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This work provides the results of a survey of entomonematodes parasites of grasshoppers in grasslands of the Pampean Region, Argentina. Camino and Stock, 1989. The values of parasitism ranged between 1-12%, and intensity not overcome the number of 5.0 nematodes per larva. The nematodes observed showed specificity, not registering the same species of parasite in more than one host species. The Pampean region constituted an area with high diversity of mermithids where new species could be consider as bioregulator agents of this troublesome insect pests in agricultural areas of Argentina.Keywords: nematodes, Acrididae, pest, agriculture, Argentina. Nematóides (Mermithidae) parasitando gafanhotos (Orthoptera: Acrididae) nos Pampas região, a Argentina ResumoEste trabalho apresenta os resultados de uma pesquisa entomonematode parasitando gafanhotos em pastagens da região pampeana, Argentina. Ninfas de Staurorhectus longicornis Giglio-Tos, Laplatacris dispar Rhen de 1939, Dichroplus elongatus Giglio-Tos, 1894 e Metaleptea brevicornis (L.) (Orthoptera: Acrididae) foram coletados. Mermithidae era a única família registrado com sete espécies: Agamermis decaudata Cobb, Steiner and Christie, 1923, Amphimermis bonaerensis Miralles and Camino, 1983, Amphimermis dichroplusi Camino and Lange, 1997, Amphimermis ronderosi Camino and Lange, 1997, Hexamermis coclhearius Stock and Camino, 1992, Hexamermis ovistriata Stock and Camino, 1992, e Longimermis acridophila Camino and imagem, de 1989. Os valores de parasitismo variou entre 1-12%, e intensidade não superar o número de 5,0 nematóides por larva. Os nemátodos observados demonstraram especificidade, não registar as mesmas espécies de parasita em mais do que uma espécie de hospedeiro. A região pampeana constituída uma área com alta diversidade de mermithids onde novas espécies poderiam ser consideradas como agentes bio-reguladores deste incômodos insetos pragas em áreas agrícolas da Argentina.

Population dynamics of the immature stages of Aedes aegypti (Diptera: Culicidae), vector of dengue: a longitudinal study (1996-2000). A four year study was conducted on a natural population of immature stages of Aedes aegypti after the re-invasion of Argentina by this vector in 1987. Thirty six plastic containers with 700 ml of dechlorinated water were placed in the La Plata Zoological Garden, La Plata, Argentina. A strip of filter paper around each container was added to facilitate egg counting. Eggs, larvae and pupae were counted weekly in each container from September, 1996 to August, 2000. After egg counting, papers were submerged to facilitate egg hatching and a new paper was placed in each container. Presence of A. aegypti immature stages was recorded from December-January to June during each of the four years of this study.

Fourteen species of mosquito and several species of non-target aquatic organisms were tested for susceptibility to the neotropical mermithid nematode, Strelkovimermis spiculatus. All species of Aedes, Anopheles, Culex, Isostomyia and Ochlerotatus, plus one of the two Psorophora species exposed to S. spiculatus preparasites, were parasitised. None of the non-target aquatic organisms exposed to S. spiculatus were infected, with the exception of Chironomidae larvae in which nematode penetration was observed although host reaction in the form of nematode melanisation occurred 24-48 h post-infection, the nematodes dying within the host.