatus Giglio-Tos are two of the most important melanoplines in Argentina, both ecologically and economically. The postembryonic development and forage loss (consumption of Bromus brevis Ness + fallen material) caused by older nymphs (instars IV, V, VI) and adults of both species were studied under controlled conditions (30sC, 14L:10D, 40% RH). Five nymphal instars were recorded in D. elongatus, and six in D. maculipennis. Total nymphal development was similar in both species (£>. elongatus-. 32 ± 0.70 days; D. maculipennis-. 34.5 ± 0.37 days). Daily consumption increased from nymphal instars to pre-reproductive adult stage. In both species, pre-reproductive females had higher consumption rates than other stages considered (D. elongatus-. 30.6 ± 0.56 mg dry weight/day; D. maculipennis-. 48.7 ± 0.74 mg dry weight/ day). In the reproductive stage, consumption decreased significantly in both sexes. When feeding, D. maculipennis let some plant material to drop, increasing total loss. The percentage of fallen material was greater in reproductive adults, representing 3.9% and 2.9% of the total daily loss for males and females, respectively. Females and males of D. maculipennis were heavier than those of D. elongatus (P < 0.05), and daily consumption was significantly higher (P < 0.05). Regardless sex and reproductive status, adults of D. maculipennis consumed 29.1 ± 0.64 mg dry weight/day on average, while one of D. elongatus 20.0 ± 0.3 mg dry weight/ day.Centro de Estudios Parasitológicos y de VectoresFacultad de Ciencias Naturales y Muse

The biology and some population parameters of the grasshopper, Ronderosia bergi, under laboratory conditions

Some biological and population parameters of Ronderosia bergi (Stl) (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° 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 (R0) 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 (rm) was 0.21 ± 0.021 and the finite rate of population increase () was 1.24 ± 0.026. The reproductive values (Vx) indicated that the largest contribution of females to the subsequent generation was between weeks 15 and 25.Centro de Estudios Parasitológicos y de Vectore

Longevity and fecundity of Dichroplus maculipennis (Orthoptera, Acrididae) at non-outbreaking and outbreaking situations

Longevity and fecundity of Dichroplus maculipennis (Orthoptera, Acrididae) at non-outbreaking and outbreaking situations. Dichroplus maculipennis is one of the most characteristic and damaging grasshopper species of Argentina, mainly in areas of the Pampas and Patagonia regions. We estimated and compared the longevity and fecundity of adult female D. maculipennis under controlled conditions (30°C, 14L:10D, 40% RH) from individuals collected as last instar nymphs (VI) in the field and with a known recent history of low and high density conditions. Densities of D. maculipennis at the collecting sites were 0.95 individuals per m2 in 2006 and 46 ind/m2 in 2009, representing non-outbreaking and outbreaking situations, respectively. Adult female longevity in 2006 (67.96 ± 3.2 days) was significantly higher (p 0.05). The fecundity curves showed that the highest values were at weeks 11 and 13 for the 2006 females, and at week 6 for those of 2009. Since the daily oviposition rate at low and high densities was not significantly different, the diminished fecundity rate at high density is attributable to their reduced longevityLongevidade e fecundidade de Dichroplus maculipennis (Orthoptera: Acrididae: Melanoplinae) em situações de “nonoutbreaking” e “outbreaking”. O gafanhoto Dichroplus maculipennis é um dos mais característicos e prejudiciales da Argentina, principalmente nas regiões das Pampas e da Patagonia. O objetivo deste estudo foi estimar e comparar a longevidade e fecundidade das fêmeas adultas do D. maculipennis sob condições controladas (30°C, 14 luz: 10 obscuridad, 40% RH) a partir do indivíduos coletados em campo como ultimo estadio ninfal (VI) e con historia recente conocida de baixas e altas densidades. As densidades de D. maculipennis nos locais de coleta foram de 0.95 indivíduos por m2 em 2006 e 46 indivíduos/m2 em 2009, representando situações de “non-outbreaking” e “outbreaking”, respectivamente. A longevidade das fêmeas adultas em 2006 (67.96 ± 3.2 dias) foi significamente maior (p < 0.05) do que as de 2009 (37.44 ± 1.98 dias). O número de oviposiçãos por fêmea foi de 3.32 ± 0.44 para 2006 e 1.62 ± 0.26 para 2009. A fecundidade média em 2006 (89.29 ± 11.9 ovos/fêmea) foi significativamente maior (p < 0.05) do que a das fêmeas de 2009 (36.27 ± 5.82 ovos/fêmea). As curvas de fecundidade mostraram que os valores mais elevados ocorreram nas 11ª e 13ª semanas de 2006, e na 6ª semana para à quelas de 2009. Comparando a taxa diária de oviposição para altas e baixas densidades, não apresentaram diferenças significativas (p > 0.05). No entanto, as baixas taxas de fecundidade das fêmeas em densidades elevadas, se devem, provavelmente à longevidade reduzida.Centro de Estudios Parasitológicos y de VectoresFacultad de Ciencias Naturales y Muse

Naturalized, newly-associated microsporidium continues causing epizootics and expanding its host range

Examination of grasshoppers sampled at two sites, one in western Pampas and one in northwestern Patagonia, both in Argentina, revealed the occurrence of two new epizootic events of the allochthonous microsporidium Paranosema locustae which became naturalized in grasshopper communities of those areas after introductions from its native land in North America in the late seventies-early eighties and mid-nineties, respectively. In the Pampas site, P. locustae was found infecting six out of eight grasshopper species collected at an overall prevalence of 38.8 % and a maximum of 50 %. In the Patagonia site, P. locustae was detected in four out of six species at an overall prevalence of 10.5 % and a maximum of 34.3 %. Two of the species affected, one in the Pampas, the gomphocerine Amblytropidia australis, and one in Patagonia, the melanopline Dichroplus vittigerum, constitute new host records for P. locustae, expanding its field host range in Argentina to 24 species of grasshoppers. In addition, bioassays were performed on three other grasshopper species selected based on several criteria. The tristirid Bufonacris claraziana and the gomphocerine Borellia bruneri turned out to be not susceptible to P. locustae while the melanopline Scotussa cliens was highly susceptible. All in all, results highlight not only the uniqueness of P. locustae among the Microsporidia that allowed for its development as a biocontrol agent but also the suitability of grasshopper communities in the Pampas and Patagonia to fully express such uniqueness, possibly even more so as an allochthonous parasite against autochthonous novel hosts.Fil: Lange, Carlos Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Mariottini, Yanina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Plischuk, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Cigliano, Maria Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; Argentin

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°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 of grasshopper communities in areas where damage by D. exilis is suspected is envisaged in order to determine its possible status as a pest

Postembrionic development and reproductive parameters of the grasshopper pest Borellia bruneri (Acrididae: Gomphocerinae) under controlled conditions

Borellia bruneri, a common grasshopper in much of the grasslands of Argentina and Uruguay, is considered, according to the categories widely accepted for defining the pest status of grasshopper species, a “Frequent plague of importance”. In order to determine fundamental aspects of its biology and reproduction, three cohorts of B. bruneri were monitored under controlled conditions (30º C, 14L: 10D, 40% RH). The total duration of nymphal development was 50.6 days, both males and females having five nymphal instars. There was a significant difference in the duration of the different stages within each cohort. In the three cohorts, the first instar duration (12.87 days) was longer than the rest, approximately 5.6 days more than the second that was the shortest (7.26 days). The average longevity of female adults was 56.6 days, and in males, 54.4 days. The number of egg-pods per female was 3.5 and the amount of eggs per egg-pod was 10.8. Mean fecundity was 37.9 eggs per female with an oviposition rate of 1.20 eggs/female/day. Finally, knowing the life cycle of B. bruneri is relevant in order to optimize the control measures for this species.Fil: Mariottini, Yanina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: de Wysiecki, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Alberti, A.. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; ArgentinaFil: Lange, Carlos Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentin

Pérdida de forraje ocasionada por diferentes densidades de Dichroplus maculipennis (Acrididae: Melanoplinae) en una pastura de Festuca arundinacea Schreb

Dichroplus maculipennis es una de las especies de tucura más característica y perjudicial de Argentina, principalmente en zonas de la región pampeana y la Patagonia. En años de explosiones poblacionales esta especie ocasiona importantes daños en pastizales naturales, pasturas implantadas y en diversos cultivos. Considerando esto, el objetivo principal de este estudio fue estimar la pérdida de forraje ocasionada por diferentes densidades de D. maculipennis en el estado adulto, sobre una pastura de valor forrajero como Festuca arundinacea, en condiciones de campo. La experiencia se realizó en un campo del partido de Tandil, durante el mes de enero de 2016. Se utilizaron jaulas donde se colocaron individuos adultos de D. maculipennis en una proporción 1:1 de machos y hembras. Se estimó la pérdida de forraje ocasionada por tres densidades diferentes: 8 ind/m2, 16 ind/m2 y 32 ind/m2. Se realizaron tres réplicas por densidad ensayada y también se establecieron tres jaulas sin tucuras como control. La biomasa cosechada al final de la experiencia en las jaulas control fue 337,8 ± 7,5 g/m2, en las jaulas con una densidad de 8 ind/m2 fue de 262,9 ± 11,8 g/m2, en aquellas con 16 ind/m2 fue de 227,6 ± 6 g/m2 y en las jaulas con 32 ind/m2 fue de 154,6 ± 9,9 g/m2. Las tres densidades utilizadas ocasionaron una disminución significativa en la biomasa de F. arundinacea respecto del control (p<0,0001). Asimismo, la biomasa vegetal cosechada en las jaulas con la mayor densidad de tucuras fue significativamente menor a la obtenida en las jaulas con las otras dos densidades (p <0,05). En promedio un individuo por día ocasionó una pérdida de forraje de 0,236 ± 0,02 g. A partir de los resultados obtenidos, se puede inferir que 8 ind/m2 producirían una pérdida de forraje de 749 kg/ha. Con 16 ind/m2 la pérdida sería de 1107,4 kg/ha y con 32 ind/m2 la pérdida sería de 1873 kg/ha. Esta última densidad ocasionaría una disminución del 55% de la biomasa de la pastura en el lapso de un mes.The grasshopper Dichroplus maculipennis is considered one of the most characteristic and damaging species of Argentina, mainly in areas of Pampas and Patagonia regions. In outbreak years, this species causes serious damage to grasslands as well as to implanted pastures and various crops. Considering this, the main goal of this study was to estimate the loss of forage caused by different densities of D. maculipennis in adulthood on a pasture of forage value as Festuca arundinacea, under field conditions. The experience was conducted in a field of Tandil County, during January 2016. Adult individuals of D. maculipennis were placed in cages in a sex ratio 1:1. Forage loss caused by three different densities was estimated with 8 ind/m2, 16 ind/m2 and 32 ind/m2. Three replicates were performed for each assayed density; also three cages were established without grasshoppers as control. The harvested biomass at the end of the experiment in control cages was 337,8 ± 7,5 g/m2, in cages with a density of 8 ind/m2 was 262,9 ± 11,8 g/m2, those with 16 ind / m2 was 227,6 ± 6 g / m2 and in cages with 32 ind/m2 was 154,6 ± 9,9 g/m2. The three densities caused a significant decrease in the biomass of F. arundinacea respect to the control (p <0,0001). Plant biomass harvested from cages with the highest density of grasshoppers was significantly lower than that obtained from cages with the other two densities (p <0,05). One insect per day caused a forage loss of 0,02 ± 0,236 g/m2, on average. From the results, it can be inferred that a density of 8 ind/m2 would produce a forage loss of 749 kg/ha, 16 ind/m2 would produce a forage loss of 1107,4 kg/ha, and with 32 ind/m2 the loss would be 1873 kg/ha. The latter would cause a decrease of 55% of the biomass of pasture in one month.Gerencia de Comunicación e Imagen Institucional, DNA SICC, INTAFil: Mariottini, Yanina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Estudios Parasitológicos y de Vectores; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; ArgentinaFil: De Wysiecki, M.L. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Estudios Parasitológicos y de Vectores; Argentina. Universidad Nacional de La Plata, Facultad de Ciencias Naturales y Museo; ArgentinaFil: Lange, C.E. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Estudios Parasitológicos y de Vectores; Argentina. Buenos Aires (provincia). Comisión de Investigaciones Científicas; Argentin

Spatio-temporal occurrence of infections by the microsporidium liebermannia dichroplusae

Liebermannia dichroplusae is an intracellular parasite that develops in the epithelium cells of the Malpighian tubules of the univoltine melanopline Dichroplus elongatus, a common and widespread grasshopper in southern South America that readily becomes an agricultural pest when outbreaks occur. Heavy infections by L. dichroplusae cause conspicuous pathologies and are clearly deleterious to the host. Transovarial transmission is the main route of infection in L. dichroplusae while horizontal transmission appears to be rare. The examination of 243 samples containing a total of almost 17.000 nymphs and adults of D. elongatus collected at 88 localities in eight provinces of Argentina between 1984 and 2017 showed that L. dichroplusae appears to occur only in the central-eastern Pampas region (Buenos Aires province) while its host inhabits almost the whole country. It is hypothesized that the relatively localized occurrence of L. dichroplusae compared to the wide geographical range of its host, could be the result of the combination of the dominant mode of transmission of the pathogen the pathologies it causes, and the main type of dispersal of D. elongatus.Fil: Lange, Carlos Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Mariottini, Yanina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: de Wysiecki, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Cigliano, Maria Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; Argentin