A number of European species of the genus Arrenurus (Acari, Hydrachnellae) are revised. The following synonyms are established: A. hofsteni Walter and A. sinuator commutatus Viets as junior synonyms of A. latus Barrois & Moniez; A. ornatulus Viets of A. compactus Piersig; A. walteri Koenike of A. neumani Piersig; A. cyanipes (Lucas) sensu Walter and A. bucharicus Sokolow of A. papillator (Müller); A. stjoerdalensis naias Lundblad of A. coronator Thor; A. eugeminus Piersig and A. imitator Koenike of A. geminus George; A. insperatus George of A. stjoerdalensis Thor; Arrenurus brachyurus Viets of A. bifidicodulus Piersig and Arrenurus truncatellus georgei Piersig of A. truncatellus (Müller). A. spatiosus Viets has been raised to species rank, while A. papillator bicolor Viets should stand as a subspecies. A. distans Walter, A. scourfieldi Soar and A. tubulator (Müller) are considered good species. A. bueranus Münchberg, A. curtus George, A. incertus Biesiadka, A. soari George and A. paluster Thor are considered species incertae. A lectotype has been designated for A. scourfieldi. Finally, a small number of old identifications have been re-examined.

Eleven species of the water mite family Torrenticolidae Piersig are reported from interstitial waters of Sicily. The male, female and deutonymph of Torrenticola hyporheica n.sp. are described. The morphological traits of the new species suggest adaptation to life in groundwaters and indicate affinities with other hyporheobiont species of the genus such as T. ramigera Szalay and T. jeanneli Motas & Orghidan. The high number of Torrenticolid-species found in interstitial habitats may be related to the adaptive morphological features of members of this family and more directly to hydrogeological conditions on the island. Torrenticola lativalvata, Torrenticola hyporheica and Torrenticola trinacriae were the most abundant species collected. Marked differences between the distributions of species of the family in Sicily and Corsica are pointed out.

The seasonal and bathymetric occurrence of water mites in the sublittoral and profundal zones of lake Banyoles were studied in 1986-1987. Four species were found in the mud substrate : Neumania deltoides (Piersig, 1894), Neumania imitata Koenike, 1908, Unionicola crassipes (Müller, 1776) and Arrenurus sinuator (Müller, 1776). The maximum depth that water mites reached was 12 m, but they were more frequent and abundant at 5 m depth, mainly in the March-May period (41 individuals per m2). This group represents only 0.08-0.39 % of the total macrobenthic fauna in the sublittoral of lake Banyoles. N. deltoides is the most abundant and widely distributed species. For N. imitata this is the first record in the Iberian peninsula.

Ce travail concerne les données faunistiques et écologiques relatives aux espèces italiennes du genre Torrenticola recueillies dans l'Apennin. Treize espèces ont été signalées, cinq sont nouvelles pour la faune italienne (T. similis, T. lativalvata, T. brevirostris, T. ungeri et T. amplexa). L'étude des caractères dimensionels a permis d'individualiser quelques indices morphologiques de valeur discriminante à un niveau spécifique et a permis de mettre en synonymie quatre espèces. Une distribution différente des espèces entre les secteurs de l'Apennin abruzzin et calabrais a été aussi mise en évidence. L'importance du microhabitat, déterminée par la typologie du cours d'eau, a été soulignée afin d'expliquer la distribution géographique des espèces dans le bassin méditerranéen.