A molecular phylogeny of rose chafers (Coleoptera: Scarabaeidae: Cetoniinae) reveals a complex and concerted morphological evolution related to their flight mode

The first report of complete mitogenomes of two endangered species of genus Propomacrus (Coleoptera: Scarabaeidae: Euchirinae) and phylogenetic implications

To understand the mitochondrial genome structure of two endangered and long-armed scarab beetles, Propomacrus davidi and Propomacrus bimucronatus, their complete mitogenomes were sequenced for the first time in this study. The complete mitogenomes of P. davidi and P. bimucronatus were 18, 042 bp and 18, 104 bp in length, respectively. The gene orders of their mitogenomes were highly consistent with other Coleopteran species, and the typical ATN was used as the start codon in most protein coding genes. The incomplete stop codon T was used in cox1, cox2, and nad5, and TAN was used as a complete stop codon in most protein coding genes. All predicted tRNAs could form a typical cloverleaf secondary structure, except that trnS1 lacked the dihydrouridine arm. Based on the maximum likelihood and the Bayesian inference methods, phylogenetic trees of 50 species were reconstructed. The results showed that P. davidi, P. bimucronatus, Cheirotonus jansoni and Cheirotonus gestroi clustered in the same branch, and were the most closely related. The results supported that subfamily Euchirinae is a monophyletic group of Scarabaeidae, which was consistent with the morphological classification. These molecular data enriched the complete mitogenome database of Euchirinae, and improved our understanding of the phylogenetic relationship and evolutionary characteristics of these two endangered species.

A Cretaceous Chafer Beetle (Coleoptera: Scarabaeidae) with Exaggerated Hind Legs-Insight from Comparative Functional Morphology into a Possible Spring Movement

The phenomenon of exaggerated morphological structures has fascinated people for centuries. Beetles of the family Scarabaeidae show many very diverse exaggerated characters, for example, a variety of horns, enlarged mandibles or elongated antennal lamellae. Here, we report a new Mesozoic scarab, Antiqusolidus maculatus gen. et sp. n. from the Lower Cretaceous Yixian Formation (~125 Ma), which has unusually robust and structured hind legs with greatly enlarged spurs and a unique elongated apical process. Based on simulations and finite element analyses, the function of these structures is hypothesized to support springing to aid movement and fighting. Based on available morphological characters, we performed phylogenetic analyses (maximum parsimony) of the main subfamilies and families of Scarabaeoidea. The results support the placement of Antiqusolidus gen. n. as a sister group of Rutelinae within the phytophagous lineage of pleurostict Scarabaeidae. Furthermore, the unusual delicate color marking patterns in the fossil specimens suggest that the new species might have been diurnal and potentially visited the leaves or flowers of Early Cretaceous plants. This morphological and functional study on this extinct scarab species provides new sights into exaggerated structures in Mesozoic insects.

Revisiting trends in morphology of antennal sensilla in scarabaeoid beetles

Phytophagous scarab beetles associated with angiosperms have characteristically enlarged lamellate antennae and exhibit a striking morphological variation of sensilla. In this study, we compared the morphology of antennal surface of 62 species Scarabaeoidea using SEM microscopy, particularly also in light of their evolution in association with angiosperms. We investigated the correlation of antennal sensilla morphology, i.e., their structure and distribution, with species diversity and lineage diversification rates. A high diversity of sensilla was observed but also multiple transitional forms, even on the same antennomere. We interpreted this as evidence for a high evolutionary plasticity. We recognized clear patterns of convergence and repeated evolution of certain types of placoid sensilla. One main tendency found in the phytophagous Pleurostict chafers was a shift from sensilla trichodea to placoid-like sensilla, apparently also enhanced by the increase of the lamellate antennal surface, either by size or number of the lamellae. This trend occurred not only in the Pleurosticts, but also in Glaphyridae, a second angiosperm-associated lineage of Scarabaeoidea. However, our results suggest no direct relation between species diversity or the rate of diversification and general sensilla morphology, i.e., the origin of placoid sensilla. This could be explained not only by species-poor lineages also possessing placoid sensilla but also by otherwise successful and species rich groups having sensilla trichodea (e.g., dung beetles). Results further reveal the need to refine current phylogenetic hypotheses by more comprehensive taxon sampling and to expand the molecular characterization of pheromones and odor binding proteins to better understand the role of chemical communication in scarab diversification.

Phylogenetic position and morphological polymorphism of the chafer, Clinterocera nigra (Coleoptera: Scarabaeidae: Cetoniinae) from Taiwan

Three mitochondrial genomes of the cetoniine beetle, Clinterocera nigra (Kano, 1931) were assembled via next-generation sequencing. The newly sequenced mitogenomes all have 37 genes, showing standard gene order and annotation as the other insects. To examine their phylogenetic positions and relationships between their elytral color (red-spot and melanistic forms) and sequence variation, a total of 118 public mitogenomes of Scarabaeidae were used to infer a maximum-likelihood (ML) tree. Our results show that the melanistic form is grouped within red-spot ones, revealing a population level variation on the elytra color. Our work also provides the first mitogenomic reference of myrmecophilous chafers.

Functional Morphology of the Thorax of the Click Beetle Campsosternus auratus (Coleoptera, Elateridae), with an Emphasis on Its Jumping Mechanism

Simple Summary

Click beetles are well-known for the specialized thoracic structure, which they can click to thrust themselves into the air and to right themselves. Several aspects of their jumping mechanism were still not entirely clear prior to this study. We utilized traditional dissection, 3D virtual dissection, and high-speed filming techniques to investigate the functional morphology of their thorax. Our results show several new insights into their extraordinary clicking and jumping mechanisms.

Abstract

We investigated and described the thoracic structures, jumping mechanism, and promesothoracic interlocking mechanism of the click beetle Campsosternus auratus (Drury) (Elateridae: Dendrometrinae). Two experiments were conducted to reveal the critical muscles and sclerites involved in the jumping mechanism. They showed that M2 and M4 are essential clicking-related muscles. The prosternal process, the prosternal rest of the mesoventrite, the mesoventral cavity, the base of the elytra, and the posterodorsal evagination of the pronotum are critical clicking-related sclerites. The destruction of any of these muscles and sclerites resulted in the loss of normal clicking and jumping ability. The mesonotum was identified as a highly specialized saddle-shaped biological spring that can store elastic energy and release it abruptly. During the jumping process of C. auratus, M2 contracts to establish and latch the clicking system, and M4 contracts to generate energy. The specialized thoracic biological springs (e.g., the prosternum and mesonotum) and elastic cuticles store and abruptly release the colossal energy, which explosively raises the beetle body in a few milliseconds. The specialized trigger muscle for the release of the clicking was not found; our study supports the theory that the triggering of the clicking is due to the building-up of tension (i.e., elastic energy) in the system.

The rose chafers (Coleoptera: Scarabaeidae: Cetoniinae) of Guinea-Bissau: an annotated checklist and new records

An annotated checklist of the species and subspecies of rose chafers (Scarabaeidae: Cetoniinae) hitherto known from Guinea-Bissau is given. This list includes historical and published species records, but also novel information from several entomological expeditions/missions to that country carried by the author (1983, 1992, 1995, 2006 and 2009). A total of 49 species and 3 subspecies are recorded for Guinea-Bissau. Endemic taxa are unknown for the country and some native species were recorded based on a single specimen only (some without precise locality data). Five genera and thirteen species are reported for the first time from Guinea-Bissau in this study. A historical review, as well as some considerations on the distribution and conservation status of these beetles in Guinea-Bissau is also presented.  

Antennal sensilla in Cyclocephala literata Burmeister, 1847 (Coleoptera: Scarabaeidae: Dynastinae)

Abstract: Adults of the beetle Cyclocephala literata Burmeister, 1847 are important pollinators to some Magnoliaceae. Is known that insects could find host plants by detecting volatiles through antennal sensilla. Cyclocephala has its three distal antennomeres lamellate, and the surface of each lamella has sensilla trichodea, chaetica, placodea, coeloconica, basiconica and ampullacea. Three kinds of sensilla placodea were found (type I, II and III), and two kinds of sensilla coeloconica were observed (type I and II). Females have on average 10,776 sensilla, of which 10,214 are sensilla placodea, 536 are sensilla coeloconica, and 26 are sensilla basiconica. Males have on average 10,386 sensilla, of which 9,873 are sensilla placodea, 464 are sensilla coeloconica, and 49 are sensilla basiconica. Males and females have similar quantities of sensilla, and sensilla placodea are predominant. The differences observed in the number of sensilla of males and females were found in other beetles and were attributed to the detection of cospecific sexual pheromones by one of the sexes, or to the detection of plant volatiles. The antennal sensilla of C. literata is described and quantified in present study, and some perspectives about the differences kind of chemical communication, pollination, and antennae dimorphism is discussed.

Larval chaetotaxy and morphology are highly homoplastic yet phylogenetically informative in Hydrobiusini water scavenger beetles (Coleoptera: Hydrophilidae)

Phylogenetic analyses testing the monophyly of the tribe Hydrobiusini and the relationships among its genera are performed based on a data matrix including characters of larval morphology and morphometrics, larval chaetotaxy and adult morphology, including eight of the nine hydrobiusine genera plus 15 outgroup taxa. The head chaetotaxy of six genera of the tribe Hydrobiusini is described (Ametor, Hybogralius, Hydramara, Limnohydrobius, Limnoxenus and Sperchopsis). Morphometric characters derived from the head capsule and mouthparts are included. All characters are illustrated in detail. The analyses performed on the above datasets and their combinations reveal the monophyly of the Hydrobiusini except for Hybogralius, and reconstruct the internal topology of the tribe, largely corresponding to results of previous molecular analyses. Hybogralius groups with genera having larvae adapted to underwater feeding in all analyses. The position of the genus Tritonus within the Laccobiini is questioned by our analyses, which suggest a closer relationship with the tribes Hydrophilini or Hydrobiusini. Larval characters are revealed as highly homoplastic, with chaetotaxic characters performing slightly worse than usual larval morphology. Nonetheless, they are phylogenetically informative and useful for testing phylogenetic hypotheses resulting from analyses of molecules or adult morphology. A key to larvae of the genera of the Hydrobiusini is presented.

Morphological description of the third instar larva of Lasiotrichius succinctus hananoi (Sawada) (Coleoptera: Scarabaeidae: Cetoniinae: Trichiini), using scanning electron microscopy

Cetoniinae is one of the showiest scarab groups, exhibiting bright-metallic body colors, and usually attract great attention from entomologists and amateur collectors. Larvae of Cetoniinae show dramatically diversity on morphology and living habits. Although being considered one of the best-studied groups of Scarabaeidae, larvae have been described for less than 5% species to the known Cetoniinae. In this study, the final instar larva of Lasiotrichius succinctus hananoi was described using scanning electron microscopy. The larvae are peculiar for bearing a haptomeral process dividing 10 spines into two groups: six on the left side, four on the right side, different from the previous descriptions on L. succinctus (Pallas, 1781). The morphological differences under SEM imply the further requirement of taxonomic revision in Lasiotrichius. Both advantage and disadvantage of SEM utilizing in larval descriptions were briefly discussed.

Hiding in plain sight: DNA barcoding suggests cryptic species in all ‘well-known’ Australian flower beetles (Scarabaeidae: Cetoniinae)

DNA barcode data is presented for Australian cetoniine flower beetles to aid with species discovery and guide revisionary taxonomy. Sequences of the COI gene’s DNA barcode region were acquired from 284 cetoniine specimens, covering 68 described species and 33 genera. This equates to 48% of the known species and 83% of the genera which occur in Australia. Results suggest up to 27 putative undescribed species in our sample, only 11 of which were suspected to be undescribed before this study, leaving 16 unexpected (“cryptic”) species. The Australian cetoniine fauna may hence be increased by up to 19%. An unanticipated result of the work is that each of the five most visible and commonly collected Australian cetoniine species, Eupoecila australasiae (Donovan, 1805), Neorrhina punctatum (Donovan, 1805), Glycyphana (Glycyphaniola) stolata (Fabricius, 1781), Chondropyga dorsalis (Donovan, 1805) and Bisallardiana gymnopleura (Fischer, 1823), have unexpectedly high diversity in DNA barcode sequences and were consequently split into multiple clusters, possibly indicating the presence of cryptic species.

Morphological diversification has led to inter-specific variation in elastic wing deformation during flight in scarab beetles

Insect wing shapes and the internal wing-vein arrangement are remarkably diverse. Although the wings lack intrinsic musculature to adjust shape actively, they elastically deform due to aerodynamic and inertial loads during flapping. In turn, the deformations alter the shape of the wing profile affecting the aerodynamic force. To determine how changes in wing-vein arrangement affect elastic wing deformation during free flight, we compared elastic wing deformations between free-flying rose chafers (Protaetia cuprea) and dung beetles (Scarabaeus puncticollis), complementing the comparison with wing static bending measurements. The broader relevance of the results to scarab beetle divergence was examined in a geometric morphometric (GM) analysis of wing-vein arrangement in 20 species differing in phylogeny and ecology. Despite rose chafers and dung beetles demonstrating similar flapping kinematics and wing size, the rose chafer wings undergo greater elastic deformation during flapping. GM analyses corrected for phylogenetic relatedness revealed that the two beetles represent extremes in wing morphology among the scarab subfamilies. Most of the differences occur at the distal leading edge and the proximal trailing edge of the wing, diversifying the flexibility of these regions, thereby changing the pattern of elastic wing deformation during flapping. Changes to local wing compliance seem to be associated with the diversification of scarab beetles to different food sources, perhaps as an adaptation to meet the demands of diverse flight styles.

New species of Xiphoscelis Burmeister, 1842 (Coleoptera, Scarabaeidae, Cetoniinae) from arid regions of South Africa and Namibia

Two new species of the southern African genus Xiphoscelis Burmeister, 1842 are recognised and described, X.braunsisp. nov. from the Eastern and Western Cape Karoo (South Africa) and X.namibicasp. nov. from the Huns Mountains of southern Namibia and adjacent ranges in South Africa. These were previously overlooked and grouped together with X.schuckardi Burmeister, 1842, but further material and more in-depth analyses have now revealed their clear separation on the basis of key diagnostic features, including clypeal structure, metatibial spur development and aedeagal shape. The densely and coarsely costate elytral structure and the black to brown colour of these species are symplesiomorphies shared with a number of the most primitive genera among the African Cetoniinae. However, these characters also reflect the convergent adaptation to hot and arid conditions they share with several other species occurring in this region. Phylogenetic relationships of the genus with other Cetoniinae are explored using the larval characters highlighted in the description of the 3^rd instar larva of X.braunsisp. nov. The extraordinary hypertrophy observed in the male metatibial spur of species in this genus, and particularly in X.schuckardi, appears to represent a defence mechanism against potential predators on the ground, apart from playing a role during mating.

Description of a new species of Rhinocoeta Burmeister, 1842 (Scarabaeidae, Cetoniinae) from the South African Northern Cape

Rhinocoetanamaquasp. nov. is recognised as a separate species from its closest relative, R.cornuta (Fabricius, 1781) after a review and close analysis of specimens recently collected in the semiarid region of the Northern Cape Province, South Africa. The new species can be readily separated from R.cornuta by the drastically reduced tubercle and associated depression on its anterior pronotal margin, particularly in the male. In addition, the general body shape of R.namaqua is more globose than that of R.cornuta, its average total length is larger, and its elytral costae are generally reduced and poorly visible, particularly at the level of the umbones. These characteristics make it practically impossible to separate the two sexes of R.namaqua, without inspection of the internal reproductive organs, as their external morphologies are virtually identical, unlike in R.cornuta. Finally, the aedeagal parameres of R.namaqua exhibit a narrower apex than those of R.cornuta and, in particular, lack the subapical hook-shaped lateral expansions that are so typical of all the other Rhinocoeta s. str. species. The new species appears to be restricted to specific bioregions of the Succulent and Nama Karoo biomes of the Northern Cape, and like all other species of the genus is generally found on or under mammal herbivore dung. Adult activity is limited to short periods immediately after rainfall events, during which individuals fly around and mate, but do not feed on either fruits or flowers.

Importance of Urban Parks in Conserving Biodiversity of Flower Chafer Beetles (Coleoptera: Scarabaeoidea: Cetoniinae) in Brazilian Cerrado

The Brazilian Cerrado, a hotspot and the largest savannah in the world, has been undergoing intense changes in land use for urbanization. The creation and maintenance of urban parks and public squares is one efficient biodiversity conservation strategy in urbanized landscapes. In this study, our objective was to evaluate the potential of urban parks with native vegetation for conservation of flower chafer beetles (Coleoptera: Cetoniinae), a beetle group usually used as a bioindicator in African landscapes, in Brazilian Cerrado. We sampled Cetoniinae beetles using aerial fruit-baited traps, every 2 wk from January to December 2014 in 10 areas of Cerrado in Aquidauana, MS, Brazil. We compared the species richness, abundance, biomass, and species composition between six 'natural reserve' areas (outside the urban matrix) and four 'urban park' areas (within the urban matrix), and identified specialist species of each habitat type. A total 508 individuals of nine species were captured. The abundance, species richness, and biomass were similar between natural reserve and urban park. However, species composition differed among the habitats. Gymnetis flava (Weber) was classified as an urban park specialist, while Euphoria lurida (Fabricius), and Hoplopyga liturata (Olivier) were classified as natural reserve specialists. Our results demonstrate that urban parks conserve the abundance, biomass and species richness of flower chafer beetles in the Brazilian Cerrado. In this context, our results suggest that the maintenance of the urban park with native vegetation can be an efficient strategy for the conservation of Cetoniinae beetles in the urban matrix in the Brazilian Cerrado.

Morphology of the elytral base sclerites

The elytral base sclerites (= sclerites located at the articular region between the forewing and thorax in Coleoptera) of selected taxa were examined and homologized. Although the elytral base sclerites are highly modified compared to the wing base sclerites of the other neopterans, they can be homologized by using the conservative wing flapping and folding lines as landmarks. A reduction of the first axillary sclerite was identified as a general trend of the elytral base sclerites, although the sclerite usually has a very important function to mediate flight power from the notum to the wing. This result indicates that the functional constraint against the basal sclerites is relaxed because of the lack of an ability to produce flight power by elytra. In contrast, the elytral folding system formed by the basal sclerites is well retained, which probably occurs because proper wing folding is a key for the shelter function of the elytra. The elytral base sclerites apparently contain more homoplasies than the serially homologous hindwing base sclerites of Coleoptera, which suggests that the structure is less useful for higher-level systematics. However, the faster evolutionary rate of the elytral base sclerites suggests there is potential for studying the lower-level phylogeny of Coleoptera.