The importance of animals within fluvial geomorphology (zoogeomorphology) is increasingly recognized. Caddisflies (Trichoptera) are a group of aquatic insects known for their bioconstructions. Many caddisfly construct cases from fine sediment and silk. Caddisfly cases differ in size, shape and density from the incorporated sediment and case construction may therefore affect the mobility of these sediments in rivers. However, even though communities of caddisfly often use substantial quantities of sediment in case construction, the effect of these bioconstructions on sediment transport in rivers is unknown. We use a flume experiment to compare the bed shear stress required to transport (1) empty caddisfly cases and (2) individual sediment particles following disaggregation from the case. The cases of three species were considered; two that construct different styles of tubular case (Potamophlax latipennis and Sericostoma personatum) and one that builds a domed case (Agapetus fuscipes). P. latipennis and S. personatum cases were easier to entrain than the sediment grains incorporated into them, whilst A. fuscipes cases were not. Despite their low mass, A. fuscipes cases required the most shear stress to transport them because their domed shape impeded rolling. These findings are important for understanding how caddisfly affect sediment mobility in rivers and how differences in case design reflect case function to the larvae. These results suggest that un-attached tubular caddisfly cases may be preferentially transported over other particles on the river bed and thus caddisfly may increase fluvial entrainment of sand where they occur in high abundance.

• The carnivorous pitcher plant Sarracenia purpurea is native to North America, but has been introduced into Europe, where it is now widespread. We have little understanding of how this species functions in its non-native range. Such understanding will provide insight into S. purpurea ecology and support its use as a model system for investigating food webs. We measured pitcher morphology and prey capture by S. purpurea in Britain and Ireland. • Pitchers were removed from different plants at each of six bogs covering the species rage in the UK and Ireland (n = 10 pitchers per site). For each pitcher we counted and identified every prey item and took measurements of morphology. We also compiled prey capture data for existing studies in Europe and North America. • Prey capture characteristics varied between sites in the UK and Ireland. The amount of prey captured varied 2-fold between sites and was partially explained by differences in pitcher size; larger pitchers caught more prey. The primary prey was Formicidae, Diptera and Coleoptera. At the rank of order, prey composition varied between bogs, some contained mainly Formicidae, some mainly Diptera and some a mix. Plants were more specialised in prey capture at some bogs compared to others. There was no overall difference in prey capture (composition or degree of specialism) at the rank of order between plants in Europe compared to those in North America. At the rank of species, prey capture varied between populations even within the same order. • This study demonstrates a large amount of variability between sites in prey capture characteristics. This may reflect different site characteristics and/or plant strategies, will likely impact plant function, and may impact on the inquiline community. In terms of prey capture at the rank of order S. purpurea functions identically in its non-native range. This supports its use as a natural experiment for understanding food webs