Silvanidae

Abstract: Microbial symbionts of insects provide a range of ecological traits to their hosts that are beneficial in the context of biotic interactions. However, little is known about insect symbiont-mediated adaptation to the abiotic environment, for example, temperature and humidity. Here, we report on an ancient clade of intracellular, bacteriome-located Bacteroidetes symbionts that are associated with grain and wood pest beetles of the phylogenetically distant families Silvanidae and Bostrichidae. In the saw-toothed grain beetle Oryzaephilus surinamensis, we demonstrate that the symbionts affect cuticle thickness, melanization and hydrocarbon profile, enhancing desiccation resistance and thereby strongly improving fitness under dry conditions. Together with earlier observations on symbiont contributions to cuticle biosynthesis in weevils, our findings indicate that convergent acquisitions of bacterial mutualists represented key adaptations enabling diverse pest beetle groups to survive and proliferate under the low ambient humidity that characterizes dry grain storage facilities.

Abstract: Three new African species of Psammoecus Latreille, 1829 are described: Psammoecus nyakabuyensis sp. nov., Psammoecus procerus sp. nov. and Psammoecus sinuaticollis sp. nov. New distribution data and a revised identification key for African Psammoecus are given.

Abstract: The fossil silvanid beetle Mistran ot gen. et sp. nov. is described from Baltic amber. The new taxon is illustrated and compared with morphologically close extant and fossil taxa. A checklist of fossil Silvanidae is provided.

Abstract: Four entomopathogenic nematode species (Steinernema fel-tiae, Steinernema carpocapsae, Heterorhabditis bacteriophora, and Heterorhabditis megidis) were tested in a laboratory bioassay with the aim of studying their efficacy in control of the adults of two stored grain pests, Sitophilus granarius and Oryzaephilus surinamensis. Activity of the biological agents studied was determined at three different concentrations (500, 1000, and 2000 infective juveniles [IJs] per adult) and temperatures (15, 20, and 25°C). The granary weevil mortality rate was higher than the mortality rate of the saw-toothed grain beetle. Heterorhabditis megidis proved to be the least efficient in control of both pests, while no significant differences were recorded between any of the other three nematode species. The experiment demonstrated that the entomopathogenic nematodes were most efficient in the control of S. granarius at 20°C (LC50 after 7-day exposure 803–1195 IJs/adult) and 25°C (LC50 505–1175 IJs/adult). A satisfactory level in control of the pest O. surinamensis was reached at 20°C (LC50 921–1335 IJs/adult). The concentration of the suspension used in our experiment was shown to be a less important factor affecting the biological activity of nematodes against the adults of both stored grain pests. Though the use of entomopathogenic nematodes for control of the tested pests is not possible at the present time, it may be possible to combine this approach with some other (biotechnical) methods in the future.