The present study aimed to determine the selectivity of the pyrethroid lambdacyhalothrin on arthropod natural enemy populations in irrigated rice fields in Rio Grande do Sul, Brazil. The study was conducted at three sites: districts of Cachoeira do Sul, Eldorado do Sul and Capivari do Sul during the crop years of 2007/2008 and 2008/2009. Each site consisted of two subareas divided into four plots. One of the subareas received a spray application of 150 ml/ha of lambdacyhalothrin CS 50, while the other subarea was untreated. Arthropods were collected at 2, 15, 30 and 45 days after the application of the insecticide to assess its impact on natural enemy populations. The results indicated consistent differences in natural enemy populations between the treated and untreated areas, especially within the first 2 weeks after the application of the insecticide. Principal components analysis together with χ2 analysis revealed differences in the populations of Tetragnathidae, Anyphaenidae, Araneidae, Coccinellidae, Phytoseiidae and Coenagrionidae between the treated and untreated areas. This study indicated the existence of a great diversity of arthropod natural enemies in irrigated rice fields in a subtropical environment similar to that reported previously from rice fields in tropical environments. In addition, lambdacyhalothrin was shown to be a rapid acting insecticide, with a significant initial decrease in natural enemy populations followed by a rapid recovery beginning at 2 weeks after the application of the insecticide. Especially disconcerting is the severe impact of the insecticide on Phytoseiidae and Araneidae, which are considered key natural enemies for the management of rice pests in southern Brazil.

Madagascar has one of the world's highest rates of human population increase, which is coupled with an increase of resource exploitation, particularly food and firewood. Forests are cleared and converted to rice fields or plantations (mainly Eucalyptus or pine). How does deforestation affect the amphibian diversity of the original biotope, the rain forest? To answer this question, the amphibian fauna of intact rain forests was compared with that of secondary forests, Eucalyptus plantations and rice fields. The main consequence of rain forest disturbance was loss of amphibian species. Compared with an intact forest, species richness in secondary forests, Eucalyptus plantations and rice fields were 54%, 46% and 12%, respectively. Species number and individual density increased with increasing structural complexity of the habitat and the presence of water bodies. The reproductive strategy of the species could be decisive for the presence or absence of single species in different habitats. With increasing degradation the percentage of species spawning in water increased. Correspondingly, Hyperoliidae and Raninae were characteristic of degraded habitats, whereas Microhylidae and Mantellinae were representative of natural habitats.

A new corer is described which may be used in sediments of shallow standing waters, such as in rice fields, and which facilitatesthe study of the vertical distribution of the invertebrate fauna at 2 cm depth intervals. Its small surface area permits quantitativesampling of the sediment-dwelling fauna, particularly the chironomid larvae, around the roots of rice-plants. Results arepresented and the efficiency of the sampling method is discussed.