A new species of Toxorhinus Lacordaire (Coleoptera: Curculionidae: Dryophthorinae; Rhynchophorini) from Ecuador.

Toxorhinus amarillo Anderson, new species (Coleoptera: Curculionidae: Dryophthorinae; Rhynchophorini), is here described from Ecuador (Cotopaxi, Biochoa Otonga). The species is compared to the other two species in the genus.

The morphological allometry of four closely related and coexisting insect species reveals adaptation to the mean and variability of the resource size.

The size of organisms may result from various, sometimes antagonistic forces operating on distinct traits, within an evolutionary framework that may also be constraining. Morphological allometry, referring to the way trait size scales with body size, has been shown to reflect ecological adaptation to the mean size of the resource exploited. We examined the allometric relationships between rostrum and body size among four insect (Curculio spp.) specialists of oak acorns. In all four species, weevil females drill a hole with their rostrum prior depositing one or a few eggs inside the seed. The four weevil species, that coexist on the same individual trees, displayed partitioned egg-laying periods in the year, thereby encountering acorns of different size and maturation stage. We found marked differences in the allometric slope among females: species laying eggs late in the season had a steeper slope, leading to increasingly longer rostrum relative to body length, along with the mean size of the growing acorns. Females of the smallest species had the longest oviposition period and also had the steepest slope, which provided them with the most variable rostrum length, thereby matching the variable size of the resource through time. Our work highlights the need to consider not only the average size but also the degree of variability in resource size to understand the adaptive value of allometric relationships.

Functional characteristics of the rigid elytra in a bamboo weevil beetle Cyrtotrachelus buqueti.

The bamboo weevil beetle, Cyrtotrachelus buqueti, has evolved a particular flight pattern. When crawling, the beetle folds the flexible hind wings and stuffs under the rigid elytra. During flight, the hind wings are deployed through a series of deployment joints that are passively driven by flapping forces. When the hind wings are fully expanded, the unfolding joint realises self-locking. At this time, the hind wings act as a folded wing membrane and flap simultaneously with the elytra to generate aerodynamics. The functional characteristics of the elytra of the bamboo weevil beetle were investigated, including microscopic morphology, kinematic properties and aerodynamic forces of the elytra. In particular, the flapping kinematics of the elytra were measured using high-speed cameras and reconstructed using a modified direct linear transformation algorithm. Although the elytra are passively flapped by the flapping of the hind wings, the analysis shows that its flapping wing trajectory is a double figure-eight pattern with flapping amplitude and angle of attack. The results show that the passive flapping of elytra produces aerodynamic forces that cannot be ignored. The kinematics of the elytra suggest that this beetle may use well-known flapping mechanisms such as a delayed stall and clap and fling.

Two new species of Metapocyrtus (Metapocyrtus) Heller 1912 from Mindanao, Philippines (Curculionidae, Entiminae, Pachyrhynchini).

Two new species of Curculionidae, Pachyrhynchini, Metapocyrtus waoensis sp. nov., and M. lanaoensis sp. nov., both from western Mindanao are described. Images of habitus and fully everted endophallus and illustrations of male genitalia are provided for each species.

Growth temperature effect on mandibles' ontogeny and sexual dimorphism in the ambrosia beetle Xyleborus affinis (Curculionidae: Scolytinae).

Ambrosia beetles from the genus Xyleborus are important vectors of fungal pathogens in forest and agricultural systems, yet the influence of temperature on their morphological development has been poorly studied. Because host colonization and ambrosial fungi cultivation is mostly restricted to females, it is possible to speculate on strong sexual dimorphism expression in secondary sexual characters and ecological segregation between sexes. Here, we determined the effect of different growing temperatures (17, 23, 26 and 29 °C) on mandible ontogeny of larvae and adult individuals of X. affinis, and sexual dimorphism in adults, in shape and size variation using geometric morphometrics. Mandible shape change showed significant differences in magnitude and direction through larval ontogeny among temperature treatments. Sexual shape and size dimorphism were found in adult mandibles, and the degree of sexual dimorphism was dependent on growth temperature, with a significant effect of the interaction between temperature and sex on mandible shape and size variation. Higher morphological differences were observed at the base of mandibles among temperature treatments in adults and a gradual narrowing trend with temperature increments. These findings could have consequences on feeding performance and fungus cultivation inside colonies, potentially influencing their ability to establish populations in new geographical areas.

Transmission of Metarhizium anisopliae and Beauveria bassiana to adults of Kuschelorhynchus macadamiae (Coleoptera: Curculionidae) from infected adults and conidiated cadavers.

Kuschelorhynchus macadamiae is a major pest of macadamias in Australia, causing yield losses of up to 15%. Our previous studies have shown the weevil is susceptible to Beauveria bassiana and Metarhizium anisopliae. The aim of this study was to investigate horizontal transmission of both fungal species to healthy weevils from both infected adults and weevil cadavers. In a confined environment the mortality of healthy adults caused by the transmission of conidia from live fungus-infected adults was < 50%. Under similar experimental conditions, the mortality of healthy adults reached 100% when exposed to conidiated cadavers. However, when conidiated cadavers were used in more spacious environments (insect cages), the mortality of adults was < 80%. Using scanning electron microscopy, it was observed that all healthy adults had conidia attached to all external parts of the body. This suggests that although the conidia were readily transferred to the adults, the lower mortality in the larger insect cages could be the result of an unfavourable environmental factor such as low humidity. The presence of conidia attached to all the adults indicated that they did not show any discriminatory behaviour such as avoidance of conidiated cadavers infected by these two fungal species. The results from this study show that there is potential for enhanced control of adult K. macadamiae via transmission from either fungus-infected adults or conidiated cadavers and this could strengthen sustainable pest management in macadamias.

Morphological response of the red palm weevil, Rhynchophorus ferrugineus, to a transient low temperature analyzed by computer tomography and holographic microscopy.

The red palm weevil (RPW), Rhynchophorus ferrugineus, is one of the worst palm pests worldwide. Our study aims to assess its internal and external morphological response to a sudden but transient decrease in the environmental temperature. Wild pre-pupae were subjected for 7 days to either low (5.0 ± 0.5 °C) or ambient temperature (23 ± 1 °C). Such conditions mimic a thermal anomaly happening in the larval stage most exposed to environmental factors. We quantified the changes undergone at: 1) the internal morphology, by X-Ray Computer Tomography (CT); 2) the 3-D integument' architecture, by Digital Holographic Microscopy (DHM); and 3) the glucose in hemolymph as a potential endogenous cryoprotectant. From X-ray CT we found that both pre-pupae subjected to cold and those remaining at ambient temperature follow a development where their fat body content decreases while a thick and dense cuticle is formed. There was no difference between both groups in the rate of change of fat body/dense tissues. Nevertheless, the cold group presents a slight developmental delay at the level of hemolymph content. Through DHM we again obtained that pre-pupae subjected to cold have not experienced a stop in their development. However, a more obvious developmental delay is now observed in this group at the level of the integumental roughness. Finally, regarding glucose, we found similar levels in control and ambient temperature larvae, while it was clearly increased in 51,7% of those subjected to cold. Our whole results provide morphological and biochemical evidence showing that the larval-pupal transition of the RPW continues almost undisturbed even during the quiescent state induced by a sudden and severe cold event. Nevertheless, a certain developmental delay is observed in both internal and external morphology. Additionally, the increased glucose level only found in the cold group suggests that glucose is part of the RPW cold tolerance strategy.

Sexual Dimorphism in Anthonomus santacruzi (Coleoptera: Curculionidae): a Biological Control Agent of Solanum mauritianum Scopoli (Solanaceae).

There is evident variation in body size amongst Anthonomus santacruzi Hustache, 1924, weevils. The aims of this study were to assess if the variation in body size in A. santacruzi weevils is a result of sexual dimorphism and what features can be used to distinguish males from females. The weevils were collected from field sites in Mpumalanga, South Africa, where they were introduced as biocontrol agents of Solanum mauritianum Scopoli. Body structures and the presence/absence of the tergal notch was examined under an optical stereomicroscope and SEM to assess differences between sexes. The morphometric analysis of the body structures included rostrum length (base-apex and antennal insertion-apex), elytral length and width, pronotum length and width, first tarsus length, first tibia length, funiculus length and total body length. Rostrum length, elytra length and width and total body length were significantly larger in females than in males. A tergal notch in the 8th abdominal tergite was present in males and absent in females. The body structure; of rostrum length, elytra length and width and total body length overlapped between sexes in some specimens. The abdominal tergal notch was found to be the most useful body structure to distinguish males from females in A. santacruzi.

Anatomical and histological studies of the alimentary canal of adult maize leaf weevil, Tanymecusdilaticollis Gyllenhal, 1834 (Coleoptera: Curculionidae).

In this study, ananatomical and histological study was conducted on the alimentary canal of Tanymecusdilaticollis (Coleoptera: Curculionidae), which is an economic polyphagous pest species, to study the relationship between the structure of the alimentary canal and the feeding habit. Therefore, the structure of the alimentary canal of T. dilaticollis was examined using light and electron microscopies. Results have shown that the alimentary canal in T. dilaticollis is consisted of three separate regions as foregut, midgut, and hindgut structurally between the mouth and the anus, which pass from head, thorax, and abdomen. The foregut consists of pharynx, esophagus, crop and proventriculus and in the crop part, expansion is seen compared to other foregut parts. Midgut of T. dilaticollis is the largest part of digestion system. The anterior region of midgut is twofolds wider than the posterior region. The posterior midgut extends tubularly and it is connected to eightgastric caeca. The hindgut of T. dilaticollis consists of fourparts as pylorus, ileum, colon, and rectum. Well-developed muscle layers are found near the rectum and genital chamber. These results contribute to further studies on the ecology and biological control agents of Coleoptera and to provide a broad comparison of alimentary canal of Coleoptera species.

Wing-kinematics measurement and flight modelling of the bamboo weevil C. buqueti.

Insects are one of the most agile flyers in nature, and studying the kinematics of their wings can provide important data for the design of insect-like wing-flapping micro aerial vehicles. This study integrates high-speed photogrammetry and three-dimensional (3D) force measurement system to explore the kinematics of Cyrtotrachelus buqueti during the wing-flapping flight. The tracking point at the wing tip of the hind wing was recorded using high-speed videography. The lift-thrust force characteristic of wing-flapping motion was obtained by the 3D force sensor. Quantitative measurements of wing kinematics show that the wing-flapping pattern of the hind wing of C. buqueti was revealed as a double figure-eight trajectory. The kinematic modelling of the wing-flapping pattern was then established by converting the flapping motion into rotational motion about the pivoting wing base in the reference coordinate system. Moreover, the lift force generated by C. buqueti during the wing-flapping flight is sufficient to support its body weight without the need to use thrust force to compensate for the lack of lift force.

Revealing the respiratory system of the coffee berry borer (Hypothenemus hampei; Coleoptera: Curculionidae: Scolytinae) using micro-computed tomography.

The coffee berry borer (Hypothenemus hampei) is the most economically important insect pest of coffee globally. Micro-computed tomography (micro-CT) was used to reconstruct the respiratory system of this species for the first time; this is the smallest insect (ca. 2 mm long) for which this has been done to date. Anatomical details of the spiracles and tracheal tubes are described, images presented, and new terms introduced. The total volume and the relationship between tracheal lumen diameter, length and volume are also presented. The total length of the tracheal tubes are seventy times the length of the entire animal. Videos and a 3D model for use with mobile devices are included as supplementary information; these could be useful for future research and for teaching insect anatomy to students and the public in general.

Structural characteristics analysis of the hind wings in a bamboo weevil (Cyrtotrachelus buqueti).

The finite element method is a powerful tool for evaluating the experimental results. It can help to study the flight mechanism of insects and the structural characteristics of flying wings. Therefore, the research object based on the hind wings of Cyrtotrachelus buqueti (C. buqueti) was completed here. A finite element model with a length of 45 mm in the spanwise direction and a 16 mm width in the chordwise direction were established. We used a three-dimensional (3D) scanner to scan a real hind wing to obtain point cloud images. The physical model of the hind wing was carried out by using both the software Imageware and Unigraphics NX. To quantify the quality of the finite element model of the hind wing, the material properties of the wing membranes and veins were conducted by the tensile testing machine. The structural static properties of the hind wing, including static characteristics analysis and natural vibration modal analysis, were analysed by ANSYS; the stress and deflection under uniformly distributed load, bending moment, and torque were, respectively, shown. It was found that the model only had a small deformation, which shows that the hind wings of C. buqueti have excellent structural properties.

Avoidance of Catastrophic Structural Failure as an Evolutionary Constraint: Biomechanics of the Acorn Weevil Rostrum.

The acorn weevil (Curculio Linnaeus, 1758) rostrum (snout) exhibits remarkable flexibility and toughness derived from the microarchitecture of its exoskeleton. Modifications to the composite profile of the rostral cuticle that simultaneously enhance the flexibility and toughness of the distal portion of the snout are characterized. Using classical laminate plate theory, the effect of these modifications on the elastic behavior of the exoskeleton is estimated. It is shown that the tensile behavior of the rostrum across six Curculio species with high morphological variation correlates with changes in the relative layer thicknesses and orientation angles of layers in the exoskeleton. Accordingly, increased endocuticle thickness is strongly correlated with increased tensile strength. Rostrum stiffness is shown to be inversely correlated with work of fracture; thus allowing a highly curved rostrum to completely straighten without structural damage. Finally, exocuticle rich invaginations of the occipital sutures are identified both as a likely site of crack initiation in tensile failure and as a source of morphological constraint on the evolution of the rostrum in Curculio weevils. It is concluded that avoidance of catastrophic structural failure, as initiated in these sutures under tension, is the driving selective pressure in the evolution of the female Curculio rostrum.

The histomorphological structure of the male reproductive system of maize leaf weevil Tanymecus dilaticollis Gyllenhal, 1834 (Coleoptera: Curculionidae).

The histomorphology of the reproductive system and the germ cells has been useful to establish phylogenetic relationships in many insects. However, these elements remain little known in the Curculionidae. In this study, histomorphological structure of the male reproductive system of Tanymecus dilaticollis, which is economically important, is described, illustrated using stereomicroscopy, light microscopy, and scanning electron microscopy techniques, and discussed in relation to other Coleoptera species. Results showed that distinctive features of the male reproductive system of T. dilaticollis consist of a pair of yellowish testes, a pair of seminal vesicles, a pair of vasa deferentia, an ejaculatory duct, accessory glands, prostate glands, and aedeagus. Each testis is subdivided into two testicular follicles, enclosed by a peritoneal sheath. Each follicle of the mature testes is full sperm cysts with germ cells at various stages development of spermatogenesis. The testes have four types of germ cells (spermatogonia, spermatocytes, spermatids, and spermatozoa). They are occupied by the growth zone containing spermatogonia and spermatocytes, the maturation zone containing spermatids, while differentiation zone containing spermatozoa. There is a seminal vesicle at the center of each testis. Most mature sperms are stored in the seminal vesicle. Each testis is attached to the vas deferens by a stalk-like seminal vesicle. In the distal part, vasa deferentia fuse with the ejaculatory duct. It is linked to the aedeagus. The provided results will contribute to the understanding of the reproductive cell biology of Curculionidae.

Microstructure and material properties of hind wings of a bamboo weevil Cyrtotrachelus buqueti (Coleoptera: Curculionidae).

Wings of flying insects, as representative biomaterials, are composed of a flexible membrane and a stiff vein structure that are prone to bending and deformation under aerodynamic forces. Therefore, we must investigate the application value of insect wings in the field of engineering design from the perspective of bionics, which is a new challenge. In this study, we measured the mechanical properties of the hind wings of Cyrtotrachelus buqueti including "dried" and "fresh" samples. The wing membrane samples were prepared by carefully cutting the hind wings into 2.0 mm by 8.0 mm rectangular segments using a gauge. As the major wing veins are the main loading units under aerodynamic forces, we also separated them from the wings as a kind of investigative specimen. The wing membranes were adhered to a specially designed paper fixture and the mechanical properties of the wing veins and membranes were evaluated using a tensile testing machine. We observed the microstructure of the samples using a scanning electron microscope and accurately measured the thicknesses of desired the wing membranes and veins. The results show that there is a difference in the mechanical properties of the two samples. The elastic modulus and Poisson's ratios vary over the region in hind wing, so we can conclude that the wing membrane is an anisotropic and non-uniform material.

Nanoindentation Properties and Finite Element Analysis of the Rostrum of Cyrtotrachelus buqueti Guer (Coleoptera: Curculionidae).

This work focuses on the application of nanoindentation measurements and the finite element method for analyzing the mechanical properties of the rostrum of the outstanding driller Cyrtotrachelus buqueti Guer. Nanoindentation tests were carried out to measure the Young's modulus and hardness of the rostrum, with the results for the "dry" samples being 13.886 ± 0.75 and 0.368 ± 0.0445 GPa, respectively. The values for the "fresh" samples showed no clear difference from those of the "dry" ones. Moreover, field observation was conducted to determine the motion behaviors of the rostrum on the weevil. Micro-computed tomography technology was employed to obtain structural information about the rostrum, using 9 µm slices. A real three-dimensional model of the rostrum was created using the MIMICS application. Finally, the mechanical properties of the rostrum were determined by finite element analysis. It was concluded that the rostrum provides an ideal biological template for the design of biocomposite materials and lightweight tube-shaped structures. The properties determined in this study can potentially be applied in different fields, such as in the design of automotive hybrid transmission shafts, helicopter tail drive shafts, robotic arms, and other sandwich structures in aerospace engineering.

An Assessment of Old and New Characters Using Traditional and Geometric Morphometrics for the Identification of Dendroctonus approximatus and Dendroctonus parallelocollis (Curculionidae: Scolytinae).

There have been numerous changes in the nomenclature of species of Dendroctonus. The case of Dendroctonus parallelocollis Chapuis and Dendroctonus approximatus Dietz has been particularly noteworthy. These bark beetles colonize pine trees but are not aggressive species. The high morphological similarity, their overlapping geographical distribution, and the limited knowledge of these species have resulted in taxonomic confusion. The aim of the present study was to assess morphological characters reported in the literature and to scrutinize new characters that might be useful for the separation of these species. We evaluated 26 morphological attributes and performed geometric morphometrics analysis of the antenna, pronotum, spermatheca, and seminal rod to test if the variations in the shape of these structures allow the recognition of additional discrete characters to differentiate them. Our results show that five double-state characters of external morphology are useful to identify these species, and the shape of antenna, spermatheca, and seminal rod.

Bark beetles use a spring-loaded mechanism to produce variable song patterns.

Many insects vary their song patterns to communicate different messages, but the underlying biomechanisms are often poorly understood. Here, we report on the mechanics of sound production and variation in an elytro-tergal stridulator, male Dendroctonus valens bark beetles. Using ablation experiments coupled with high-speed video and audio recordings, we show that: (1) chirps are produced using a stridulatory file on the left elytron (forewing) and a protrusion (plectrum) on the seventh abdominal segment; (2) chirps are produced by 'spring stridulation', a catch-and-release mechanism whereby the plectrum catches on a file tooth and, upon release, springs forward along the file; and (3) variability in chirp types is caused by introducing multiple catch-and-release events along the file to create regular interruptions. These results provide experimental evidence for the mechanics of elytro-tergal stridulation, and provide insight into how an insect can incorporate variability into its acoustic repertoire using a spring-loaded mechanism.

Plasticity of mycangia in Xylosandrus ambrosia beetles.

Insects that depend on microbial mutualists evolved a variety of organs to transport the microsymbionts while dispersing. The ontogeny and variability of such organs is rarely studied, and the microsymbiont's effects on the animal tissue development remain unknown in most cases. Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae or Platypodinae) and their mutualistic fungi are an ideal system to study the animal-fungus interactions. While the interspecific diversity of their fungus transport organ-mycangia-is well-known, their developmental plasticity has been poorly described. To determine the ontogeny of the mycangium and the influence of the symbiotic fungus on the tissue development, we dissected by hand or scanned with micro-CT the mycangia in various developmental stages in five Xylosandrus ambrosia beetle species that possess a large, mesonotal mycangium: Xylosandrus amputatus, Xylosandrus compactus, Xylosandrus crassiusculus, Xylosandrus discolor, and Xylosandrus germanus. We processed 181 beetle samples from the United States and China. All five species displayed three stages of the mycangium development: (1) young teneral adults had an empty, deflated and cryptic mycangium without fungal mass; (2) in fully mature adults during dispersal, the pro-mesonotal membrane was inflated, and most individuals developed a mycangium mostly filled with the symbiont, though size and symmetry varied; and (3) after successful establishment of their new galleries, most females discharged the bulk of the fungal inoculum and deflated the mycangium. Experimental aposymbiotic individuals demonstrated that the pronotal membrane invaginated independently of the presence of the fungus, but the fungus was required for inflation. Mycangia are more dynamic than previously thought, and their morphological changes correspond to the phases of the symbiosis. Importantly, studies of the fungal symbionts or plant pathogen transmission in ambrosia beetles need to consider which developmental stage to sample. We provide illustrations of the different stages, including microphotography of dissections and micro-CT scans.

Toxicity to, oviposition and population growth impairments of Callosobruchus maculatus exposed to clove and cinnamon essential oils.

The use of plant essential oils has been shown to efficiently control insect pests of stored beans, significantly reducing the threats associated with synthetic insecticides. Here, we evaluated the potential of applications of essential oils of clove, Syzygium aromaticum L., and cinnamon, Cinnamomum zeylanicum L., to control Callosobruchus maculatus, considered as one of the most cosmopolitan pests of stored beans. Using four combinations of couples (i.e., unexposed couples, exposed females, exposed males, and exposed couples), we also evaluated how sublethal exposure to these essential oils impacted C. maculatus oviposition. Bioassays results revealed that both essential oils exhibited insecticidal activities similar to the synthetic pyrethroid insecticide deltamethrin. Furthermore, oil dosage increments proportionately decreased the growth rate and reduced the losses in bean weight caused by cowpea weevils, and offspring emergence was almost abolished when parents were exposed to the LD20 of each essential oil. Finally, significant oviposition impairments were perceived only in couples where females were exposed (i.e., females exposed and exposed couples) to the LD20 of cinnamon and clove essential oils. Thus, by exhibiting similar insecticidal activities as synthetic insecticides and by significantly affecting the oviposition of sublethally exposed C. maculatus females, the cinnamon and clove essential oils represent valuable tools with potential of integration into the management of C. maculatus infestations.