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Resumen En la ciudad de La Plata se encuentra el género Tityus con registros desde 1943. Se estudió la distribución territorial del género Tityus en esta ciudad y su expansión en los últimos 15 años a partir de las consultas recibidas en el Laboratorio de Aracnología del CEPAVE, provenientes de particulares e instituciones públicas y privadas. Se recibieron 189 consultas desde el año 2005 al 2020. Se utilizó el programa QGIS para geolocalizar cada escorpión con capas de trazado urbano y desagües pluviales. Para el análisis espacial de distribución se consideró un home range de una hectárea por individuo para el cálculo de área y en los casos de áreas de influencias solapadas durante el mismo año se consideró el área como la unión de las mismas. El género Tityus en la ciudad de La Plata está representado por las especies T. carrilloi y T. confluens ambas de interés sanitario y de hábitos sinantrópicos, que ocupan dos zonas diferentes bien definidas. El análisis de la dispersión independiente en las dos zonas indicaría que podrían usar los desagües para dispersarse, y al ser inconexos estos no habría flujo de escorpiones entre ambas zonas. La colonización de estas especies en la zona en estudio se vio afianzada para T. confluens a partir del año 2005 y para T. carrilloi a partir del 2011. Los mayores registros son en los meses cálidos, desde enero a abril, siendo este último el de mayor valor. Septiembre es el único mes sin denuncia. La tasa de expansión calculada fue de 4.42 ha/año.

Abstract In the city of La Plata occurs the genus Tityus with records dating back to 1943. The territorial distribution of the genus Tityus in this city and its expansion was studied based on inquiries received at the CEPAVE Arachnology Laboratory from individuals and public and private institutions. 189 inquiries were received from 2005 to 2020. The QGIS program was used to geolocate each scorpion with urban layout layers and storm drains. For the spatial analysis of distribution, a home range of one hectare per individual was considered to calculate the area and in the cases of areas of overlapping influences during the same year, the area was considered as their union. The genus Tityus in the city of La Plata is represented by the species T. carrilloi and T. confluens, both of health interest and of synanthropic habits, which occupy two different well-defined areas. The analysis of the independent dispersion in the two zones would indicate that they could use the drains to disperse, and since they are unconnected there would be no flow of scorpions between both zones. The colonization of these species in the study area was strengthened for T. confluens as of 2005 and for T. carrilloi as of 2011. The highest records are in the warm months, from January to April, the latter being of higher value. September is the only month without complaints. The expansion rate calculated was 4.42 ha/year.

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Resumen En el presente estudio se dan a conocer por primera vez, datos sobre la interacción entre ejemplares de avispas de la especie Epipompilus platensis Roig Alsina, 2017 (Hymenoptera, Pompilidae) y arañas de la especie Ariadna mollis (Holmberg 1876) (Araneae, Segestriidae), en las localidades de Punta Lara (partido de Ensenada) y José Hernández (partido de La Plata), ambas pertenecientes a la provincia de Buenos Aires. Se recolectaron varios ejemplares de A. mollis en el mes de abril del 2015, y se seleccionaron aquellos que presentaban un huevo o una pequeña larva adherida al dorso del abdomen. Se mantuvieron bajo observación en bioterio hasta completar el desarrollo al estado adulto de la avispa. Del total de las arañas colectadas, el 9.6% se encontró parasitado por avispas. De ese porcentaje, cuatro larvas de E. platensis llegaron al estado adulto (tres hembras y un macho). Los resultados obtenidos contribuyen al conocimiento de una nueva interacción entre avispas y arañas.

Abstract In the present study, data on the interaction between wasp specimens of the species Epipompilus platensis Roig Alsina, 2017 (Hymenoptera, Pompilidae) and spiders of the species Ariadna mollis (Holmberg 1876) (Araneae, Segestriidae) are presented for the first time. Present in the localities of Punta Lara (Partido de Ensenada) and José Hernández (Partido de La Plata), both belonging to the province of Buenos Aires. Several specimens of A. mollis were collected on april 2015, and those that presented an egg or a small larva attached to the back of the abdomen were selected. They were kept under observation in a bioterium until completing the development of the wasp's adult state. Of the total spiders collected, 9.6% were parasitized by wasps. Of that percentage, four larvae of E. platensis reached the adult stage (three females and one male). The results obtained contribute to the knowledge of a new interaction between wasps and spiders.

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Resumen Los arácnidos son un grupo megadiverso, en el cuál están las arañas y los escorpiones. Si bien todas las especies de ambos grupos tienen veneno, solo algunas son peligrosas para el ser humano, pudiendo causar hasta la muerte, y ocupan un lugar importante en las tradiciones de muchos pueblos. El objetivo del presente trabajo es conocer, mediante una encuesta, cuáles son los conocimientos de las personas sobre arañas y escorpiones y poner a prueba mitos y verdades mediante preguntas y repreguntas. Los resultados muestran un desconocimiento considerable en la población participante, especialmente con avanzado nivel educativo, que aceptan mitos por encima de los descubrimientos científicos verdaderos; además la respuesta entre varones y mujeres difiere de manera significativa en muchas preguntas. Estos resultados obligan a pensar políticas de educación que reviertan esos conocimientos erróneos basados en prejuicios o información de dudosa veracidad, por aquellos basados en la evidencia científica. Esto permitiría un manejo racional de estos grupos y así brindar medidas de prevención eficientes y pautas de acción si ocurriese un accidente.

Resumo Os aracnídeos são um grupo megadiverso, que inclui aranhas e escorpiões. Embora todas as espécies de ambos os grupos tenham veneno, só algumas são perigosas para o ser humano, podendo causar até a morte, e ocupam lugar importante nas tradições de muitas cidades. O objetivo do presente trabalho é conhecer, através de uma pesquisa, quais são os conhecimentos das pessoas sobre aranhas e escorpiões, e testar mitos e verdades por meio de perguntas e perguntas cruzadas. Os resultados mostram considerável desconhecimento por parte da população participante, em especial aquela com nível avançado de educação, que acredita em mitos mais frequentemente do que nas verdadeiras descobertas científicas; além disso, a resposta entre homens e mulheres difere significativamente em muitas questões. Esses resultados nos levam a pensar em políticas educacionais que revertam esses conhecimentos errôneos baseados em preconceitos ou informações de veracidade duvidosa, para aqueles baseados em evidências científicas. Isso permitiria um manejo racional dessas espécies, possibilitando medidas de prevenção eficientes e diretrizes para ação caso ocorra um acidente.

Abstract Arachnids are a megadiverse group, that include spiders and scorpions. Although the species of both groups are poisonous, only a few are dangerous to human beings, having the potential of causing death, and have an important place in the traditions of many cultures. This work aimed to evaluate, by means of a survey, the knowledge of the public about spiders and scorpions, and to test myths and truths through questions and cross-examinations. Results show a significant lack of awareness among the participants, especially those with higher level of education, who accept myths over true scientific discoveries; besides answers to many questions differ significantly between men and women. These results require the development of education policies that replace such erroneous knowledge based on prejudices or information of doubtful veracity, for scientific facts. This would allow a rational management of these species and thus provide efficient preventive measures and guidelines in case of accidents.

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The aim of this study was to identify entomopathogenic fungi infecting spiders (Araneae) in a protected area of Buenos Aires province, Argentina. The Araneae species identified was Stenoterommata platensis. The pathogens identified were Lecanicillium aphanocladii Zare & W. Gams, Purpureocillium lilacinum (Thom) Luangsa-ard, Houbraken, Hywel Jones & Samson and Ophiocordyceps caloceroides (Berk & M.A. Curtis). This study constitutes the southernmost records in the world and contributes to expanding the knowledge of the biodiversity of pathogenic fungi of spiders in Argentina.

El objetivo de este estudio fue identificar hongos entomopatógenos de arañas en un área protegida de la provincia de Buenos Aires, Argentina. La especie de araña identificada fue Stenoterommata platensis. Los patógenos identificados fueron Lecanicillium aphanocladii Zare y W. Gams, Purpureocillium lilacinum (Thom) Luangsa-ard, Houbraken, Hywel Jones y Samson y Ophiocordyceps caloceroides (Berk y M.A. Curtis). Este estudio constituye el registro más austral del mundo y contribuye a ampliar el conocimiento de la biodiversidad de hongos patógenos de arañas en Argentina.

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"Black widow" spiders belong to the genus Latrodectus and are one of the few spiders in the world whose bite can cause severe envenomation in humans and domestic animals. In Argentina, these spiders are distributed throughout the country and are responsible for the highest number of bites by spiders of toxicological sanitary interest. Here, we studied the toxicity and some biochemical and immunochemical characteristics of eighteen venom samples from Latrodectus spiders from eight different provinces of Argentina, and the neutralization of some of these samples by two therapeutic antivenoms used in the country for the treatment of envenomation and by a anti-Latrodectus antivenom prepared against the venom of Latrodectus mactans from Mexico. We observed important toxicity in all the samples studied and a variation in the toxicity of samples, even in those from the same region and province and even in the same Latrodectus species from the same region. The therapeutic antivenoms efficiently neutralized all the venoms studied.

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The aim of this study was to identify entomopathogenic fungi infecting spiders (Araneae) in a protected area of Buenos Aires province, Argentina. The Araneae species identified was Stenoterommata platensis. The pathogens identified were Lecanicillium aphanocladii Zare & W. Gams, Purpureocillium lilacinum (Thom) Luangsa-ard, Houbraken, Hywel Jones & Samson and Ophiocordyceps caloceroides (Berk & M.A. Curtis). This study constitutes the southernmost records in the world and contributes to expanding the knowledge of the biodiversity of pathogenic fungi of spiders in Argentina.

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Spiders are predators that reduce insect pest populations in agroecosystems. In spite that the presence of spider assemblages has been described in different crop plants, no reports have been done for Citrus species in Argentina. We studied the spider community associated with cultures of Citrus sinensis in the province of Corrientes, Argentina, in two plots (AM1 irrigated and AM2 unirrigated) of 0.82 hectares each. Spiders were collected monthly by using pitfall traps, hand capture, agitation of foliage and sieving of soil litter. A total of 7174 specimens were collected (33 families, 44 genera and 200 species/morphospecies). The AM1 recorded 3811 individuals (33 families, 179 species/morphospecies) and AM2 3363 individuals (31 families, 174 species/morphospecies). November, December and January showed the highest abundance in both plots. A total of 70% of collected spiders were juveniles. Eight families were the most abundant and represented 75% of spiders collected in both plots, the largest being Lycosidae. We identified eight guilds in both plots, for which the ground runners resulted the most abundant (AM1 n = 1341, s=39, n=999 AM2, s = 33), followed by orb weavers (AM1 n = 637, s = 36; AM2 n = 552, s = 33), the stalkers (AM1 n = 471, s = 43, AM2 n = 453, s = 47) and the space web-builders (AM1 n = 446, s = 23; AM2 n = 342, s = 25). The analysis of alpha diversity in both plots (AM1H' = 4.161, J' = 0.802; AM2 H' = 4.184, J' = 0.811) showed no significant differences (t = 1.083 p = 0.279). The linear dependences model was the one with the best fit results, where the species observed were more than estimated. Clench model estimated 90.9% of the spiders observed in the unit with irrigation and 90.6% in the unit without irrigation.

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Spiders are predators that reduce insect pest populations in agroecosystems. In spite that the presence of spider assemblages has been described in different crop plants, no reports have been done for Citrus species in Argentina. We studied the spider community associated with cultures of Citrus sinensis in the province of Corrientes, Argentina, in two plots (AM1 irrigated and AM2 unirrigated) of 0.82 hectares each. Spiders were collected monthly by using pitfall traps, hand capture, agitation of foliage and sieving of soil litter. A total of 7 174 specimens were collected (33 families, 44 genera and 200 species/morphospecies). The AM1 recorded 3 811 individuals (33 families, 179 species/morphospecies) and AM2 3 363 individuals (31 families, 174 spe- cies/morphospecies). November, December and January showed the highest abundance in both plots. A total of 70% of collected spiders were juveniles. Eight families were the most abundant and represented 75% of spiders collected in both plots, the largest being Lycosidae. We identified eight guilds in both plots, for which the ground runners resulted the most abundant (AM1 n=1341, s=39, n=999 AM2, s=33), followed by orb weavers (AM1 n=637, s=36; AM2 n=552, s=33), the stalkers (AM1 n=471, s=43, AM2 n=453, s=47) and the space web- builders (AM1 n=446, s=23; AM2 n=342, s=25). The analysis of alpha diversity in both plots (AM1H’=4.161, J’=0.802; AM2 H’=4.184, J’=0.811) showed no significant differences (t=1.083 p=0.279). The linear dependences model was the one with the best fit results, where the species observed were more than estimated. Clench model estimated 90.9% of the spiders observed in the unit with irrigation and 90.6% in the unit without irrigation.

Las arañas son ideales como indicadores de cambios ecológicos por su diversidad y abundancia. En la provincia de Corrientes, Argentina, se estudiaron arañas de Citrus sinensis en parcelas de 0.82 hectáreas, con riego (AM1) y sin riego (AM2). Mediante pitfall, agitación de follaje, captura manual y tamizado de hojarasca se recolectaron 7 174 ejemplares (33 familias, 44 géneros y 200 especies/morfoespecies), el 70% fueron juveniles. AM1 registró 3 811 individuos (33 familias, 179 especies/morfoespecies) y AM2 3 363 (31 familias, 174 especies/morfoespecies). Durante el verano se observó la mayor abundancia. En ambas parcelas, ocho familias representaron el 75% del total, Lycosidae fue la más numerosa y se identificaron ocho gremios; las vagabundas de suelo fueron las más abundantes (AM1 n=1341, s=39; AM2 n=999, s=33) seguida por las constructoras de telas orbiculares (AM1 n=637, s=36; AM2 n=552, s=33), las cazadoras al acecho (AM1 n=471, s=43; AM2 n=453, s=47) y las de telas espaciales (AM1 n=446, s=23; AM2 n=342, s=25. La diversidad alfa en ambas parcelas (AM1 H’=4.161, J’=0.802; AM2 H’=4.184, J’=0.811) no mostró diferencias significativas (t=1.083, p=0.279). El modelo de dependencia lineal fue el que mejor ajustó los resultados. El modelo de Clench estimó el 90.9% de las observadas en AM1 y el 90.6% en la AM2.

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Soybean pest control in Argentina is done just by chemical control using broad-spectrum pesticides. Alpaida veniliae (Araneae, Araneidae) is one of the most abundant spider species of the orb web weaver guild in soybean, and it is considered a very important polyphagous predator, attacking different insects' families. The objective of this study was to determine if neurotoxic insecticides commonly used in soybean crops and a new active ingredient registered in Argentina (spinosad) adversely affected survival, prey consumption, mating behaviour, web building and reproductive capacity of A. veniliae females, under standard laboratory conditions. Spinosad was the most harmful insecticide due to high acute toxicity, even at lower concentrations than those registered for its field use and for its sublethal effects also. Cypermethrin caused several sublethal effects although its acute toxicity on spider was lower than other insecticides. It reduced prey consumption, affected web building, caused abnormalities in eggs sacs and decreased drastically the fecundity and fertility at sublethal concentrations. Endosulfan did not reduce prey consumption but it affected web building, caused abnormalities in eggs sacs and egg masses, and decreased the fecundity and fertility. Spinosad was also the compound with the most drastic effect on web building, it did not reduce prey consumption and fecundity, but fertility was reduced and abnormalities in egg sacs and egg masses were observed. The use of these insecticides in IPM programs according to their potential toxicity on spider communities is discussed.

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Exetasis jujuyensis Gillung sp. nov. (Acroceridae) is described from Argentina and a dichotomous key to species of Exetasis Walker is provided. Detailed observations are presented on the effect of fly larval development on the behavior of the host spider (Acanthoscurria sternalis Pocock (Theraphosidae)).

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Studies in transgenic soybean crops in Buenos Aires province, Argentina, revealed that Alpaida veniliae is one of the most abundant species in the guild of orb web spiders. This species is an effective natural enemy of insect pests affecting this crop. In the present study we carried out a descriptive and quantitative analysis of sexual behavior (courtship, mating and post-mating) of A. veniliae. The spiders were collected in transgenic soybean crops located in Chivilcoy (35 degrees 01' S - 60 degrees 06' W), Buenos Aires, Argentina, and reared under laboratory conditions. Based on observations of 20 couples (with virgin females), behavioral units of male and female in terms of postures and movements, including details on duration and frequency, were described at all stages of sexual activity (courtship, mating and post-mating). Courtship exhibited the greatest number and duration of behavioral units in both sexes. Male and female had a sequence of 16 and nine units, respectively, being the frequency of repetitions of the units significantly higher in the male. Mating was brief and males used a single palp to fill only one of the female spermathecae, after which the female became unreceptive. Mating had two behavioral units in the male and only one in the female. During post-mating males had three and females two behavioral units. The average duration of the whole sexual behavior was 541.90 +/- 123.1 seconds for the male and 338.20 +/- 74.1 seconds for the female. Alpaida veniliae females rarely accept a second mating with the same or another male (remating), indicating a strict monogamy. In 46% of observed mating, the female cannibalized the male after it. Females became unattractive after mating, since stop producing sex pheromones, causing a reduction of the male vibratory courtship. The high cost of courtship, including the risk of cannibalism, would reinforce the selectivity of males towards receptive virgin females.

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The diversity, abundance, spatial distribution, and phenology of the mygalomorph spider community in the "Ernesto Tornquist" Strict Nature Reserve were analyzed in this study. Located in southwestern Buenos Aires, Argentina, the Reserve is representative of the Ventania system, which is a sigmoidal mountain belt 180 km in length. This exceptional hilly ecosystem is home for many endemic species and rich native fauna and flora. Spider abundance was sampled monthly from October 2009 to October 2010 by hand capture and pitfall traps on grassland slopes. The species recorded in the study area were: Actinopus sp.1 (Actinopodidae); Grammostola vachoni and Plesiopelma longisternale (Theraphosidae); Acanthogonatus centralis (Nemesiidae); and Mecicobothrium thorelli (Mecicobothriidae). Grammostola vachoni and Acanthogonatus centralis were the dominant species in hand capture and pitfall traps, respectively. The seasonal variation, diversity, and abundance of the mygalomorph community are analyzed and discussed here. The Mygalomorphae of the Ventania system comprises an important group of sedentary and cryptozoic spiders that seem to be highly dependent on habitat type and environmental factors.

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Studies in transgenic soybean crops in Buenos Aires province, Argentina, revealed that Alpaida veniliae is one of the most abundant species in the guild of orb web spiders. This species is an effective natural enemy of insect pests affecting this crop. In the present study we carried out a descriptive and quantitative analysis of sexual behavior (courtship, mating and post-mating) of A. veniliae. The spiders were collected in transgenic soybean crops located in Chivilcoy (35º01’ S - 60º06’ W), Buenos Aires, Argentina, and reared under laboratory conditions. Based on observations of 20 couples (with virgin females), behavioral units of male and female in terms of postures and movements, including details on duration and frequency, were described at all stages of sexual activity (courtship, mating and post-mating). Courtship exhibited the greatest number and duration of behavioral units in both sexes. Male and female had a sequence of 16 and nine units, respectively, being the frequency of repetitions of the units significantly higher in the male. Mating was brief and males used a single palp to fill only one of the female spermathecae, after which the female became unreceptive. Mating had two behavioral units in the male and only one in the female. During post-mating males had three and females two behavioral units. The average duration of the whole sexual behavior was 541.90±123.1 seconds for the male and 338.20±74.1 seconds for the female. Alpaida veniliae females rarely accept a second mating with the same or another male (remating), indicating a strict monogamy. In 46% of observed mating, the female cannibalized the male after it. Females became unattractive after mating, since stop producing sex pheromones, causing a reduction of the male vibratory courtship. The high cost of courtship, including the risk of cannibalism, would reinforce the selectivity of males towards receptive virgin females.

Estudios realizados en cultivos de soja transgénica en la provincia de Buenos Aires, Argentina, revelaron que Alpaida veniliae es una de las especies más abundantes dentro del gremio de arañas orbiculares. Esta especie es un eficaz enemigo natural de las plagas de insectos de este cultivo. En el presente estudio se llevó a cabo un análisis descriptivo y cuantitativo de la conducta sexual (cortejo, cópula y post-cópula) de A. veniliae. Las arañas fueron recolectadas en cultivos de soja transgénica ubicados en Chivilcoy (35º01’ S - 60º06’ W), (Buenos Aires, Argentina) y criadas en condiciones de laboratorio. A partir de la formación de 20 parejas (con hembras vírgenes), se observaron las unidades de comportamiento de machos y hembras, en términos de posturas y movimientos, incluyendo los detalles de su duración y frecuencia en todas las etapas del apareamiento. El cortejo exhibió el mayor número y la mayor duración de las unidades de comportamiento en ambos sexos. La secuencia de unidades fue 16 en el macho y nueve en la hembra, siendo la frecuencia de repeticiones de las unidades significativamente mayor en el macho. La cópula fue breve y el macho usó un solo palpo transfiriendo esperma a una sola espermateca de la hembra. Hubo dos unidades de comportamiento en el macho y una en la hembra. Durante la post-cópula el macho tuvo tres y la hembra dos unidades de comportamiento. La duración media de todo el comportamiento sexual fue 541.90±123.1 segundos para el macho y 338.20±74.1 segundos para la hembra. La hembra de A. veniliae sólo excepcionalmente aceptó una segunda cópula con el mismo u otro macho, lo que indica una monogamia estricta. En el 46% de las cópulas observadas la hembra canibalizó al macho al terminar la misma. Debido a que a partir de este momento dejan de producir feromonas sexuales, se vuelven no receptivas y provocan una reducción del cortejo del macho. El alto costo del cortejo del macho, incluyendo el riesgo de canibalismo, reforzaría la selectividad de éstos hacia las hembras receptivas vírgenes.

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Arachnofauna (Araneae: Araneae) in transgenic and conventional cotton crops (Gossypiumhirsutum) in the North of Santa Fe, Argentina. Spiders have considerable potential importance for their role as predators to some pests in agricultural systems. The composition of spiders in transgenic and conventional cotton at the Research Station of INTA Reconquista (Santa Fe) was studied during the 2005-2006 season. The experiment was a complete randomized block design with three replications and three treatments: transgenic Bt cotton (ALBt), conventional cotton without chemical control (ALCSC), and conventional cotton with chemical control (ALCCC). Weekly, spiders were collected using nets, vertical cloth and pitfall-traps. A total of 1 255 specimens (16 families, and 32 species) were collected. Seven families were found in all the treatments, mainly Thomisidae (n=1 051, 84.04%) and Araneidae (n=83, 6.64%). The Hunting spiders guild ambushers (n=1 053, 83.91%), “Orb weavers” (n=85, 6.77%) and “Stalkers” (n=53, 4.22%) were more abundant. There were no significant differences in the indexes diversity between treatments. Spiders were presented during the whole crop season, with peaks about flowering and boll maturity, with the highest abundance in ALBt. This work is part of the first set of data registered in Argentina about spider’s community in cotton crops. Rev. Biol. Trop. 60 (2): 611-623. Epub 2012 June 01.

Las arañas tienen un valor potencial considerable por su rol depredador de insectos, estas son plagas de la agricultura. Durante la campaña agrícola 2005/06, en INTA Reconquista, Santa Fe (Argentina) se estudio la composición de arañas presentes en cultivos de algodón transgénico y convencional, mediante un diseño experimental de bloques completos al azar, con tres repeticiones y tres tratamientos: algodón transgénico Bt (ALBt), algodón convencional sin control químico (ALCSC) y con control químico (ALCCC). Semanalmente, se capturaron arañas, con una red entomológica de arrastre, paño vertical de 1m y trampas de caída. Asimismo se recolectaron 1 255 ejemplares (16 familias y 32 especies). Siete familias se presentaron en los tres tratamientos, donde predomino Thomisidae (n=1 051, 84.04%) y Araneidae (n=83, 6.64%). El gremio cazadoras por emboscada (n=1 053, 83.91%), “Tejedoras de telas orbiculares” (n=85, 6.77%) y “Cazadoras al acecho” (n=53, 4.22%) fueron las más abundantes. No hubo diferencias significativas en los índices de diversidad entre tratamientos. Las arañas se presentaron durante todo el ciclo del cultivo, con picos en las semanas de floración y madurez de las capsulas, además la mayor abundancia la encontramos en el ALBt. Este trabajo constituye el primer registro sobre la comunidad de arañas en cultivos de algodón para Argentina.

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Spiders have considerable potential importance for their role as predators to some pests in agricultural systems. The composition of spiders in transgenic and conventional cotton at the Research Station of INTA Reconquista (Santa Fe) was studied during the 2005-2006 season. The experiment was a complete randomized block design with three replications and three treatments: transgenic Bt cotton (ALBt), conventional cotton without chemical control (ALCSC), and conventional cotton with chemical control (ALCCC). Weekly, spiders were collected using nets, vertical cloth and pitfall-traps. A total of 1255 specimens (16 families, and 32 species) were collected. Seven families were found in all the treatments, mainly Thomisidae (n=1 51, 84.04%) and Araneidae (n=83, 6.64%). The Hunting spiders guild ambushers (n=1053, 83.91%), "Orb weavers" (n=85, 6.77%) and "Stalkers" (n=53, 4.22%) were more abundant. There were no significant differences in the indexes diversity between treatments. Spiders were presented during the whole crop season, with peaks about flowering and boll maturity, with the highest abundance in ALBt. This work is part of the first set of data registered in Argentina about spider's community in cotton crops.

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Effect of spiders (Arachnida: Araneae) as predators of insect pest in alfalfa crops (Medicago sativa) (Fabaceae) in Argentina. Spiders are predators that reduce insect pest populations in agroecosystems. Trials were conducted to measure the selectivity against different insect preys, the daily consumption, effect of predators alone and together with a known number of preys, and the indirect effect of predators on vegetation. For this, experimental units (1x1m) were used covered with a fine plastic mesh. Misumenops pallidus, Oxyopes salticus and Araneus sp. were used as generalist predators, and aphids, weevils, locusts, chrysomelids and Lepidoptera larvae as their potential preys. Among the preys offered, the spiders preferred Lepidoptera larvae compared to the other two pests groups (weevils and aphids). The maximum consumption rate was of 93.33% for Lepidoptera larvae, 25.33% for aphids and 11.67% for weevils. The Q Index values for the three species of spiders showed a positive selectivity only for defoliating larvae. O. salticus showed the highest values of consumption rates while Rachiplusia nu was the most consumed. The maximum value of consumption in 24 hours was showed by O. salticus on R. nu (C)=2.8. The association of several species of predatory spiders increased the total number of insects captured, and also showed that the addition of spiders caused a decrease in the number of leaves damaged by the effect of lepidopterous larvae. Rev. Biol. Trop. 59 (4): 1651-1662. Epub 2011 December 01.

Las arañas son depredadoras capaces de reducir las poblaciones de insectos plaga en agroecosistemas. Para medir la selectividad frente a distintas presas, se realizaron ensayos de consumo diario, efecto de los depredadores aisladamente y en conjunto sobre el número de presas y efecto indirecto de los depredadores sobre la vegetación; se utilizaron jaulas experimentales de 1x1m cubiertas con una fina malla plástica. Misumenops pallidus, Oxyopes salticus y Araneus sp. fueron utilizadas como depredadores generalistas, áfidos gorgojos, larvas de lepidópteras, crisomélidos y ortópteros como sus presas potenciales. Las arañas prefirieron larvas de lepidópteros frente a curculiónidos y áfidos. El consumo máximo de larvas de lepidópteros fue de 93.33%, áfidos 25.33% y curculiónidos 11.67%. El Índice Q para las tres especies de arañas demostró una selectividad positiva sólo para las larvas defoliadoras. O. salticus presentó las tasas de consumo mayores. Rachiplusia nu fue la especie más consumida. El valor máximo de consumo registrado en 24h fue para O. salticus frente a R. nu (C)=2.8. La asociación de varias especies de arañas depredadoras incrementó el total de insectos capturados. La presencia de arañas provocó la disminución del número de hojas dañadas por el efecto de las larvas de lepidópteros plaga.

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Spiders are predators that reduce insect pest populations in agroecosystems. Trials were conducted to measure the selectivity against different insect preys, the daily consumption, effect of predators alone and together with a known number of preys, and the indirect effect of predators on vegetation. For this, experimental units (1 x 1m) were used covered with a fine plastic mesh. Misumenops pallidus, Oxyopes salticus and Araneus sp. were used as generalist predators, and aphids, weevils, locusts, chrysomelids and Lepidoptera larvae as their potential preys. Among the preys offered, the spiders preferred Lepidoptera larvae compared to the other two pests groups (weevils and aphids). The maximum consumption rate was of 93.33% for Lepidoptera larvae, 25.33% for aphids and 11.67% for weevils. The Q Index values for the three species of spiders showed a positive selectivity only for defoliating larvae. O. salticus showed the highest values of consumption rates while Rachiplusia nu was the most consumed. The maximum value of consumption in 24 hours was showed by O. salticus on R. nu (C) = 2.8. The association of several species of predatory spiders increased the total number of insects captured, and also showed that the addition of spiders caused a decrease in the number of leaves damaged by the effect of lepidopterous larvae.

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Over the last decades there has been an increasing interest in the use of natural enemies to control pest insects, including spiders. We studied a spider community in Argentina by sampling every two weeks during 2004-2006 in one-hectare lots. Soil stratum spiders were collected using nets and pitfall traps. A total of 6229 specimens were collected (15 families and 50 species). Seven families were found in the herbal stratum, the most abundant were Thomisidae (n=2012, 32.30%), Araneidae (n=1516, 24.33%) and Oxyopidae (n=604, 9.70%). The soil had 14 families, mainly: Lycosidae (n=629, 10.10%) and Linyphiidae (n=427, 6.85%). Hunting spiders predominated: ambushers (32.99%); stalkers (11.77%) and ground-runners (10.84%) were less common. The most abundant web building spiders were the orb weavers (27.56%). The diversity indexes were: H'=2.97, Dsp=0.11 and J=0.79, evidencing a moderately diverse spider community with predominance of Misumenops pallidus, Oxyopes salticus, Lycosa poliostoma and L. erythrognatha. The spiders were present throughout the phenological development of the crop with abundance peaks in spring and summer.

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Spider community (Arachnida, Araneae) of alfalfa crops (Medicago sativa) in Buenos Aires, Argentina. Over the last decades there has been an increasing interest in the use of natural enemies to control pest insects, including spiders. We studied a spider community in Argentina by sampling every two weeks during 2004-2006 in one-hectare lots. Soil stratum spiders were collected using nets and pitfall traps. A total of 6229 specimens were collected (15 families and 50 species). Seven families were found in the herbal stratum, the most abundant were Thomisidae (n=2012, 32.30%), Araneidae (n=1516, 24.33%) and Oxyopidae (n=604, 9.70%). The soil had 14 families, mainly: Lycosidae (n=629, 10.10%) and Linyphiidae (n=427, 6.85%). Hunting spiders predominated: ambushers (32.99 %); stalkers (11.77%) and ground-runners (10.84%) were less common. The most abundant web building spiders were the orb weavers (27.56%). The diversity indexes were: H´=2.97, Dsp=0.11 and J=0.79, evidencing a moderately diverse spider community with predominance of Misumenops pallidus, Oxyopes salticus, Lycosa poliostoma and L. erythrognatha. The spiders were present throughout the phenological development of the crop with abundance peaks in spring and summer. Rev. Biol. Trop. 58 (2): 757-767. Epub 2010 June 02.

En las últimas décadas se ha dado un interés creciente en el uso de enemigos naturales para controlar plagas de insectos, como arañas. Se estudió una comunidad de arañas en Argentina mediante un muestreo cada dos semanas durante el periodo 2004-2006 en lotes de una hectárea. En el estrato del suelo las arañas fueron colectadas con redes de arrastre y trampas de caída. Se recolecto un total de 6 229 ejemplares (15 familias y 50 especies). Siete familias se encuentran en el estrato herbáceo, las más abundantes fueron: Thomisidae (n=2 012, 32.30%), Araneidae (n=1 516, 24.33%) y Oxyopidae (n=604, 9.70%). El suelo habían 14 familias, principalmente: Lycosidae (n=629, 10.10%) y Linyphiidae (n=427, 6.85%). Predominaron las arañas cazadoras: por emboscadas (32.99%), al acecho (11.77%), corredoras de suelo (10.84%) y tejedoras orbiculares (27.56%). Los índices de diversidad fueron: H´=2.97, Dsp=0.11 y J=0.79, evidenciando una comunidad de arañas moderadamente diversa, con predominio de Misumenops pallidus, Oxyopes salticus, Lycosa poliostoma and L. erythrognatha. Las arañas estuvieron presentes durante el desarrollo fenológico del cultivo con picos de abundancia en primavera y verano.

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Spiders (Arachnida: Araneae) associated with two degraded forests in the humid Chaco of Corrientes, Argentina. The advancing degradation of the forest in the biogeographic Chaco province (Argentina) produces an important loss of its little known biodiversity. We studied the spider biodiversity in two forests of Corrientes, Argentina’s "Distrito Oriental Húmedo del Chaco": Laguna Brava and El Perichón. Seasonal samplings of foliage and fallen leaves between 2001 and 2002 produced 2 067 individuals from 33 families and 226 species/ morphospecies). The families Araneidae, Anyphaenidae, Salticidae and Theridiidae were the most abundant in both forests. The "orb weavers" guild had the highest number of specimens (n=382) and "stalkers" the highest richness (S=56). in Brava, highest abundance was in the summer (n=287) and spring (n=273), in Perichón, it was in winter (n=315). The specific richness and the diversity indexes were higher in Brava (S=134, H´=4.23, E=0.86, D=0.023) than in Perichón (S=127, H´=4.08, E=0.84, D=0.029). The similarity value between both forests was MH=0.611. Rev. Biol. Trop. 55 (3-4): 899-909. Epub 2007 December, 28.

El importante avance de la degradación de bosques en la Provincia Biogeográfica del Chaco, Argentina, conlleva una pérdida importante de su poco conocida biodiversidad. Se realizó un estudio de la fauna de arañas en dos bosques de la provincia de Corrientes, Argentina, correspondientes al Distrito Oriental Húmedo del Chaco, en las localidades de Laguna Brava y El Perichón. Se realizaron muestreos estacionales entre los años 2001 y 2002. Las arañas recolectadas (2 067 individuos de 33 familias y 226 especies/morfoespecies) fueron obtenidas por golpeteo del estrato arbustivo y tamizado de hojarasca. Las familias Araneidae, Anyphaenidae, Salticidae y Theridiidae fueron las más abundantes en los dos bosques. El gremio de arañas "constructoras de telas orbiculares" presentó el mayor número de individuos (n=382) y el de "cazadoras al acecho" la mayor riqueza (S=56). En Laguna Brava se observó mayor abundancia en el verano (n=287) y primavera (n=273) y en el Perichón en invierno (n=315). La riqueza específica y el valor de los índices de diversidad, fueron mayores en Laguna Brava (S=134, H´=4.23, E=0.86, D=0.023) que en El Perichón (S=127, H´=4.08, E=0.84, D=0.029). La similitud entre ambos bosques fue MH=0.611.

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