Eversible exocrine glands play a central role in chemical defence and signalling in insect larvae, yet their fine morphology remains poorly understood because these structures are normally retracted and difficult to observe. In sawflies (Hymenoptera: Tenthredinidae), particularly within Nematinae, chemical composition and defensive function of ventral eversible glands have been well documented, whereas ultrastructural information on the exposed gland surface has been lacking. Here, an approach was developed to stabilize the eversible gland of Nematus japonicus (Takeuchi 1921) larvae in its everted state, enabling detailed examination using scanning electron microscopy. The everted gland surface is characterized by dense cuticular folding without discrete pores or microtrichia, suggesting a thin, weakly sclerotized integument adapted for diffusion-based release of volatile compounds. In addition, a previously unreported sensory field is documented on the larval abdomen, including rows of papilla-like sensilla and dense arrays of sensilla chaetica surrounding the anal slit. These sensory structures are interpreted as components of a coordinated behavioural system involved in faecal expulsion and defensive posture. Together, these findings provide the first ultrastructural characterization of a nematine eversible gland and establish a morphological framework linking gland structure, sensory organization, and defensive behaviour in sawfly larvae.

Larvae of Lepidoptera are predominantly herbivorous, feeding mainly on plant tissues of angiosperms. Some Lithosiini larvae, however, are capable of feeding on lichens, mosses, and algae, forming a distinctive ecological association within Lepidoptera. This study presents the first comprehensive investigation of the biology and larval morphology of Miltochrista pallida, a widespread representative of Asian Lithosiini. Through laboratory rearing and detailed observations under optical and scanning electron microscopy, it was found that the egg stage lasts approximately seven days, while the larval stage spans 21–31 days and consists of five instars. Early instars were observed feeding on moss-covered bark under laboratory conditions, whereas third through fifth instar larvae accepted mulberry leaves in addition to moss. This observation should be interpreted as laboratory feeding acceptance rather than evidence of a natural host plant association. Larvae of M. pallida exhibit several distinctive features, including mandibles with a mola, the presence of secondary setae from the first instar, and uniserial mesoseries crochets. These findings provide new morphological and biological evidence for identifying Lithosiini larvae and contribute to understanding the adaptive evolution of lichen- and moss-feeding strategies within Arctiinae.

Understanding how ecologically similar species coexist remains a central challenge in ecology, particularly in polyphagous assemblages where dietary overlap limits differentiation along a single niche axis. Although coexistence theory emphasizes multidimensional niche partitioning, empirical studies integrating spatial, temporal and dietary dimensions remain scarce. In this study, multidimensional niche partitioning was examined in a community of phytophagous scarab beetles across agricultural fields, forests and grasslands in northeastern China. Habitat-level surveys, fine-scale temporal monitoring, olfactory preference assays and DNA metabarcoding of larval gut contents were combined to quantify niche differentiation across spatial, temporal and dietary dimensions. Species exhibited strong habitat segregation at landscape scale, consistent with habitat filtering as a primary structuring process. Within agricultural habitats where multiple species co-occurred, temporal differentiation reduced but did not eliminate overlap. Gut content composition differed significantly among species, although mean dietary overlap did not differ from null expectation. Patterns of olfactory preference closely corresponded to realized diet composition: species with strong olfactory preferences maintained narrower realized diets, whereas species without strong olfactory preferences exhibited broader and more variable resource use. These results suggest that fine-scale differences in resource use may contribute to niche differentiation among sympatric phytophagous beetles, even when overall dietary overlap remains high. By linking olfactory preference to realized dietary composition, this study highlights how behavioural traits can help explain subtle but consistent differentiation in host use among co-occurring belowground herbivores.

Malpighian tubules are key excretory and osmoregulatory organs in insects, yet their structural organization and hindgut associations remain poorly documented in scarab larvae. In this study, the morphology and ultrastructure of the Malpighian tubules were examined in third-instar larvae of the saprophagous Protaetia brevitarsis, a cetoniine scarab, and the phytophagous Holotrichia diomphalia, a melolonthine scarab, using light and transmission electron microscopy. In both species, four Malpighian tubules are present, originating posterior to the third circle of gastric caeca and arranged in a conserved pattern consisting of two laterally positioned tubules and two ventrally adjacent tubules. The epithelial organization and ultrastructural characteristics of the Malpighian tubules are highly similar between the two species, with principal and stellate cells exhibiting comparable cellular features. In contrast, clear differences were observed in the spatial connection patterns between the Malpighian tubules and the rectum. In P. brevitarsis, the distal ends of the tubules bent posteriorly to form two bilateral pairs connecting to the rectum, whereas in H. diomphalia the tubules joined the rectum at distinct, non-adjacent sites. These findings demonstrate a conserved ultrastructural organization of Malpighian tubules in scarab larvae alongside species-specific variation in hindgut connection patterns, providing new morphological insights into the diversity of rectal complex organization in Coleoptera larvae.

Larvae of Notodontidae employ diverse antipredator strategies, yet research has largely overlooked early instars. In this study, the ultramorphology and chaetotaxy of first-instar Fentonia ocypete were analysed, yielding new evidence for its defensive adaptations and systematic placement. The first-instar larvae of F. ocypete are peculiar for bearing five pairs of dorsal pigmented protuberances on the prothorax, the first three and the eighth abdominal segments, raised anal prolegs bearing reduced crochets and the heterogenetic setal arrangement on A3-A6. The relationship between larval morphology and defensive strategies is briefly discussed.

Eggshells display stable patterns and are able to provide solid basis for insect identification. Notodontidae are usually considered as significant pests for their larvae causing serious damage during outbreaks, underscoring the importance of early and accurate identification. In this study, nine notodontid eggshells from eight genera were compared using cold field emission scanning electron microscopy, in order to discover detailed evidence for the egg identifications. The eggshells exhibit morphological differences on the micropyle area, chorion sculpture, aeropyle density, and polygonal wall details. Notably, the eggshell ornamentations are different between the congeneric species E. splendida and E. cristata, highlighting the potential of eggshell morphology to enhance taxonomic research.

Abstract Larvae of the megadiverse Scarabaeoidea play important economic and ecological roles, and their mouthparts provide valuable morphological clues for species identification and dietary inference. However, the underlying relationships between morphological characters and feeding habits remain insufficiently elucidated. In this study, the larval mouthparts of 22 species representing ten major lineages of Scarabaeoidea were examined in detail. Seventeen characters of the larval mouthparts were analyzed within a phylogenetic framework. Three characters were identified as candidate synapomorphies for the major lineages represented here: maxillary stridulatory teeth for Scarabaeidae, mandibular stridulatory ridges for Cetoniinae + (Dynastinae + Rutelinae), and a circular arrangement of epipharyngeal phobae for Aphodiinae + Scarabaeinae. By contrast, several homoplastic mouthpart traits were recurrently associated with larval feeding habits in the sampled taxa, including a setose acroparia, heli on the epipharynx, and a blade-like incisor region in phytophagous lineages, and the circular phoba complex together with the absence of nesium in coprophagous lineages. These results suggest that larval mouthparts in Scarabaeoidea may retain both phylogenetic and trophic signals, providing a morphological basis for interpreting the evolution of feeding habits in scarab larvae.

Larval identification is crucial for the utilization and management of insect resources, yet morphological studies remain too limited to fulfill this requirement. Flower chafers represent one of the best-studied groups of holometabolous insects in terms of larval morphology, while their adults exhibit highly diverse habits. However, previous research has focused mainly on the larger third instar larvae, offering limited utility for early identification. In this study, we describe and compare the first instar larvae of Cetonia magnifica Ballion, 1871, Gametis jucunda (Faldermann, 1835), Protaetia brevitarsis (Lewis, 1879) and Lasiotrichius succinctus (Pallas, 1781) using scanning electron microscopy (SEM). Distinct morphological characters, including eyespots, nesium, process of haptomerum, scissorial teeth, and palidia on the raster, were highlighted, providing new data to improve early identification within Cetoniinae.

Monolepta hieroglyphica, in view of its wide-ranging host and highly polyphagous characteristics, has become an important agricultural pest in East and Southeast Asian countries. To better understand its biology and develop control strategies, we present a high-quality chromosome-level genome assembly of M. hieroglyphica, with contig N50 of 18.62 Mb and scaffold N50 of 241.916 Mb. Using 156x Hi-C data, we anchored a total length of 2,313 Mb (91.9% of the genome) to nine chromosomes. We predicted 46,561 genes using an integrated approach. The completeness of the final reported genome and proteome were assessed by BUSCO and show high values of 99.4% and 95.2%, respectively. The high-quality chromosome-level genome assembly of M. hieroglyphica will be a useful molecular resource for the communities of both beetle and crop protection.

Dynastinae are among the most diverse groups of scarab beetles, with body sizes ranging from 10 to 225 mm. People often focus on larger male beetles with prominent horns, while smaller species, particularly their larvae, are frequently overlooked. In this study, the final‐instar larvae of Eophileurus chinensis were observed and described using scanning electron microscopy. The larvae are notable for their coarse punctures on the head capsule, paired angular processes on the labrum, a prominent truncate process on the haptomerum, mandibles with a prominent left S4 tooth and a subtle right one, and thoracic claws flattened at the apex. This unique combination of traits distinguishes them from all previously described species. Additionally, the living strategies underlying their relatively small size and life history strategies were briefly discussed.

Mouthparts exhibit diverse morphological features in scarab beetles, resulting from the adaptation to the various living and feeding habits. Adoretini is a small tribe of Rutelinae, remarkable for bearing a beak-like projection on the labrum. However, the correlation between peculiar structures and feeding habits remain unsatisfactory. In this study, the adult mouthparts of Proagopertha lucidula, Anomala corpulenta, Popillia quadriguttata and Adoretus sinicus were compared using scanning electron microscopy, to investigate the structural basis underlying the distinctive feeding behavior of A. sinicus. Based on our investigation, the adult incisors of A. sinicus could not meet when closed. Instead, a beak-like labral projection fits precisely between the paired incisors, which is a configuration markedly different from the other three species. Our scanning electron micrographs reveal distinct wear marks on lateral sides of the labral projections and the mesal corners of mandibular incisors, supporting the hypothesis that both structures are involved in the chewing process. These findings help explain the characteristic perforated damage observed on leaves attacked by Ad. sinicus and also provide a potential functional basis for the labral projection unique to adult Adoretini.

Determining the ecological role of insect larvae is crucial for pest control and resource utilization, which usually relies on accurate species identification. White grubs, the larvae of Scarabaeoidea, exhibit highly diverse behaviors but share a similar morphology, making identification challenging. In this study, an improved six-armed olfactometer was used to test the feeding preferences of two sympatric white grubs, Anomala mongolica and Protaetia brevitarsis. The correlated morphological traits, including the sensory, feeding, and locomotive organs, were investigated using cross-sections and scanning electron microscopy. Our results show that phytophagous grubs possess well-developed antennal sensilla and digitiform sensilla on maxillary palps, mandibles with incisors for cutting plant roots, and fossorial setae and sharp claws on thoracic legs. In contrast, saprophagous grubs have underdeveloped digitiform sensilla, relatively short and robust antennae and thoracic legs, and mandibles lacking cutting edges suitable for severing roots. This study provides new insights for determining the ecological roles of white grubs.

Rhizotrogini are one of the most typical phytophagous scarab beetles, named primarily for their larvae attacking plant roots. Miridiba trichophora is the most widely distributed species of its genus. Its larvae are the main harmful stage and the primary target for control efforts. However, identifying M. trichophora larvae in the field is difficult due to the serious lag in larval classification work. In this study, the larvae of M. trichophora were obtained through rearing and observed using light and scanning electron microscopy. The larvae of M. trichophora are peculiar for the labrum possessing two curved horizonal ridges, the epipharynx equipped with 14 heli and a proplegmatium, the raster furnished with numerous prominent setae pointing the inconspicuous palidia, and the spiracles on the seven- and eighth abdominal segments being comparative larger than the other abdominal spiracles.

Grubs, called Qicao in China, have a long tradition as herbal medicine in East Asia. These larvae belong to the diverse family Scarabaeidae and are typically harvested from the wild during their immature stage based on morphological characteristics. However, rapid and accurate identification becomes challenging when relying solely on external morphological features, as the lack of clarity on biological sources raises safety concerns for clinical applications. The application of DNA metabarcoding provides a solution by enabling the determination of the biological source of a large sample. In the current study, we collected 19 batches of Grubs, consisting of 11,539 individuals, from the market and analyzed their biological composition through metabarcoding. We identified 49 Amplicon Sequence Variants (ASVs), 21 of which were Grubs. The 21 ASVs were classified into seven Molecular Operational Taxonomic Units (MOTUs) through species delimitation, which revealed that commercially available Grubs are predominantly sourced from Protaetia brevitarsis seulensis, while species of Rutelinae, Anomala, and Holotrichia were also abundant in some commercial batches. Among the identified ASVs, 28 belonged to non-Grub species and indicated adulteration from different animal families; high abundances of these ASVs were detected for Bombycidae, Tabanidae, and Viviparidae. Our findings underscore the complexity of Grubs' species composition and advocate for a deeper understanding of the wildlife sources contributing to herbal products. This research contributes valuable insights into the molecular identification of Grubs, paving the way for enhanced quality assurance in traditional medicine applications to provide safe and effective medicines for humanity.

Rhizotrogini are one of the most typical phytophagous scarab beetles, named primarily for their larvae attacking plant roots. Miridiba trichophora is the most widely distributed species of its genus. Its larvae are the main harmful stage and the primary target for control efforts. However, identifying M. trichophora larvae in the field is difficult due to the serious lag in larval classification work. In this study, the larvae of M. trichophora were obtained through rearing and observed using light and scanning electron microscopy. The larvae of M. trichophora are peculiar for the labrum possessing two curved horizonal ridges, the epipharynx equipped with 14 heli and a proplegmatium, the raster furnished with numerous prominent setae pointing the inconspicuous palidia, and the spiracles on the seven- and eighth abdominal segments being comparative larger than the other abdominal spiracles.

Acoustic behaviour plays a signi ficant role in insect communications, but is rarely reported in their immature stages. Larvae of Lucanidae bear paired stridulatory organs on their thoracic legs, which could produce sounds as communicational signals. However, the species-speci fic differences on stridulatory organs and acoustic signals are far from fully investigated. In this study, the larval acoustic behaviours of three lucanid species, Lucanus dybowski , Prosopocoilus confucius and P. girafa were recorded and compared for the first time. The sound producing mechanism was described in detail based on video recordings, morphological observations, and acoustic analyses. The larvae of all three species are able to produce sounds by scraping the plectrum on the metatrochanter against the pars stridens on the mesocoxa during disturbance. The sounds exhibit species-speci fic differences in terms of acoustic parameters: the larvae of L. dybowski produce short-duration (140-200 ms), single-pulse and lowfrequency (-210 Hz) sounds; P. confucius produce long-duration (500-800 ms), triple-pulse and lowfrequency (-280 Hz) sounds; P. girafa produce long-duration (500-560 ms), double-pulse and lowfrequency (-260 Hz) sounds. The amounts and arrangements of the teeth on stridulatory organs also exhibit differences on speci fic level. The acoustic signals and stridulatory organs were compared using principal component analysis. (c) 2023 Elsevier Ltd. All rights reserved.

Rutelini is one of the largest tribes of Rutelinae, widely distributed but primarily in the New World. Recently, both larvae and adults of Parastasia ferrieri had been discovered in Liaoning Province of northeastern China from the Palearctic realm. The third-instar larvae of P. ferrieri were described using light and scanning electron microscopy in order to discover more morphological characters for larval taxonomy. The larvae of P. ferrieri exhibit remarkable features, including four protuberances on labrum, no helus on epipharynx, two scissorial teeth on each mandible, five stridulatory teeth plus a blunt protuberance on each maxilla, and the obtuse claws on the thoracic legs. The correlation between morphological features and feeding habits is briefly discussed.

Larvae of Melolonthinae (white grubs) are usually considered as serious pests for some of them attacking plant roots and causing great losses of agriculture and forestry. However, not all the white grubs are pest species. In this study, the adult Apogonia cupreoviridis were observed to feed on gramineous grasses and fallen ginkgo leaves, while their larvae were frequently collected in the lawn. The larvae were reared in the laboratory and observed using scanning electron microscopy. The larvae have the plegmatia expanded in the middle; distal antennomere with an apical process bearing one bifurcated sensilla and nine sensilla basiconica on the apex; the palidia are V-shaped and each palidium bearing five to nine pali. The V-shaped palidia are found in the known larvae of Diplotaxini, as to genera Apogonia and Liogenys.

Accurate larval identification is a prerequisite for integrated pest management, but remains a long-term difficulty in insect taxonomy. Previous descriptions are mainly focused on the most disruptive final instar larvae. However, earlier instars especially cross-instar larval morphological comparisons were rarely delivered hitherto. Polyphylla laticollis and Maladera orientalis are pests that damage peanut crops at various developmental stages. The first instar larvae of P. laticollis and the mature larvae of M. orientalis attack peanuts simultaneously and cause different types of damage. In this study, we compared the life histories and larval morphologies through field investigations and scanning electron microscopy (SEM) observations. These cross-instar white grubs are similar in sizes, but exhibit morphological differences on their mouthparts, thoracic legs, anal slits, and rasters. This study presents a novel approach to larval identification, with a goal of generating new insights into integrated pest control practices on white grubs.