Insects

Longhorn beetles mainly harm trees, flowers, and certain crops. They are closely associated with their host plants and often climb on vertical trunks, branches, and the underside of leaves. Their tarsi have numerous micro-scale adhesive setae on the ventral side. These setae provide sufficient force to enable the beetles to adhere firmly to smooth or slightly micro-structured surfaces. This study observed and analyzed the ultrastructures of the adhesive setae of three species from different subfamilies of Cerambycidae and one species from Vesperidae using a scanning electron microscope. The comparative analysis focused on characterizing the types, morphology, distribution patterns and adhesion mechanisms of the adhesive ultrastructures in four longhorn beetle species. The results showed that the longhorn beetles generally had pseudotetramerous tarsi (except An. chinensis, which had tetramerous tarsi), and that tarsomeres I–III were expanded and widened to increase the contact area between the tarsi and the substrate. Furthermore, a large number of micro-scale adhesive setae were present on the ventral surface of these tarsomeres. In total, five types of adhesive setae were found in the four species studied. The three species belonging to the Cerambycidae family exhibited adhesive setae with numerous short setules, while in the species Mantitheus pekinensis belonging to Vesperidae, there are two types of adhesive setae without any short setules. The differentiation of the adhesive structures in longhorn beetles is shaped by the combined effects of phylogeny, sexual dimorphism, and host-plant adaptations.

Here, we report on the complexity of the taxonomy and species evolution within the monophyletic genus Rhamphus, which includes some of the smallest members of the Curculionidae family and whose species are morphologically almost indistinguishable from each other. Despite their similar appearance, we found high divergence and varying evolutionary rates among observed species groups living both in sympatry and allopatry in the western Palearctic. On the basis of subtle morphological differences and molecular evidence, we defined eight morphotypic groups and 14 species, of which 6 are newly described in this paper: R. diottii sp. nov. and R. ibericus sp. nov. (monzinii-group), R. cypricus sp. nov. and R. macedonicus sp. nov. (cypricus-group), R. betulae sp. nov. and R. crypticus sp. nov. (pulicarius group). Rhamphus morphotypic groups showed intense species radiation and cryptic speciation, with an estimated genetic divergence of 4.2–18.8% (uncorrected) in the barcoding region of the mitochondrial COI gene. The estimated divergence of the two nuclear markers, nEF-1α and nCAD, ranged from 1 to 11.9% and 0.5 to 15%, respectively. Phylogenetic analyses using both single and partitioned multigene adequately resolved the relationships between Rhamphus species and identified all groups and the species with high nodal support. According to our study, Rhamphus species cluster into monophyletic groups that are partly defined by their host plant associations and by subtle differences in penis shape. No substantial differences in female genitalia were found. Most of the species exhibit relatively rapid species radiation, which is cryptic by nature.

The two-spotted spider mite, Tetranychus urticae, is a global pest with increasing resistance to conventional acaricides, prompting the search for sustainable alternatives. Essential oils (EOs) are promising botanical biocides due to ecological safety and multitarget action. We evaluated lethal and sublethal effects of EOs from Alpinia zerumbet and Mesosphaerum suaveolens against T. urticae. Oils were obtained by hydrodistillation and characterized by GC–MS (major constituents: A. zerumbet—1,8-cineole 14.05%, sabinene 12.6%; M. suaveolens—β-sabinene (predominant), spathulenol 12.28%, 1,8-cineole 11.01%). In adult bioassays, M. suaveolens was more toxic (LC₅₀ = 4.24 µL mL⁻¹), whereas A. zerumbet showed LC₅₀ = 8.74 and LC₉₀ = 46.24 µL mL⁻¹. In ovicidal assays at LC₉₀, egg viability declined to 2% with A. zerumbet versus 57% with M. suaveolens. Repellency at sublethal concentrations (LC₂₀–LC₃₀) was high for both oils (≥75%) and exceeded 90% for M. suaveolens. Both oils suppressed population growth (instantaneous rate r_i reduced from 0.5848 in the control to 0.4746–0.5155 under treatments). PCA confirmed lethal concentration and repellency as the main discriminators among treatments. These data demonstrate the multitarget potential of A. zerumbet and M. suaveolens EOs as botanical acaricides for sustainable management of T. urticae.