Redescription of the tiger beetle Cicindelidia aeneicollis (Bates 1881) (Coleoptera: Cicindelidae) and discovery of new morphological variants from the Pacific Slope of Mexico.

The tiger beetle species, Cicindelidia aeneicollis (Bates 1881) is redescribed, as Bates original description was inadequate and did not accurately capture the character states or variation found within the species. The specific epithet aeneicollis is partially misleading as the proepisternum is mostly aeneous (bronze/copper) with the basal quarter to third being polychromatic, which the description does not convey. Some populations of this species from the western coast of Mexico exhibit significant variation in maculations, with individuals ranging from weakly marked (as in Bates description) to much more extensively marked.

A distinctive new species of Protozantaena Perkins, 1997 from lowland Namaqualand, South Africa (Coleoptera, Hydraenidae).

Protozantaena gigantea sp. nov. is described, based on specimens collected from residual pools in a drying seasonal river in Namaqualand, Northern Cape Province, South Africa. Morphologically, the new species appears to be related to P. labrata Perkins, 1997 from Namibia and P. birdi Bilton, 2022, from the Great Escarpment in the Eastern Cape Province. At up to 2.0 mm in body length, the new species, whilst small, is by far the largest African Protozantaena Perkins, 1997 known to date. The opportunity is also taken to report a new record for P. birdi in the Eastern Cape Drakensberg.

Hydroporus queneyi sp. n. from southern France, a new semi-subterranean diving beetle of the Hydroporus normandi-complex (Coleoptera, Dytiscidae, Hydroporini).

Hydroporus queneyi sp. n. is described from the area of Montpellier in southern France. It is a member of the Hydroporus normandi-complex (within the H. memnonius-group) and shares with other species of the complex the typical suite of morphological features associated with a semi-subterranean ecology. The new species differs from all previously known species of the complex by the antennomeres VXI distinctly darkened, and by a diagnostic combination of features notably of the habitus, surface sculpture and pubescence, aspect of the metacoxal lines and posterior wing venation. Its morphology is compared with that of related species, as well as described and illustrated. Collecting circumstances for the new species are described and an updated map of the distribution of H. normandi-complex species is provided. Newly produced partial sequences of the mitochondrial marker CO1 from specimens of H. queneyi sp. n., H. galloprovincialis Manuel, 2013 and two subspecies of H. normandi Rgimbart, 1903 were analysed together with publicly available sequences. In the resulting CO1 tree, haplotypes from the respective morphospecies are well separated within the H. normandi-complex, and H. queneyi sp. n. is positioned closer to the Balearic Islands endemic H. lluci Fery, 1999 than to its continental relatives H. galloprovincialis and H. normandi.

Morphological and structural characteristics of the elytra reduce impact damage to ladybird beetles.

Beetle elytra act as natural protective covers and effectively shield their flexible abdomens and fragile hindwings from damage. The existing studies have attributed this contribution of the elytra to its honeycomb structures. In this combined experimental and theoretical study, we used the seven-spotted ladybird beetle to demonstrate that both biological morphology and the hollow structure of the dome-like elytra combined to reduce damage during falling. The falling ladybird beetles had a high probability (59.52%) of hitting the ground with the costal edge of the elytra. This strategy could assist with converting the translational energy into rotational kinetic energy, resulting in the reduction of the impulse during falling. In addition, the hollow structures on the elytra could further absorb the residual impact energy. In the future, this biological paradigm could be used as a basis for the development of falling/landing techniques for advanced robots.

Rhinoceros beetle (Trypoxylus dichotomus) cuticular hydrocarbons contain information about body size and sex.

Japanese rhinoceros beetle (Trypoxylus dichotomus) males have exaggerated horns that are used to compete for territories. Larger males with larger horns tend to win these competitions, giving them access to females. Agonistic interactions include what appears to be assessment and often end without escalating to physical combat. However, it is unknown what information competitors use to assess each other. In many insect species chemical signals can carry a range of information, including social position, nutritional state, morphology, and sex. Specifically, cuticular hydrocarbons (CHCs), which are waxes excreted on the surface of insect exoskeletons, can communicate a variety of information. Here, we asked whether CHCs in rhinoceros beetles carry information about sex, body size, and condition that could be used by males during assessment behavior. Multivariate analysis of hydrocarbon composition revealed patterns associated with both sex and body size. We suggest that Rhinoceros beetles could be communicating information through CHCs that would explain behavioral decisions.

Morphometric analysis for determination of larval instars in Dermestes frischii Kugelann and Dermestes undulatus Brahm (Coleoptera: Dermestidae).

Dermestes frischii Kugelann, 1792 and Dermestes undulatus Brahm, 1790 are the most abundant species worldwide at outdoor or indoor crime scenes during the dry and skeletal stages of decomposition. The attribution of larval age in these beetles is problematic due to the variable number of instars, which is influenced by environmental factors. In this study, a morphometric approach was used to look for potential morphological features as evidence of larval stages. Breeding and monitoring were performed for both species in an incubator with a preset temperature of 28°C ± 0.5 without a photoperiod. Morphometric measurements were made on 10 larvae per instar for each species using length, width, and thickness parameters. Linear discriminant analysis was then used to generate decision boundaries that clearly separated larval stages. The cross-validation procedure demonstrated that the morphometric approach successfully discriminated adjacent larval stages in both species with high values of sensitivity and specificity. This less-invasive approach could improve the ability to estimate minPMI in forensic studies of Dermestidae beetles. Future studies may extend this approach to other species and establish good practices for collecting and storing specimens for morphometric analysis.

Morphological and genetic differences in legs of a polygamous beetle between sexes, Glenea cantor (Coleopter: Cerambycidae: Lamiinae).

The legs of insects play an important role in their daily behaviour, especially reproduction. Entomologists have performed much research on the role of the leg in different behaviours of beetles, an important group in the insect family, but relatively little has been done to study the ultrastructure and transcriptome of their legs. Hence, we systematically studied the ultrastructure and gene expression of the leg of G. cantor, a polygynous beetle, and compared its male and female diversity. In this study, we found the fore-leg, mid-leg and hind-leg of the female were significantly longer than those of the male. From the perspective of intuitive structural differences, we also compared the ultrastructures of the adhesion structure (tarsal) of males and females. The tarsal functional structure of the adult leg mainly includes sensilla and an adhesion structure. The sensilla on the tarsal joint mainly include sensilla chaetica (SCh II, SCh III) and sensilla trichodea (ST II). The adhesion structure includes disc-shaped bristles (di), lanceolate bristles (la), serrated bristles (se), spatula-shaped bristles (spl) and mushroom-shaped bristles (mus). Although there was no significant difference in sensillum distribution or type between males and females, there were significant differences in the distribution and species of adhesion structures between the fore-leg, mid-leg, and hind-leg of the same sex and between males and females. Therefore, different adhesion structures play different roles in various behaviours of beetles. On the other hand, the transcriptome results of male and female legs were screened for a subset of olfaction- and mechanics-related genes. We discovered that the male leg showed upregulation of 1 odorant binding protein (OBP), 2 Olfactory receptors (ORs) and 2 Chemosensory proteins (CSPs). Meanwhile, the female leg showed upregulation of 3 OBPs, 1 OR, 1 Gustatory receptor (GR) and 3 Mechanosensitive proteins (MSPs). An in-depth examination of the ultrastructure and molecular composition of the legs can elucidate its function in the reproductive behavior of G. cantor. Moremore, this investigation will serve as a cornerstone for subsequent research into the underlying behavioral mechanisms.

Morphology and distribution of sensilla on head appendages in the water beetle Hygrobia hermanni (Coleoptera: Adephaga: Hygrobiidae).

Sensilla on head appendages were studied in detail for the first time in a member of the relict family Hygrobiidae (squeak beetles), closely related to Dytiscidae (diving beetles). Adult and third instar larval stage specimens of Hygrobia hermanni (Fabricius, 1775) were examined using scanning electron microscopy, focusing on antennae, palps and larval mandibles. In total, 37 sensilla subtypes are described, including 22 observed in the adult (basiconica: 3; Böhm's bristles: 2; circumvallate sensilla: 2; coeloconica: 10; ovoid placodea: 3; digitiform placodea: 2) and 16 in the larva (basiconica: 4; campaniformia: 1; chaetica: 4; coeloconica: 5; trichodea: 1; unnamed: 1). Only one subtype (of sensilla coeloconica) was shared between the adult and the larva. Autapomorphies of Hygrobiidae and Dytiscidae, and putatively shared derived characters (synapomorphies) of Hygrobiidae + Dytiscidae are discussed. Among the latter, the most remarkable is the acquisition of a special sensory field, located on the apical segment of the adult maxillary palp, subapically and postero-dorsally. This sensory field is made up of ovoid multiporous sensilla placodea otherwise present on the anterior (internal) surface of antennal segments, suggesting that in a common ancestor of Hygrobiidae and Dytiscidae, maxillary palps might have taken over enhanced capacities of longe-range molecule detection.

Morphology of the pygidial glands and chemical composition of their secretions in two species of tiger beetles (Carabidae: Cicindelinae).

Pygidial glands are a common feature of all adephagans and their products play an important role in defense against predators. The morphology of the pygidial glands and the chemistry of their secretion were studied for the first time in two species of tiger beetles - Cicindela (Cicindela) sylvicola Dejean, 1822 and Cylindera (Cylindera) germanica (Linnaeus, 1758). The glands were examined by both bright-field microscopy and nonlinear microscopy. All morphological structures of the glands were measured and described in detail. The structures mentioned were compared with those of related taxa. The secretion extracts from the pygidial glands of the investigated taxa contained a total of 24 compounds, which were detected by gas chromatography-mass spectrometry (GC-MS). The secretion mixture of C. (C.) germanica was more complex (21 chemicals) than that of C. (C.) sylvicola (11 ones). Benzaldehyde was present in both secretion samples. Hydrocarbons were the most abundant group of secretory compounds. The purpose of the compounds, their distribution within the subfamily Cicindelinae and their effects on the ecology of the group were discussed.

Morphology and distribution of sensilla on antennae and mouthparts of the adult bruchid beetles, Bruchidius coreanus (Coleoptera: Bruchidae).

Bruchidius coreanus is a serious pest on Gleditsia sinensis Lam during seed storage, causing significant losses to their yield in southwest China. To gain insight into their behavioral mechanisms, the external morphology, ultrastructure, and distribution of sensilla on antennae, maxillary palps, and labial palps of both male and female B. coreanus were observed using a scanning electron microscope. The results revealed that both male and female adults had serrated antennae comprising a scape, a pedicel, and nine flagellomeres (F1-F9). There were eight types and seven subtypes of antenna sensilla observed in both sexes, including Böhm sensilla (BS), two subtypes of sensilla chaetica (SC1 and SC2), two subtypes of sensilla trichodea (ST1 and ST2), three subtypes of sensilla basiconica (SB1, SB2, and SB3), sensilla auricillica (SA), sensilla styloconicum (SS), capitate pegs (CP), and sensilla cavity (SCa). The average length of BS and ST (ST1 and ST2) showed significant differences between males and females. Furthermore, the number of SC (SC1 and SC2), ST1, and SCa differed significantly between the sexes. Four types of sensilla were found on the maxillary palps and labial palps, with the length of ST on these palps significantly differing between males and females. Additionally, SS on male labial palps was significantly longer than in females. The number of SC significantly differed between the male and female maxillary palps and labial palps, while ST and SS showed significant differences in the maxillary palps. These findings will contribute to further electrophysiological recording and behavioral research. RESEARCH HIGHLIGHTS: The external morphology and distribution of various sensilla on the antennae, maxillary palps, and labial palps of Bruchidius coreanus were described. Eight types and seven subtypes of antenna sensilla were observed on the antennae, while four types of sensilla were observed on the maxillary palps and labial palps. The capitate pegs were found exclusively on the antennae of female B. coreanus.

Differences in three instars of four carrion nitidulids (Coleoptera, Nitidulidae, Nitidula and Omosita) revealed using SEM.

The genera Omosita and Nitidula from the family Nitidulidae, are often reported to be associated with rotten animal carcasses. However, morphological descriptions of their larval stages are limited and are usually only from the third instar larvae, which does not provide enough systematic data. In this study, the overall structure of three instar larvae from the four Nitidulidae species was compared using optical microscopy, and the resolution was not satisfactory. To compensate, a large number of structures and organs were observed by scanning electron microscopy (SEM). Results showed that the number and distribution of chaetotaxy in different parts, including the macrosetae, setae, and microtrichia, have important identification values between the genera, species, and even instars. We also discuss the possible role of microtrichia in the biology of Nitidulidae larvae. Additionally, we described the number and types of sensilla in three sensory organs, and the morphologic parameters of the head capsule and urogomphi as determined by SEM images, are provided. An identification key with application value for storage products and forensic entomology was also compiled.

Strong attachment as an adaptation of flightless weevils on windy oceanic islands.

Enhanced attachment ability is common in plants on islands to avoid potential fatal passive dispersal. However, whether island insects also have increased attachment ability remains unclear. Here we measured the attachment of a flightless weevil, Pachyrhynchus sarcitis kotoensis, from tropical islands, and compared it with documented arthropods from the mainland. We examined the morphology and material gradient of its attachment devices to identify the specific adaptive modifications for attachment. We find that the weevil has much stronger attachment force and higher safety factor than previously studied arthropods, regardless of body size and substrate roughness. This probably results from the specific flexible bases of the adhesive setae on the third footpad of the legs. This softer material on the setal base has not been reported hitherto and we suggest that it acts as a flexible hinge to form intimate contact to substrate more effectively. By contrast, no morphological difference in tarsomeres and setae between the weevil and other beetles is observed. Our results show the remarkably strong attachment of an island insect and highlights the potential adaptive benefits of strong attachment in windy island environment. The unique soft bases of the adhesive hairs may inspire the development of strong biomimetic adhesives.

The cranial apparatus glands of the canthariphilous Pyrochroa coccinea (Coleoptera: Pyrochroidae: Pyrochroinae), and their implications in sexual behaviour.

Some Pyrochroidae species are known as "canthariphilous" for their attraction to cantharidin (CTD), a toxic terpene with anti-predatory effects, produced in nature by only two beetle families (Meloidae and Oedemeridae). It has been demonstrated that males of Neopyrochroa flabellata ingesting CTD are positively selected by females. Indeed, the compound is re-emitted from a glandular cranial apparatus as secretions that are licked up by females during courtship behaviour, inducing copulation. Herein, we provide the first description of the glands associated to the cranial apparatus of male Pyrochroinae using the European species Pyrochroa coccinea as a model. Morphological analyses show that the cranial apparatus consists of a concave pit lined with short setae retaining secretions emitted through numerous glandular pores. Ultrastructural investigations reveal the presence of two different class 3 glands (Gl.A and Gl.B), intermixed at the level of the pit but exhibiting distinct features. Gl.A are mainly characterised by short conducting canals, rounded nuclei and electrondense vesicles while Gl.B are characterised by long conducting canals, irregular nuclei, vesicles containing a particulate substance and a multifolded plasma membrane. Observations of sexual behaviour are also reported for P. coccinea and compared to N. flabellata, confirming the involvement of cranial apparatus secretions in courtship behaviour.

Functional morphology of the mouthparts of longhorn beetle adult Psacothea hilaris (Coleoptera: Cerambycidae) and sensilla comparisons between the sexes.

Psacothea hilaris is an important wood boring beetle that causes significant ecological and economic damage. The mouthparts of P. hilaris contain feeding and sensory structures that play important roles in many behaviors. The study of their functional morphologies provides insight into feeding and sensory mechanisms. The fine structures of the mouthparts and the sensilla of both sexes were observed by scanning electron microscopy, with special attention to quantitative comparisons. The general structures of the mouthparts are similar in males and females. However, the maxillary and labial palps of females are more well-developed than those of males. Six types of sensilla were found in both sexes: sensilla basiconca, sensilla trichodea, sensilla chaetica, sensilla digitiformia, sensilla coeloconica, and sensilla palmata. This was the first attempt to describe the sensilla on the epipharynx and ligula of Cerambycidae. There were differences in the number of sensilla of males and females, especially on the mandibles, maxillary and labial palps. However, not all types of sensilla have a greater number in females compared to males. The results provide basic information on the gustatory sensation mechanism of Cerambycidae.

Evolution of horn length and lifting strength in the Japanese rhinoceros beetle Trypoxylus dichotomus.

What limits the size of nature's most extreme structures? For weapons like beetle horns, one possibility is a tradeoff associated with mechanical levers: as the output arm of the lever system-the beetle horn-gets longer, it also gets weaker. This "paradox of the weakening combatant" could offset reproductive advantages of additional increases in weapon size. However, in contemporary populations of most heavily weaponed species, males with the longest weapons also tend to be the strongest, presumably because selection drove the evolution of compensatory changes to these lever systems that ameliorated the force reductions of increased weapon size. Therefore, we test for biomechanical limits by reconstructing the stages of weapon evolution, exploring whether initial increases in weapon length first led to reductions in weapon force generation that were later ameliorated through the evolution of mechanisms of mechanical compensation. We describe phylogeographic relationships among populations of a rhinoceros beetle and show that the "pitchfork" shaped head horn likely increased in length independently in the northern and southern radiations of beetles. Both increases in horn length were associated with dramatic reductions to horn lifting strength-compelling evidence for the paradox of the weakening combatant-and these initial reductions to horn strength were later ameliorated in some populations through reductions to horn length or through increases in head height (the input arm for the horn lever system). Our results reveal an exciting geographic mosaic of weapon size, weapon force, and mechanical compensation, shedding light on larger questions pertaining to the evolution of extreme structures.

Microscopic morphology and distribution of the antennal sensilla in the double-spined bark beetle, Ips duplicatus (Coleoptera: Curculionidae).

The double-spined spruce bark beetle, Ips duplicatus, has become an infamous secondary pest of Norway spruce, causing extensive ecological and economic destruction in many Central European countries. Antennae are the primary olfactory organs that play a fundamental role in insect-host chemical communication; therefore, understanding morphology is crucial before conducting electrophysiological investigations. Here, we present our analysis of sensilla types on the antennal surface of I. duplicatus for the first time, using high-resolution-scanning electron microscopy. We studied the external morphological characteristics of antennae and the types, numbers, and distribution of the antennal sensilla in males and females. Our results revealed the presence of five different types of morphologically distinct sensilla: sensilla chaetica, sensilla basiconica, sensilla trichodea, sensilla coeloconica, and Böhm's sensilla. We observed two subtypes of sensilla chaetica (SChI and SChII), four subtypes of sensilla basiconica (SBI, SBII, SBIII, and SBIV), three subtypes of sensilla trichodea (STrII, STrIII, and STrIV) and two subtypes of sensilla coeloconica (SCoI and SCoII), respectively in I. duplicatus males and females. Minor differences in length and numbers between the sexes for some sensilla types were found. Distribution maps for different sensillar types were constructed, and specific areas for the respective sensilla were found. Possible functions of observed sensilla types are discussed. The present study provides a basis for future electrophysiological studies to understand how I. duplicatus detects ecologically important olfactory cues. RESEARCH HIGHLIGHTS: • The first report of morphology and distribution pattern of the antennal sensilla in Ips duplicatus is discussed. • A total of 6 main types and 11 antennal sensilla subtypes were observed in male and female Ips duplicatus. • Minor sex-specific differences were seen in the length and numbers in several sensilla types.

Redescription and a new record of Centrophthalmus sinensis Raffray, 1904(Coleoptera: Staphylinidae: Pselaphinae).

A new record of Centrophthalmus sinensis Raffray, 1904 from Suzhou, East China is provided, which is also the first Pselaphinae known to occur in this city, and the third pselaphine species from Jiangsu Province. A redescription of the species is given, aided with illustrations of the habitus and other morphological details.

Two new species of Paraneseuthia Franz from Okinawa-jima (Coleoptera, Staphylinidae, Scydmaeninae).

Only one (recently discovered) nominal species of the eutheiine genus Paraneseuthia Franz is known to occur on the largest Ryukyuan Island of Okinawa-jima, while five other members of this rare genus inhabit Ishigaki-jima, Shikoku, Kyushu and Honshu. Undescribed species known from females only have been collected also on southwestern Iriomote-jima and northeastern Hokkaido. Two new Okinawan species are described: P. uminzo sp. n. and P. umisatu sp. n., suggesting that the diversity of Paraneseuthia in the Ryukyus is still known fragmentarily and new discoveries can be expected in other forested southern islands.

The very rare Japanese endemic diving beetle Japanolaccophilus niponensis (Kamiya, 1939), (Coleoptera: Dytiscidae, Laccophilinae): larval morphology and phylogenetic comparison with other known Laccophilini.

The three larval instars of Japanolaccophilus niponensis (Kamiya, 1939) (Coleoptera: Adephaga, Laccophilinae) are described for the first time according to the now genevralized larval descriptive format of Dytiscidae (Coleoptera: Adephaga), which incorporates detailed chaetotaxic and morphometric analyses. A parsimony analysis based on larval characteristics of 14 Laccophilini species in seven genera was conducted using the program TNT. One of the main results is that Japanolaccophilus Satô, 1972, which so far was treated as being related to Neptosternus Sharp, 1882 now stands out as sister to Laccophilus Leach, 1815, and Philodytes J. Balfour-Browne, 1938 with strong support. Additionally, Laccomimus Toledo & Michat, 2015, and Africophilus Guignot, 1948 are resolved as monophyletic and sister to a clade which itself is subdivided into two well supported clades: Neptosternus + Australphilus Watts, 1978, and Japanolaccophilus + (Laccophilus, Philodytes). Philodytes is here newly accepted as junior synonym of Laccophilus.

Morphological and organic spectroscopic studies of a 44-million-year-old leaf beetle (Coleoptera: Chrysomelidae) in amber with endogenous remains of chitin.

This study details the quality of preservation of amber deposits in the Eocene. Through Baltic amber crack-out studies using Synchrotron Micro-Computed Tomography and Scanning Electron Microscopy it was found that the cuticle of a specimen of leaf beetle (Crepidodera tertiotertiaria (Alticini: Galerucinae: Chrysomelidae)) is exceptionally well preserved. Spectroscopic analysis using Synchrotron Fourier Transform Infrared Spectroscopy suggests presence of degraded [Formula: see text]-chitin in multiple areas of the cuticle, and Energy Dispersive Spectroscopy supports the presence of organic preservation. This remarkable preservation is likely the result of several factors such as the favourable antimicrobial and physical shielding properties of Baltic amber as compared to other depositional media, coupled to rapid dehydration of the beetle early in its taphonomic process. We provide evidence that crack-out studies of amber inclusions, although inherently destructive of fossils, are an underutilised method for probing exceptional preservation in deep time.