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Feeding on small tree seeds at fruit falls is a specific adaptation of harpaline ground beetles and their larvae in tropical rain forests. Using mandibles as tools, they have to perforate the seed shell to reach the nutritious interior. The isometric growth of larval mandibles, known from predatory species, would result in a changing ratio between seed and mandible size during the course of development. The stable size of host tree seeds should select an optimum mandible size, similar for the three larval instars in spermophageous species. We found an increasing tendency to maintain the length of the apical mandible part (apex) in seed feeding species.The size increase is higher in the species from Australia, Africa and South East Asia than in the New World species of the genus Notiobia. Feeding experiments have revealed that larvae of species with a stronger increase in apex growth are also able to develop as predators of Drosophila larvae. Our results furthermore point to an influence of beetle size and shell hardness of the host tree seeds on the apex size and its growth rate.

The assessment of the ecological status of aquatic ecosystems for the implementation of the European Water Framework Directive is based on different methods, many of which include the study of macroinvertebrate organisms. We examined whether and how invasive species affect the calculation of metrics used for fresh water assessment utilizing data from different substrate types in the streams of Central Germany. In these streams, the proportion of macroinvertebrate invasives increased from a very low fraction of the community up to 75% of species, or 96% of individuals, within 15 years. The values of the German Saprobic Index (GSI, reflecting the degree of organic load) did not differ significantly between different substrate types or within the examined stream reaches. However, saprobic valences of the species recorded did differ between substrates and between localities. This obvious contradiction is caused by an abundance of exotic species all having a medium GSI index between 2.2 and 2.3. Moreover, the minimum total number of organisms required for this method cannot be reached for a large majority of the sites dominated by invasives making it impossible to use the GSI. Regarding distribution of zonation types, the proportion of metarhithral species is low, and it is even lower on hard substrates than it is on soft substrates. This contradicts the general assumption that dwellers preferring metarhithral reaches (=lower-trout region) will show an affinity for habitats with higher oxygen concentrations and stronger flow velocities, both appearing more on hard than on soft substrates. This latter contradiction results from the classification of the most abundant invasive species Potamopyrgus antipodarum, Dikerogammarus villosus, and Chelicorophium curvispinum in the AQEM taxa reference list. The metrics 'locomotion type' and 'feeding type' were also affected by the presence of invasive species. Possible options for overcoming these assessment problems are discussed.