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The diversity and role of the gut microbiota of insects is a rapidly growing fi eld of entomology, primarily fueled by new metagenomic techniques. Whereas endosymbionts in the guts of xylophagous or herbivorous insects are well studied, the microbiomes in moss-eating (bryophagous) insects remain uncharacterized. Using the Illumina MiSeq platform, we determined the composition of microbiomes in the gut, abdomen and on the body surface of two bryophagous species: Simplocaria semistriata (Fabricius, 1794) and Curimopsis paleata (Erichson, 1846) (Coleoptera: Byrrhidae). Gut microbiomes differed substantially from abdominal microbiomes in the same individuals, which indicates the need to separate them during dissection. Microbiomes in the gut and abdomen differed markedly from surface microbial assemblages. Gut microbiomes in bryophages had the highest MOTU richness, diversity and relative rarity. The eudominant bacteria in the guts and abdomens of bryophages were Novosphingobium, Bradyrhizobium, Ralstonia and Caulobacter, which are responsible for the detoxifi cation of secondary metabolites or nitrogen fi xation. These are less common in the surface samples and, therefore, likely to be associated with the specifi c ability of bryophages to feed on mosses. [ABSTRACT FROM AUTHOR]

Studies of symbioses have traditionally focused on explaining one-to-one interactions between organisms. In reality, symbioses are often much more dynamic. They can involve many interacting members, and change depending on context. In studies of the ambrosia symbiosis--the mutualism between wood borer beetles and fungi--two variables have introduced uncertainty when explaining interactions: imprecise symbiont identification, and disregard for anatomical complexity of the insects. The black twig borer, Xylosandrus compactus Eichhoff, is a globally invasive ambrosia beetle that infests >200 plant species. Despite many studies on this beetle, reports of its primary symbionts are conflicting. We sampled adult X. compactus and infested plant material in central Florida to characterize the fungal symbiont community using dilution series, beetle partitioning, and DNA-based identification. X. compactus was consistently associated with two fungal taxa, Fusarium spp. and Ambrosiella xylebori. Multivariate analyses revealed that A. xylebori was strongly associated with the beetle mycangium while Fusarium spp. were associated with the abdomen and external surfaces. The Fusarium spp. carried by X. compactus are not members of the Ambrosia Fusarium Clade, and are probably not mutualists. Fungal community composition of the mycangium was less variable than external body surfaces, thus providing a more consistent fungal inoculum. This is the first report of spatial partitioning as a mechanism for maintenance of a multimember ambrosia fungus community. Our results provide an explanation for discrepancies among previous reports, and suggest that conflicting results are not due to differences in symbiont communities, but due to inconsistent and incomplete sampling. [ABSTRACT FROM AUTHOR]

Importance: The caterpillar gut is an excellent model system for studying host-microbiome interactions, as it represents an extreme environment for microbial life that usually has low diversity and considerable variability in community composition. Our study design combines feeding caterpillars on a natural and artificial diet with controlled levels of plant secondary metabolites and uses metabarcoding and quantitative PCR to simultaneously profile bacterial and fungal assemblages, which has never been performed. Moreover, we focus on multiple caterpillar species and consider diet breadth. Contrary to many previous studies, our study suggested the functional importance of certain microbial taxa, especially bacteria, and confirmed the previously proposed lower importance of fungi for caterpillar holobiont. Our study revealed the lack of differences between monophagous and polyphagous species in the responses of microbial assemblages to plant secondary metabolites, suggesting the limited role of the microbiome in the plasticity of the herbivore diet., Competing Interests: The authors declare no conflict of interest.

Importance: Ambrosia gall midges are endophagous insect herbivores whose larvae live enclosed within a single gall for their entire development period. They may exhibit phytomycetophagy, a remarkable feeding mode that involves the consumption of plant biomass and mycelia of their cultivated gall symbionts. Thus, AGMs are ideal model organisms for studying the role of microorganisms in the evolution of host specificity in insects. However, compared to other fungus-farming insects, insect-fungus mutualism in AGMs has been neglected. Our study is the first to use DNA metabarcoding to characterize the complete mycobiome of the entire system of the gall-forming insects as we profiled gall surfaces, nutritive mycelia, and larvae. Interestingly, larval mycobiomes were significantly different from their nutritive mycelia, although Botryosphaeria dothidea dominated the nutritive mycelia, regardless of the evolutionary separation of the tribes studied. Therefore, we confirmed a long-time hypothesized paradigm for the important evolutionary association of this fungus with AGMs., Competing Interests: The authors declare no conflict of interest.

The phenomenon of hydrophobicity of insect cuticles has received great attention from technical fields due to its wide applicability to industry or medicine. However, in an ecological/evolutionary context such studies remain scarce. We measured spatial differences in wing wettability in Lestes sponsa (Odonata: Lestidae), a damselfly species that can submerge during oviposition, and discussed the possible functional significance. Using dynamic contact angle (CA) measurements together with scanning electron microscopy (SEM), we investigated differences in wettability among distal, middle and proximal wing regions, and in surface nanostructures potentially responsible for observed differences. As we moved from distal towards more proximal parts, mean values of advancing and receding CAs gradually increased from 104° to 149°, and from 67° to 123°, respectively, indicating that wing tips were significantly less hydrophobic than more proximal parts. Moreover, values of CA hysteresis for the respective wing parts decreased from 38° to 26°, suggesting greater instability of the structure of the wing tips. Accordingly, compared with more proximal parts, SEM revealed higher damage of the wax nanostructures at the distal region. The observed wettability gradient is well explained by the submergence behaviour of L. sponsa during underwater oviposition. Our study thus proposed the existence of species-dependent hydrophobicity gradient on odonate wings caused by different ovipositional strategies., Competing Interests: We declare we have no competing interests, (© 2020 The Authors.)