Effect of the insecticide Lambda-cyhalothrin on rice spider populations in southern Brazil

The adverse effect that insecticides have on spider populations is of major concern since these predators are a component in the biological control of rice insect pest populations. This study was designed to determine the effect of the pyrethroid insecticide, Lambda-cyhalothrin, on spider populations in rice fields. Treatments consisted of plots treated once with the insecticide and untreated plots (control). Spiders were sampled four times per crop year over a two year period in each of three sites in the state of Rio Grande dol Sul, Brazil. Treatments were replicated four times. Sweep net sampling was conducted to sample the araneofauna. Overall 1,961 spiders were collected, with a predominance of juveniles over adults. Between treatments, there were significantly larger numbers of spiders and species richness in areas without insecticide. There were also significant differences among areas (sites) and among days after the insecticide application. Of the 12 recorded families, Araneidae and Tetragnathidae dominated, and were both strongly affected by insecticide application, decreasing more than 50% in those locations. Overall, 37 species were recorded (insecticide: 29; without: 26), eleven species were exclusive for rice without insecticide and eight for rice with insecticide. Alpaida veniliae (Keyserling, 1865) (n = 236) and Tetragnathaaff.jaculator (108) were the most abundant in both treatments, but with large decreases in abundance in rice with insecticide. Among guilds, the predominance was for orb weavers (67.3%) in all locations, but with much lower values for those spiders in rice with insecticide application. This study illustrates that the spider fauna in rice fields are adversely affected by the application of the insecticide Lambda-cyhalothrin.

Effect of the insecticide Lambda-cyhalothrin on rice spider populations in southern Brazil

The adverse effect that insecticides have on spider populations is of major concern since these predators are a component in the biological control of rice insect pest populations. This study was designed to determine the effect of the pyrethroid insecticide, Lambda-cyhalothrin, on spider populations in rice fields. Treatments consisted of plots treated once with the insecticide and untreated plots (control). Spiders were sampled four times per crop year over a two year period in each of three sites in the state of Rio Grande dol Sul, Brazil. Treatments were replicated four times. Sweep net sampling was conducted to sample the araneofauna. Overall 1,961 spiders were collected, with a predominance of juveniles over adults. Between treatments, there were significantly larger numbers of spiders and species richness in areas without insecticide. There were also significant differences among areas (sites) and among days after the insecticide application. Of the 12 recorded families, Araneidae and Tetragnathidae dominated, and were both strongly affected by insecticide application, decreasing more than 50% in those locations. Overall, 37 species were recorded (insecticide: 29; without: 26), eleven species were exclusive for rice without insecticide and eight for rice with insecticide. Alpaida veniliae (Keyserling, 1865) (n = 236) and Tetragnathaaff.jaculator (108) were the most abundant in both treatments, but with large decreases in abundance in rice with insecticide. Among guilds, the predominance was for orb weavers (67.3%) in all locations, but with much lower values for those spiders in rice with insecticide application. This study illustrates that the spider fauna in rice fields are adversely affected by the application of the insecticide Lambda-cyhalothrin.

Effect of the insecticide Lambda-cyhalothrin on rice spider populations in southern Brazil

The adverse effect that insecticides have on spider populations is of major concern since these predators are a component in the biological control of rice insect pest populations. This study was designed to determine the effect of the pyrethroid insecticide, Lambda-cyhalothrin, on spider populations in rice fields. Treatments consisted of plots treated once with the insecticide and untreated plots (control). Spiders were sampled four times per crop year over a two year period in each of three sites in the state of Rio Grande dol Sul, Brazil. Treatments were replicated four times. Sweep net sampling was conducted to sample the araneofauna. Overall 1,961 spiders were collected, with a predominance of juveniles over adults. Between treatments, there were significantly larger numbers of spiders and species richness in areas without insecticide. There were also significant differences among areas (sites) and among days after the insecticide application. Of the 12 recorded families, Araneidae and Tetragnathidae dominated, and were both strongly affected by insecticide application, decreasing more than 50% in those locations. Overall, 37 species were recorded (insecticide: 29; without: 26), eleven species were exclusive for rice without insecticide and eight for rice with insecticide. Alpaida veniliae (Keyserling, 1865) (n = 236) and Tetragnathaaff.jaculator (108) were the most abundant in both treatments, but with large decreases in abundance in rice with insecticide. Among guilds, the predominance was for orb weavers (67.3%) in all locations, but with much lower values for those spiders in rice with insecticide application. This study illustrates that the spider fauna in rice fields are adversely affected by the application of the insecticide Lambda-cyhalothrin.

Effect of the insecticide Lambda-cyhalothrin on rice spider populations in southern Brazil

The adverse effect that insecticides have on spider populations is of major concern since these predators are a component in the biological control of rice insect pest populations. This study was designed to determine the effect of the pyrethroid insecticide, Lambda-cyhalothrin, on spider populations in rice fields. Treatments consisted of plots treated once with the insecticide and untreated plots (control). Spiders were sampled four times per crop year over a two year period in each of three sites in the state of Rio Grande dol Sul, Brazil. Treatments were replicated four times. Sweep net sampling was conducted to sample the araneofauna. Overall 1,961 spiders were collected, with a predominance of juveniles over adults. Between treatments, there were significantly larger numbers of spiders and species richness in areas without insecticide. There were also significant differences among areas (sites) and among days after the insecticide application. Of the 12 recorded families, Araneidae and Tetragnathidae dominated, and were both strongly affected by insecticide application, decreasing more than 50% in those locations. Overall, 37 species were recorded (insecticide: 29; without: 26), eleven species were exclusive for rice without insecticide and eight for rice with insecticide. Alpaida veniliae (Keyserling, 1865) (n = 236) and Tetragnathaaff.jaculator (108) were the most abundant in both treatments, but with large decreases in abundance in rice with insecticide. Among guilds, the predominance was for orb weavers (67.3%) in all locations, but with much lower values for those spiders in rice with insecticide application. This study illustrates that the spider fauna in rice fields are adversely affected by the application of the insecticide Lambda-cyhalothrin.

Effect of the insecticide Lambda-cyhalothrin on rice spider populations in southern Brazil

The adverse effect that insecticides have on spider populations is of major concern since these predators are a component in the biological control of rice insect pest populations. This study was designed to determine the effect of the pyrethroid insecticide, Lambda-cyhalothrin, on spider populations in rice fields. Treatments consisted of plots treated once with the insecticide and untreated plots (control). Spiders were sampled four times per crop year over a two year period in each of three sites in the state of Rio Grande dol Sul, Brazil. Treatments were replicated four times. Sweep net sampling was conducted to sample the araneofauna. Overall 1,961 spiders were collected, with a predominance of juveniles over adults. Between treatments, there were significantly larger numbers of spiders and species richness in areas without insecticide. There were also significant differences among areas (sites) and among days after the insecticide application. Of the 12 recorded families, Araneidae and Tetragnathidae dominated, and were both strongly affected by insecticide application, decreasing more than 50% in those locations. Overall, 37 species were recorded (insecticide: 29; without: 26), eleven species were exclusive for rice without insecticide and eight for rice with insecticide. Alpaida veniliae (Keyserling, 1865) (n = 236) and Tetragnathaaff.jaculator (108) were the most abundant in both treatments, but with large decreases in abundance in rice with insecticide. Among guilds, the predominance was for orb weavers (67.3%) in all locations, but with much lower values for those spiders in rice with insecticide application. This study illustrates that the spider fauna in rice fields are adversely affected by the application of the insecticide Lambda-cyhalothrin.

On the Neotropical genus Cybaeodamus (Araneae, Zodariidae, Storeninae)

Four new species of the spider genus Cybaeodamus Mello-Leitão, 1938 are described and illustrated: C. meridionalis sp. nov. from Brazil and Argentina, C. taim sp. nov. from Brazil, Argentina and Uruguay, C. brescoviti sp. nov. and C. tocantins sp. nov. from setentrional region of Brazil. For the species Cybaeodamus enigmaticus (Mello-Leitão, 1939), C. lycosoides (Nicolet, 1849) and C. ornatus Mello-Leitão, 1938, new illustrations based on the examination of the types are presented. The species Cybaeodamus nigrovittatus Mello-Leitão, 1941 which the holotype is an immature specimen, C. pallidus (Mello-Leitão, 1943) which the type was not located, C. rastellifer (Mello-Leitão, 1940) and C. scottae Mello-Leitão, 1941, both described upon juvenile specimens, all from Argentina, are considered as species inquirendae.

Neste trabalho são descritas e ilustradas quatro espécies novas do gênero Cybaeodamus Mello-Leitão, 1938: C. meridionalis sp. nov. do Brasil e Argentina, C. taim sp. nov. do Brasil, Argentina e Uruguai, C. brescoviti sp. nov. e C. tocantins sp. nov. do Brasil setentrional. Para as espécies Cybaeodamus enigmaticus (Mello-Leitão, 1939), C. lycosoides (Nicolet, 1849) e C. ornatus Mello-Leitão, 1938 são apresentadas novas ilustrações a partir do exame do material-tipo. As espécies Cybaeodamus nigrovittatus Mello-Leitão, 1941 cujo holótipo é um indivíduo jovem, C. pallidus (Mello-Leitão, 1943) da qual o tipo não foi localizado, C. rastellifer (Mello-Leitão, 1940) e C. scottae Mello-Leitão, 1941, ambas com tipos juvenis, todas da Argentina, são consideradas species inquirendae.

On the Neotropical genus Cybaeodamus (Araneae, Zodariidae, Storeninae)

Four new species of the spider genus Cybaeodamus Mello-Leitão, 1938 are described and illustrated: C. meridionalis sp. nov. from Brazil and Argentina, C. taim sp. nov. from Brazil, Argentina and Uruguay, C. brescoviti sp. nov. and C. tocantins sp. nov. from setentrional region of Brazil. For the species Cybaeodamus enigmaticus (Mello-Leitão, 1939), C. lycosoides (Nicolet, 1849) and C. ornatus Mello-Leitão, 1938, new illustrations based on the examination of the types are presented. The species Cybaeodamus nigrovittatus Mello-Leitão, 1941 which the holotype is an immature specimen, C. pallidus (Mello-Leitão, 1943) which the type was not located, C. rastellifer (Mello-Leitão, 1940) and C. scottae Mello-Leitão, 1941, both described upon juvenile specimens, all from Argentina, are considered as species inquirendae.

Neste trabalho são descritas e ilustradas quatro espécies novas do gênero Cybaeodamus Mello-Leitão, 1938: C. meridionalis sp. nov. do Brasil e Argentina, C. taim sp. nov. do Brasil, Argentina e Uruguai, C. brescoviti sp. nov. e C. tocantins sp. nov. do Brasil setentrional. Para as espécies Cybaeodamus enigmaticus (Mello-Leitão, 1939), C. lycosoides (Nicolet, 1849) e C. ornatus Mello-Leitão, 1938 são apresentadas novas ilustrações a partir do exame do material-tipo. As espécies Cybaeodamus nigrovittatus Mello-Leitão, 1941 cujo holótipo é um indivíduo jovem, C. pallidus (Mello-Leitão, 1943) da qual o tipo não foi localizado, C. rastellifer (Mello-Leitão, 1940) e C. scottae Mello-Leitão, 1941, ambas com tipos juvenis, todas da Argentina, são consideradas species inquirendae.

Fauna de aranhas (Arachnida, Araneae) em diferentes estágios do cultivo do arroz irrigado em Cachoeirinha, RS, Brasil

The spider diversity associated to a rice field was surveyed along different stages of the culture. The studied area belongs to the Estação Experimental do Arroz (EEA), Instituto Rio Grandense do Arroz (IRGA), Cachoeirinha, state of Rio Grande do Sul, Brazil (50º58'21"W; 29º55'30"S). Between October 2004 and June 2005, 17 samples were taken, distributed in three periods: before seeding, during the development of the rice plants and after the harvest. Samples were done in the morning using sweeping nets (35 cm diameter), 50 sweeps in each of four randomly chosen transects. A total of 918 spiders were sampled, distributed in 14 families, mostly Araneidae, Anyphaenidae, Oxyopidae and Tetragnathidae. Among the adults, 38 morphospecies were found, the most abundant were Alpaida veniliae (Keyserling, 1865), Tetragnatha nitens (Audouin, 1826), Ashtabula sp.1 and Tetragnatha aff. jaculator, the four together comprising more than 45% of the adult specimens. Of the species richness estimators used, Chao 1 was closer to the observed richness; 87,4% of the potentially present species were effectively sampled. Both abundance and species richness showed an increasing trend, accompanying rice development (and thus increasing habitat complexity), with a stern decrease after harvesting. A constant colonization of the habitat is thus postulated, also given the high number of young spiders found at all times. There were no significant correlations between climatic factors (temperature and rainfall) and neither abundance nor species richness, except a positive one between rainfall and richness. Among the functional groups, ambushing hunters dominated, followed by orb-web builders. An analysis of similarity (ANOSIM) found significant differences among the fauna of the three evaluated periods. Thus, system disturbance, in the form of rice sowing and harvesting, brutally altering environmental structure, leads to strong spider diversity changes both in terms of species richness and species composition. The results suggest biodiversity studies in agroecosystems can help us understand not only applied but also basic problems.

Com a intenção de conhecer a diversidade da araneofauna relacionada à cultura do arroz, foi realizado um inventário deste agroecossistema ainda pouco estudado em sua biodiversidade. Foram realizadas 17 amostragens na Estação Experimental do Arroz (EEA), do Instituto Rio Grandense do Arroz (IRGA), Cachoeirinha, RS (50º58'21"W; 29º55'30"S) entre outubro de 2004 e junho de 2005, em três períodos: antes do arroz ser semeado, durante o desenvolvimento do arroz e após a colheita. As coletas foram efetuadas no período matinal utilizando rede-de-varredura (35 cm de diâmetro), 50 golpes em cada um dos quatro transectos por amostragem. Coletou-se um total de 918 aranhas distribuídas em 14 famílias, com predomínio de Araneidae, Anyphaenidae, Oxyopidae e Tetragnathidae. Entre os indivíduos adultos, foram determinadas 38 morfoespécies, as mais abundantes Alpaida veniliae (Keyserling, 1865), Tetragnatha nitens (Audouin, 1826), Ashtabula sp.1 e Tetragnatha aff. jaculator, as quatro juntas com mais de 45% dos espécimes adultos coletados. Dos estimadores de riqueza de espécies utilizados, o que mais se aproximou da riqueza observada foi Chao 1; segundo este, 87,4% das espécies potencialmente presentes foram amostradas. Os resultados demonstraram que tanto abundância como riqueza tiveram a tendência ao crescimento, acompanhando o desenvolvimento da lavoura de arroz. Uma constante colonização no hábitat foi constatada dado o alto número de aranhas jovens encontradas em todos os períodos. Não foram encontradas diferenças significativas para a correlação entre dados abióticos (temperatura e pluviosidade) com a abundância e a riqueza, exceto pluviosidade vs. riqueza. Entre os grupos funcionais, houve o predomínio das caçadoras emboscadoras, seguido das construtoras de teias orbiculares. A análise de similaridade (ANOSIM) encontrou diferenças significativas entre a fauna dos três períodos avaliados. Assim, a perturbação na forma como o arroz é semeado e colhido altera a estrutura ambiental brutalmente, conduzindo a uma mudança na diversidade de aranhas em termos de riqueza e composição de espécies. Os resultados sugerem a importância de estudos da biodiversidade nos agroecossistemas.

Fauna de aranhas (Arachnida, Araneae) em diferentes estágios do cultivo do arroz irrigado em Cachoeirinha, RS, Brasil

The spider diversity associated to a rice field was surveyed along different stages of the culture. The studied area belongs to the Estação Experimental do Arroz (EEA), Instituto Rio Grandense do Arroz (IRGA), Cachoeirinha, state of Rio Grande do Sul, Brazil (50º58'21"W; 29º55'30"S). Between October 2004 and June 2005, 17 samples were taken, distributed in three periods: before seeding, during the development of the rice plants and after the harvest. Samples were done in the morning using sweeping nets (35 cm diameter), 50 sweeps in each of four randomly chosen transects. A total of 918 spiders were sampled, distributed in 14 families, mostly Araneidae, Anyphaenidae, Oxyopidae and Tetragnathidae. Among the adults, 38 morphospecies were found, the most abundant were Alpaida veniliae (Keyserling, 1865), Tetragnatha nitens (Audouin, 1826), Ashtabula sp.1 and Tetragnatha aff. jaculator, the four together comprising more than 45% of the adult specimens. Of the species richness estimators used, Chao 1 was closer to the observed richness; 87,4% of the potentially present species were effectively sampled. Both abundance and species richness showed an increasing trend, accompanying rice development (and thus increasing habitat complexity), with a stern decrease after harvesting. A constant colonization of the habitat is thus postulated, also given the high number of young spiders found at all times. There were no significant correlations between climatic factors (temperature and rainfall) and neither abundance nor species richness, except a positive one between rainfall and richness. Among the functional groups, ambushing hunters dominated, followed by orb-web builders. An analysis of similarity (ANOSIM) found significant differences among the fauna of the three evaluated periods. Thus, system disturbance, in the form of rice sowing and harvesting, brutally altering environmental structure, leads to strong spider diversity changes both in terms of species richness and species composition. The results suggest biodiversity studies in agroecosystems can help us understand not only applied but also basic problems.

Com a intenção de conhecer a diversidade da araneofauna relacionada à cultura do arroz, foi realizado um inventário deste agroecossistema ainda pouco estudado em sua biodiversidade. Foram realizadas 17 amostragens na Estação Experimental do Arroz (EEA), do Instituto Rio Grandense do Arroz (IRGA), Cachoeirinha, RS (50º58'21"W; 29º55'30"S) entre outubro de 2004 e junho de 2005, em três períodos: antes do arroz ser semeado, durante o desenvolvimento do arroz e após a colheita. As coletas foram efetuadas no período matinal utilizando rede-de-varredura (35 cm de diâmetro), 50 golpes em cada um dos quatro transectos por amostragem. Coletou-se um total de 918 aranhas distribuídas em 14 famílias, com predomínio de Araneidae, Anyphaenidae, Oxyopidae e Tetragnathidae. Entre os indivíduos adultos, foram determinadas 38 morfoespécies, as mais abundantes Alpaida veniliae (Keyserling, 1865), Tetragnatha nitens (Audouin, 1826), Ashtabula sp.1 e Tetragnatha aff. jaculator, as quatro juntas com mais de 45% dos espécimes adultos coletados. Dos estimadores de riqueza de espécies utilizados, o que mais se aproximou da riqueza observada foi Chao 1; segundo este, 87,4% das espécies potencialmente presentes foram amostradas. Os resultados demonstraram que tanto abundância como riqueza tiveram a tendência ao crescimento, acompanhando o desenvolvimento da lavoura de arroz. Uma constante colonização no hábitat foi constatada dado o alto número de aranhas jovens encontradas em todos os períodos. Não foram encontradas diferenças significativas para a correlação entre dados abióticos (temperatura e pluviosidade) com a abundância e a riqueza, exceto pluviosidade vs. riqueza. Entre os grupos funcionais, houve o predomínio das caçadoras emboscadoras, seguido das construtoras de teias orbiculares. A análise de similaridade (ANOSIM) encontrou diferenças significativas entre a fauna dos três períodos avaliados. Assim, a perturbação na forma como o arroz é semeado e colhido altera a estrutura ambiental brutalmente, conduzindo a uma mudança na diversidade de aranhas em termos de riqueza e composição de espécies. Os resultados sugerem a importância de estudos da biodiversidade nos agroecossistemas.

Aranhas da família Theridiosomatidae: espécie nova e novas ocorrências no Brasil

Theridiosoma caaguara sp. nov. from Rio Grande do Sul state, Brazil, is described and illustrated. Baalzebub baubo Coddington, 1986 is recorded for the first time for Brazil and the known geographic distribution of Epilineutes globosus (O. P.-Cambridge, 1896), Naatlo splendida (Taczanowski, 1873) and Ogulnius obtectus O. P.-Cambridge, 1882 is extended.

Theridiosoma caaguara sp. nov. do Estado do Rio Grande do Sul, Brasil, é descrita e ilustrada. Baalzebub baubo Coddington, 1986 é registrada pela primeira vez para o Brasil, ampliando-se a distribuição conhecida de Epilineutes globosus (O. P.-Cambridge, 1896), Naatlo splendida (Taczanowski, 1873) e Ogulnius obtectus O. P.-Cambridge, 1882.

Nova espécie de Theridiosoma (Araneae, Theridiosomatidae) do sul do Brasil

Theridiosoma chiripa sp. nov. from the states of Rio Grande do Sul and Santa Catarina, Brazil, is described and illustrated.

Theridiosoma chiripa sp. nov. dos estados do Rio Grande do Sul e Santa Catarina, Brasil, é descrita e ilustrada.

Nova espécie de Theridiosoma (Araneae, Theridiosomatidae) do sul do Brasil

Theridiosoma chiripa sp. nov. from the states of Rio Grande do Sul and Santa Catarina, Brazil, is described and illustrated.

Theridiosoma chiripa sp. nov. dos estados do Rio Grande do Sul e Santa Catarina, Brasil, é descrita e ilustrada.

Aranhas da família Theridiosomatidae: espécie nova e novas ocorrências no Brasil

Theridiosoma caaguara sp. nov. from Rio Grande do Sul state, Brazil, is described and illustrated. Baalzebub baubo Coddington, 1986 is recorded for the first time for Brazil and the known geographic distribution of Epilineutes globosus (O. P.-Cambridge, 1896), Naatlo splendida (Taczanowski, 1873) and Ogulnius obtectus O. P.-Cambridge, 1882 is extended.

Theridiosoma caaguara sp. nov. do Estado do Rio Grande do Sul, Brasil, é descrita e ilustrada. Baalzebub baubo Coddington, 1986 é registrada pela primeira vez para o Brasil, ampliando-se a distribuição conhecida de Epilineutes globosus (O. P.-Cambridge, 1896), Naatlo splendida (Taczanowski, 1873) e Ogulnius obtectus O. P.-Cambridge, 1882.