The three larval instars of Gymnochthebius jensenhaarupi (Knisch, 1924) are described and illustrated, including a detailed analysis of their chaetotaxy and porotaxy. The specimens used in this study were collected with adults of G. jensenhaarupi and have been identified as such by association. Comparative notes on the morphology of these larvae with other species of the subfamily Ochthebiinae are given. A hypothesis of phylogenetic relationships between G. jensenhaarupi and other members of Ochthebiinae with thoroughly described larvae is presented. The monophyly of Ochthebiinae is supported by additional larval features. On the other hand Ochthebius, as currently composed, seems to by paraphyletic. Gymnochthebius Orchymont, 1943 is confirmed as the sister group of Aulacochthebius Kuwert, 1887.
The Hydraenidae and Elmidae assemblages living in the Órbigo River Basin (NW Spain) were studied during one year. The aim of the research was to determine which factors were best related to species composition. This knowledge is the first step towards the definition of indicator species or assemblages.
Canonical Correspondence Analysis (CCA) showed that altitudinal gradient was the factor most correlated with beetle distribution. However, some other variables, such as water mineralization and eutrophication, were also important.
Using TWINSPAN program, groups of sites were defined and, afterwards, represented on the CCA diagram. Several species assemblages were defined on the basis of their frequencies of occurrence in these site groups. The environmental features of site groups and beetle assemblages were assessed with the aid of CCA. In this way, assemblages typical of high reaches could be separated from those of low stretches of the rivers. Similarly, communities from non-polluted waters could also be defined. Although several species are present in polluted sites, no assemblage exclusive to these sites has been found.
Aulacochthebius libertarius sp. n. is described from the Moroccan Anti Atlas. The aedeagus of A. exaratus (Mulsant) and A. narentinus (Reitter), the two other known Palaearctic species of the genus, are figured, and their similarities discussed. The Palaearctic species of Aulacochthebius do not seem to form a natural group, A. narentinus and A. libertarius sp. n. being more similar to some Ethiopian and Oriental species.