ABSTRACT Many studies have revealed that water mite communities can be affected by the physical and chemical parameters of the water. The similarity between the water ‘mite assemblages in local water bodies and in irrigated rice areas can be a way to measure the water conditions, enabling an assessment of the anthropic impact in the environment. The aim of this study was to evaluate the distribution of water mites in lakes and irrigated rice fields in south Brazil. To accomplish that we characterized the distinctive environments using physical and chemical variables such as pH, turbidity (NTU), water temperature (°C) and dissolved oxygen (mg/L), in order to verify the influence of these abiotic factors on the species composition of water mite communities; and to compare water mite abundance, richness and composition among different habitats. We assessed three native lakes and four sites with irrigated rice cultivation. Our results showed, for the first time in Brazil, strong correlations between the water mite fauna and turbidity. In addition, native lakes were richer and had greater mite abundance when compared with the irrigated rice areas.

ABSTRACT Two new species of Tydeidae are described, Brachytydeus lorenzatus sp. nov. and Quasitydeus feresi sp. nov. Brachytydeus lorenzatus sp. nov. differs from B. aegyptiaca (Rasmy & El Bagoury, 1979) by having a reticulated area on the region of f1 and f2 , dorsal setae smooth, solenidion (I shorter than or equal to the width of tarsus I, most setae on dorsal shield shorter than the length between their bases and setae d forked distally. The new species is distinguished from B. scutatus Silva, Rocha & Ferla, 2013 by having a slightly reticulate area on the aspidosoma, near setae bo , all dorsal setae slender and club-shaped. Quasitydeus feresi sp. nov. differs from the only other species of the genus, Q. ricensis (Baker, 1970), by having all dorsal setae simple and serrated, similar in shape. Eleven tydeoid species are reported also from several plants native to the state of Rio Grande do Sul, Brazil. This is the second species of Brachytydeus Thor, 1931 described from and the second species described for Quasitydeus Kaźmierski, 1996.

A survey of predaceous mites in apple (Prunus malus L.) orchards in central part of Rio Grande do Sul state (Serio and Capitão counties) was conducted from September 1993 to May 1994. The majority of the predators collected belonged to the Phytoseiidae family. The most common species were Neoseiulus tunus (DeLeon), Euseius alatus DeLeon, and Euseius brazilli (El-Benhawy). In Capitão, Euseius spp. were the predominant phytoseiids from the beginning of December 1993 to mid March 1994. In Serio, Euseius spp. were more abundant than N. tunus only at the end of January. The number of phytoseiids increased from the end of December 1993 to mid February 1994. The highest levels of Stigmaeidae and Cunaxidae occurred from the end of February to mid May, after the reduction of phytoseiids.