Morphological Characterization of the Antennal Sensilla of the Legume Pod Borer, Maruca vitrata (Fabricius) (Lepidoptera: Crambidae).

Maruca vitrata (Fabricius) is an important lepidopteran pest of legumes in the tropics and subtropics. Here, we studied the ultrastructural organization of its antennal sense organs using scanning electron microscopy. The antennae of both sexes of M. vitrata were filiform with the number of flagellar segments varying from 72 to 84. Nine major morphological types of sensilla were observed on male and female antennae: sensilla trichodea (ST), sensilla basiconica (SB), sensilla auricillica (SA), sensilla chaetica (SCh), sensilla coeloconica (SCoe), sensilla cylindrica (SCy), sensilla squamiformia (SSq), sensilla styloconica (SSt), and Böhm sensilla (BS). Three of these sensilla types (SB, SSq, and BS) are newly reported for M. vitrata. Morphological observations revealed that four types are multiporous (ST, SB, SA, and SCoe), two types are uniporous (SCh and SCy), and three types are aporous (SSq, SSt, and BS). The average length of male ST was longer than that of the female. Sensilla cylindrica were observed only on male antennae, indicating sexual dimorphism. This study aims to provide some basic evidence for further studies on the mechanism of insect-plant chemical communication and future semiochemical-based management strategies of the major legume pest M. vitrata.

Report on antennal sensilla of Aphelocheirus ellipsoideus (Hemiptera, Heteroptera, Aphelocheiridae).

The comparative morphology study on antennal sensilla of Aphelocheirus ellipsoideus from the family Aphelocheiridae, carried out with the use of a scanning electron microscope, is provided. Five main types of mechano-, chemo-, and thermo-hygroreceptive sensilla with two subtypes of sensilla basiconica were found and described on their surface, including sensilla trichodea, campaniformia, basiconica, ampullacea, and plate-like. Antennal sensilla of A. ellipsoideus on macropterous and brachypterous forms were different.

Morphology and Distribution of Antennal Sensilla in an Egg Parasitoid Wasp, Anastatus disparis (Hymenoptera: Eupelmidae).

The wasp Anastatus disparis is an egg endoparasitoid of a number of Lepidopteran pest species. To better understand the A. disparis olfactory system, we observed the antennal sensilla of males and females under a scanning electron microscope and quantified their sizes and morphological characteristics. We identified the types of sensilla and counted the numbers and locations of the different types on the dorsal and ventral antennal surfaces. The antennae of A. disparis are geniculate, with flagella that comprise 11 subsegments in females and eight in males. The mean antenna length was 1324.10 ± 52.50 µm in females and 1323.93 ± 65.20 µm in males. Ten sensillum types were identified in both sexes: Böhm bristles (BBs), sensilla trichodea (ST, with subtypes STI and STII), sensilla chaetica (SCh), sensilla basiconica (SB, with subtypes SBI and SBII), sensilla placodea (SP), sensilla coeleoconica (SCo), sensilla grooved peg (SGP), sensilla auricillica (SAu), sensilla campaniformia (SCa), and glandular pores (GPs). The total numbers of BBs, STI, SBII, SCa, SCo, and GPs did not differ significantly between the sexes, whereas the total numbers of SCh, SBI, and SAu were significantly greater in females, and those of STII, SP, and SGP were significantly lower. The types, number, and density of antennal sensilla increased from the base to the end. The possible functions of these sensilla in host-detection behavior are discussed.

The Antennal Sensilla and Expression Patterns of Olfactory Genes in the Lower Termite Reticulitermes aculabialis (Isoptera: Rhinotermitidae).

The insect olfactory system plays pivotal roles in insect survival and reproduction through odor detection. Morphological and physiological adaptations are caste-specific and evolved independently in workers, soldiers, and reproductives in termites. However, it is unclear whether the olfactory system is involved in the division of labor in termite colonies. In the present study, the antennal sensilla of alates, workers, soldiers, nymphs, and larvae of the termite Reticulitermes aculabialis Tsai et Hwang ( Isoptera: Rhinotermitidae) were investigated. Transcriptomes were used to detect olfactory genes, and differential expression levels of olfactory genes were confirmed in various castes by qRT-PCR analysis. Nine types of sensilla were identified on the antennae of R. aculabialis, and soldiers possessed all 9 types. In 89,475 assembled unigenes, we found 16 olfactory genes, including 6 chemosensory protein (CSP) and 10 odorant-binding protein (OBP) genes. These OBP genes included 8 general odorant-binding protein genes (GOBPs) and 2 pheromone-binding protein-related protein (PBP) genes. Five CSP genes were more highly expressed in alates than in workers, soldiers, larvae, and nymphs, and the expression levels of CSP6 were significantly higher in nymphs. Seven GOBP and two PBP genes exhibited significantly higher expression levels in alates, and there were no significant differences in the expression levels of GOBP2 among workers, soldiers, alates, and larvae. These results suggest that alates, as primary reproductives, have unique expression patterns of olfactory genes, which play key roles in nuptial flight, mate seeking, and new colony foundation.

Observations on the Ultrastructure of Antennal Sensilla of Adult Glenea cantor (Cerambycidae: Lamiinae).

The external morphology and distribution of antennal sensilla of Glenea cantor Fabricius were studied with scanning electron microscopy. The antennae of G. cantor were observed to be filiform, consisting of scape, pedicel, and flagellum (nine flagellomeres). Four distinct types of sensory receptors were observed, including sensilla chaetica, sensilla trichodea, sensilla basiconica, and Böhm bristles. Three morphological subtypes of sensilla chaetica were found on the antennae, and sensilla trichodea were also categorized into three morphological subtypes. Sensilla basiconica was grouped into two morphological subtypes that were found on subsegments F2-F9 of the flagellum, and Böhm bristles were only found at the intersegmental joints between the scape and the head and between the scape and the pedicel. The antennae of male and female adults were similar in shape, length, and diameter. However, the length, diameter, distribution, and number of each of the four distinct types of sensilla on the males were significantly different from those on females. The types, lengths, diameters, numbers, and distributions of these sensilla were described, and their possible functions were also discussed. The results indicated that the base and end of an antennal segment have a similar sensillum density, but the middle section sensor density is significantly greater, especially for olfactory and gustatory sensilla, possibly because the joints are more involved in mechanical sensing. The density of sensors is closely related to its sensing function; so, future studies on the biology of olfaction and sexual communication in G. cantor will be facilitated by these observations.

Antennal Olfactory Physiology and Behavior of Males of the Ponerine Ant Harpegnathos saltator.

In comparison to the large amount of study on the communication abilities of females in ant societies and their associated chemical ecology and sensory physiology, such study of male ants has been largely ignored; accordingly, little is known about their olfactory sensory capabilities. To address this, we explored peripheral odor sensitivities in male Harpegnathos saltator by measuring the electrophysiological activity of olfactory sensory neurons within antennal trichoid and coeloconic sensilla using an extracellular recording technique. In an initial trial of 46 compounds, sensilla trichodea responded strongly to two alarm pheromone components, while a limited number of non-hydrocarbon odorants elicited strong responses in sensilla coeloconica. Both sensillar types responded indifferently to 31 cuticular hydrocarbons (CHCs) and synthetic long-chain hydrocarbons (HCs) typically found on insect cuticle. In a search for sensilla responding to CHCs and other compounds, we found some sensilla that responded to synthetic HCs and CHCs from virgin queen postpharyngeal glands that are potentially used in close range mate recognition. Olfactometer bioassays of male ants to 15 non-HCs correlated sensory responsiveness to the respective behavioral responses. Comparing olfactory responses between H. saltator males and females, we found that sensilla coeloconica and basiconica of workers showed greater responses and broader selectivity to all compounds. The rarity of CHC-responding trichoid sensilla in Harpegnathos males suggests a more specific role in sexual communication compared to that in females, which use CHCs in a broader communication context.

Olfactory Responses of Southern House Mosquito, Culex quinquefasciatus, to Human Odorants.

Mosquito control is essential to protect humans from mosquito-borne diseases. The host recognition between mosquitoes and humans is achieved by the mosquito olfactory system. Antennal sensilla, which house olfactory receptor neurons, are responsible for detecting chemical cues from hosts. To deepen our understanding of the mechanisms involved in the host seeking behavior of mosquitoes, we conducted an electrophysiological study to investigate the response profile of each type of antennal sensilla to human odorants using single sensillum recording. In this study, more than 100 human odorants have been applied as stimuli to 5 morphological types of sensilla, long sharp trichoid (LST), short sharp trichoid (SST), short blunt trichoid I (SBTI), short blunt trichoid II (SBTII), and grooved peg (GP). Different types of sensilla present distinctive response profiles to the human odorants tested. In particular, SST, SBTI, and SBTII sensilla responded to more than 1 category of human odorants, while GP and LST were narrowly tuned to amines and methyl nonanoate, respectively. The dose-dependent patterns and odorant-specific/chemical structure-specific temporal dynamics of SBTI and SBTII antennal sensilla to human odorants had been further detected. Taken together, our study provides the new information on the olfactory physiology of Culex quinquefasciatus (Diptera: Culicidae) to human odorants, leading to a better understanding of mosquito-host recognition and being important for future development of new reagents in the mosquito control.

Antennal Sensilla and Sexual Dimorphism of the Parasitoid Trichospilus pupivorus (Hymenoptera: Eulophidae).

Sensory structures (sensilla) of insects are present in high number in the antennae are important for perceiving environmental cues. Thus, sensilla play an important role in the localization, discrimination, and acceptance of a possible host by parasitoid insects. The sensilla, classified according to their shape, size, and distribution, may also show sexual dimorphism in insects. The types and distribution of antennal sensilla in female and male parasitoid Trichospilus pupivorus (Ferriere, 1930) (Hymenoptera: Eulophidae) were evaluated. T. pupivorus females had longer antennae than males. Both males and females have ten sensilla types with higher abundance of placoid sensilla in females, which suggest a possible functional dimorphism.

Morphology, Ultrastructure and Possible Functions of Antennal Sensilla of Sitodiplosis mosellana Géhin (Diptera: Cecidomyiidae).

To better understand the olfactory receptive mechanisms involved in host selection and courtship behavior of Sitodiplosis mosellana (Diptera: Cecidomyiidae), one of the most important pests of wheat, scanning and transmission electron microscopy were used to examine the external morphology and ultrastructure of the antennal sensilla. The moniliform antennae exhibit obvious sexual dimorphism: antennae of the males are markedly longer than those of the females. Furthermore, each male flagellomere consists of two globular nodes, whereas each female flagellomere is cylindrical. Seven types of sensilla were identified in both sexes. Two types of s. chaetica have a lumen without dendrites and thick walls, suggesting that they are mechanoreceptors. S. trichodea and s. circumfila are typical chemoreceptors, possessing thin multiporous walls encircling a lumen with multiple dendrites. There are significantly more s. trichodea in female than in male, which may be related to host plant localization. In contrast, male s. circumfila are highly elongated compared to those of females, perhaps for pheromone detection. Peg-shaped s. coeloconica are innervated with unbranched dendrites extending from the base to the distal tip. Type 1 s. coeloconica, which have deep longitudinal grooves and finger-like projections on the surface, may serve as olfactory or humidity receptors, whereas type 2 s. coeloconica, smooth with a terminal pore, may be contact chemoreceptors. Also, this is the first report of Böhm' bristles at proximal scape on antennae of Cecidomyiid species potentially functioning as mechanoreceptors.

Antennal sensilla in the parasitoid Sclerodermus sp. (Hymenoptera: Bethylidae).

Parasitoid wasps of the genus Sclerodermus (Hymenoptera: Bethylidae) are an important natural enemy of the Japanese pine sawyer beetle Monochamus alternatus Hope (Coleoptera: Cerambycidae). In this study, we used scanning electron microscopy to examine the external morphology of the antennal sensilla of Sclerodermus sp. Antennae of females and males comprised the scape, pedicel, and 11 flagellomere segments. Based on the morphology of the sensilla in each sex, seven types of sensillum were identified: sensilla trichodea (Tr.1, Tr.2 and Tr.3), sensilla basiconica (Ba.1, Ba.2, and Ba.3), sensilla styloconica (St.1 and St.2), sensilla placodea, sensilla coeloconica, sensilla squamiforma, and Bohm's bristles. Tr.2, Ba.1, and St.1 were only found in females, whereas Ba.2, Ba.3, and St.2 were only observed in males. Sensilla placodea were the most common, given that they occur on the antennae of many parasitoid Hymenoptera, whereas sensilla Tr were the most abundant, being distributed over the entire antennal surface. These sensilla are likely to have roles in the host locating and habitat searching behavior of adult Sclerodermus wasps. Therefore, our findings provide a basis for further studies of the host location behavior of this and other species of parasitic wasp.

Differential effects of ambient temperature on warm cell responses to infrared radiation in the bloodsucking bug Rhodnius prolixus.

Thermoreceptors provide animals with background information about the thermal environment, which is at least indirectly a prerequisite for thermoregulation and assists bloodsucking insects in the search for their host. Recordings from peg-in-pit sensilla and tapered hairs on the antennae of the bug Rhodnius prolixus revealed two physiologically different types of warm cells. Both types responded more strongly to temperature pulses produced by switching between two air streams at different constant temperatures than to infrared radiation pulses employed in still air. In addition, both warm cells were better able to discriminate small changes in air temperature than in infrared radiation. As convective and radiant heat determines the discharge, it is impossible for a single warm cell to signal the nature of the stimulus unequivocally. Individual responses are ambiguous, not with regard to temperature change, but with regard to its source. We argue that the bugs use mechanical flow information to differentiate between pulses of convective and radiant heat. However, if pulses of radiant heat occur together with a constant temperature air stream, the mechanical cues would not allow avoiding ambiguity that convective heat introduces into radiant heat stimulation. In this situation, the warm cell in the tapered hairs produced stronger responses than those in the peg-in-pit sensilla. The reversal in the excitability of the two types of warm cells provides a criterion by which to distinguish the combination of convective and radiant heat from the stimuli presented alone.

Comparative SEM Study of Sensilla and Tyloid Structures in the Antennae of Vespinae (Hymenoptera: Vespidae).

This study investigates the distribution, morphology, and potential functions of antennal sensilla in various wasp species, including Dolichovespula flora, D. intermedia, Vespula structor, Vl. vulgaris, Provespa barthelemyi, Vespa bicolor, V. ducalis, V. mocsaryana, and V. velutina var. nigothorax. The study thoroughly analyzes the antennal structure of these species, representing all four genera of the yellow-jacket and hornet subfamily Vespinae. Using scanning electron microscopy (SEM), the study identifies a total of nineteen types of sensilla, including sensilla trichodea (ST-I, ST-II, ST-III), sensilla campaniform (SCF-I, SCF-II, SCF-III), pit organs (SCO-I, SCO-II, and SA), sensilla placodea (SP-I, SP-II), sensilla chaetica (SCH-I, SCH-II), sensilla basiconica (SB-I, SB-II), sensilla agmon (SAG-I, SAG-II), and sensilla coelocapitular (SCA). Additionally, tyloids were observed in the males of seven species, except for Vl. structor and Vl. vulgaris. The study provides insights into these sensilla types' morphology, abundance, and distribution. It discusses the variations in sensilla morphology among different species and the presence of gender-specific sensilla. This study provides new data about the morphology and distribution patterns of sensilla and tyloid.

Ultrastructure and distribution of antennal sensilla of parasitic wasp, Cotesia gregalis (Hymenoptera: Braconidae).

Cotesia gregalis Yang et Wei (Hymenoptera: Braconidae) is a gregarious koinobiont endoparasitic wasp attacking the larvae of fall webworm, Hyphantria cunea, an important invasive insect pest in China. To better understand the parasitic wasps' mating and parasitic behaviors, we examined the morphology of the antennae of adult C. gregalis, as well as the type, number, and distribution of antennal sensilla, via scanning electron microscopy. The antennae of female and male C. gregalis are filiform and comprise a scape, pedicel, and 16 flagellomeres. The female antennae are significantly shorter than those of male. A total of nine morphological types of antennal sensilla (mechanoreceptor and chemoreceptor) are presented in both sexes, including four mechanoreceptors (sensilla chaetica [two subtypes], sensilla trichodea and Böhm bristles); five chemoreceptors (sensilla basiconica [two subtypes], sensilla placodea, sensilla styloconica, and sensilla coelocapitula). There is no difference in the type and distribution of antennal sensilla between males and females, but the number and length of some antennal sensilla show sexual dimorphism. The functional morphology of the sensilla of C. gregalis is discussed by comparison with other parasitic wasps. These findings provide foundation for further research on the chemical communication and host localization mechanisms of C. gregalis. RESEARCH HIGHLIGHTS: The first report of morphology and distribution pattern of the antennal sensilla in C. gregalis is discussed. A total of seven main types and nine antennal sensilla subtypes are observed in male and female C. gregalis. The type and distribution of antennal sensilla in males and females are identical; however, the number and length of certain antennal sensilla show sexual dimorphism.

Morphological characterization and distribution of antennal sensilla of Spodoptera frugiperda (Lepidoptera: Noctuidae) using scanning electron microscopy.

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a globally significant agricultural pest, causing severe damage to corn production in China. Chemical odor-based trapping is a major approach for FAW control, making it essential to understand the FAW antennal sensillum types to enhance development of effective chemical odor attractants. In this study, we comprehensively examined the antennal sensilla types of FAW, identifying eight types and two subtypes, including Böhm's bristles, sensilla trichoidea, sensilla chaetica (I and II), sensilla coeloconica, sensilla styloconica, sensilla squamiformia (I and II), sensilla auricillica, and sensilla basiconica. Sensilla chaetica II, and sensilla squamiformia II are reported for the first time for FAW in this study. Detailed low-voltage field emission scanning electron microscope (LVSEM) images and descriptions are provided for each sensillum type. This study provides the morphological information to aid in conducting antennal sensillum neurophysiological tests on FAW. RESEARCH HIGHLIGHTS: The types of sensilla of fall armyworm were examined, identifying eight types and two subtypes, including Böhm's bristles, sensilla trichoidea, sensilla chaetica (I and II), sensilla coeloconica, sensilla styloconica, sensilla squamiformia (I and II), sensilla auricillica, and sensilla basiconica. Detailed low-voltage field emission scanning electron microscope images and descriptions were provided for each sensillum type.

Antennal excision reveals disparate olfactory expression patterns within castes in Reticulitermes aculabialis (Isoptera: Rhinotermitidae).

In lower termites, which exhibit a high degree of compound eye degradation or absence, antennae play a pivotal role in information acquisition. This comprehensive study investigates the olfactory system of Reticulitermes aculabialis, spanning five developmental stages and three castes. Initially, we characterize the structures and distribution of antennal sensilla across different developmental stages. Results demonstrate variations in sensilla types and distributions among stages, aligning with caste-specific division of labor and suggesting their involvement in environmental sensitivity detection, signal differentiation, and nestmate recognition. Subsequently, we explore the impact of antennal excision on olfactory gene expression in various caste categories through transcriptomics, homology analysis, and expression profiling. Findings reveal that olfactory genes expression is influenced by antennal excision, with outcomes varying according to caste and the extent of excision. Finally, utilizing fluorescence in situ hybridization, we precisely localize the expression sites of olfactory genes within the antennae. This research reveals the intricate and adaptable nature of the termite olfactory system, highlighting its significance in adapting to diverse ecological roles and demands of social living.

Pupal and Adult Experience Affect Adult Response to Food Odour Components in the Flower-Visiting Butterfly Tirumala limniace.

Butterflies have the ability to learn to associate olfactory information with abundant food sources during foraging. How the co-occurrence of both food and food odours affects the learning behaviour of adults and whether butterflies perceive the odour of their surroundings and develop a preference for that odour during the pupal stage have rarely been tested. We examined the effect of experience with food odour components (α-pinene and ethyl acetate) during the pupal and adult stages on the foraging behaviour of the flower-visiting butterfly Tirumala limniace. We found that α-pinene exposure during the pupal stage changed the foraging preference of newly emerged adults. T. limniace exhibits olfactory learning in the adult stage, and adult learning may influence their previous pupal memory. Moreover, adults' odour preference did not continue to increase over multiple training times. The learning ability of adults for floral odours (α-pinene) was greater than that for non-floral odours (ethyl acetate). In contrast to previous studies, we found that males learned odours more efficiently than females did. This could be attributed to differences in antennal sensilla, affecting sensitivity to compounds and nectar demand between males and females. Our study provides further insight into how olfactory learning helps flower-visiting butterflies use food odours to forage better.

Scanning electron microscopy study of the antennal sensilla of cob borer, Stenachroia elongella (Lepidoptera: Pyralidae).

Stenachroia elongella is an important pest of maize in Meghalaya, India. To understand the roles of sensory organs in the biological behaviors of this insect, we determined the structure and distribution of sensilla found on the antenna of both male and female S. elongella by scanning electron microscope. The antenna of both sexes is a filiform type, and the overall length of the female antenna is significantly longer than the male antenna. In both sexes, seven types and two subtypes of antennal sensilla are identified; sensilla trichodea, sensilla chaetica, sensilla styloconica, sensilla coeloconica, sensilla auricillica (I, II), sensilla squamiformia and Böhm sensilla. No sexual dimorphism on the specific occurrence of sensilla is observed. Probable functions are discussed based on their external morphology. These results would be helpful for further studies on TEM investigations, electrophysiological recordings, and behavioral studies. RESEARCH HIGHLIGHTS: Seven types and two subtypes of antennal sensilla were observed in both male and female Stenachroia elongella. Morphology and distribution of the antennal sensilla were discussed. Sexual dimorphism was observed on the overall length of the antenna where the female antenna is longer than the male antenna. No sexual dimorphism was observed on specific occurrences of antennal sensilla.

Comparison of Morphological Characteristics of Antennae and Antennal Sensilla among Four Species of Bumblebees (Hymenoptera: Apidae).

Bumblebees, as pollinators, play an important role in maintaining natural and agricultural ecosystems. Antennae with sensilla of bumblebees as social insects have essential effects in foraging, nest searching, courting, and mating, and are different in species and sexes. Previous studies on the morphology of antennae and sensilla in bumblebees have been limited to a few species and a single caste. To better understand how bumblebees detect and receive the chemical signal from nectariferous plants and foraging behavior, the morphology of antennae with sensilla, including the antennal length, and type, distribution, and number of antennal sensilla in four species, Bombus atripes, Bombus breviceps, Bombus flavescens, and Bombus terrestris was compared by scanning electron microscopy (SEM) herein. The total antennal length of queens are the longest and workers are the shortest in three castes, and in four species the longest of the total antennal length among three castes all are in B. flavescens, which is significantly longer than other species (p < 0.05) and the length of the scape in queens and workers are both longer than males, significantly different in queens (p < 0.05), and not significantly different in workers (p > 0.05), and the length of flagellums in females are not always shorter than males, of which the length of flagellms in queens of B. flavescens are significantly longer than males (p < 0.05), and the length of pedicel and all flagellomeres varies among species and castes. A total of 13 major types of sensilla in total were observed, including trichodea sensilla (TS A-E), placodea sensilla (PS A-B), basiconica sensilla (BaS), coeloconica sensilla (COS A-B), chaetic sensilla (CS A-B), and Böhm sensilla (BS), of which chaetic sensilla B (CS B), only observed in females of B. atripes, was firstly reported in Apidae. Moreover, the number of all sensilla was the most in males, the least was in workers, the number of sensilla varies within castes and species. Furthermore, the morphological characteristics of antennae and the potential functions of sensilla are discussed.

Secondary Rhinaria Contribute to Major Sexual Dimorphism of Antennae in the Aphid Semiaphis heraclei (Takahashi).

Sexual generation is an important generation in the life cycle of host-alternating aphids, and its population size determines the intensity of the peak in the next spring. Although male trapping techniques based on olfactory stimuli have been successfully established in the field, the biological basis of olfactory perception in males is unclear. In this study, we compared the morphology of antennae and the types, sizes, numbers, and distribution of sensilla between males and sexual females in the host-alternating aphid Semiaphis heraclei (Hemiptera: Aphididae). We found that flagellum length differentiation contributed to the majority of the sexual dimorphism of antennae. Most sensillum types or subtypes, including trichoid sensilla subtype I, campaniform sensilla, and primary rhinaria subtypes I and II, were enlarged in males. In addition, males bore more trichoid sensilla subtype I than sexual females. In particular, secondary rhinaria were present in males only and could not be detected in sexual females. These results revealed the structural basis of male olfactory perception. Our findings provide insight into the mechanism underlying chemical communication between sexual aphids and could thus be useful for pest control.

Morphology and ultrastructure of antennal sensilla of the parasitic wasp Baryscapus dioryctriae (Hymenoptera: Eulophidae).

Baryscapus dioryctriae is an endoparasitic wasp in the pupae of many Pyralidae pests, such as Dioryctria mendacella, Ostrinia furnacalis, and Chilo suppressalis. To provide requisite background for our ongoing research on the mechanisms of host location in B. dioryctriae, the morphology, abundance, distribution, and ultrastructure of the antennal sensilla were investigated using scanning and transmission electron microscopy. The geniculate antennae of B. dioryctriae are composed of scape, pedicel, and flagellum. Eight types of sensilla including Böhm sensilla, chaetica, trichodea, basiconic capitate peg, campaniformia, placodea, coeloconica, and sensilla styloconicum with a long hair were identified on both sexes. Sexual dimorphism exists in the antennae of B. dioryctriae. The number of flagellomere in males is over females, and the subtypes and abundance of sensilla are also different between the sexes. Additionally, the possible functions of distinct sensilla were discussed, which varies from olfaction, contact chemoreceptive, mechanoreception to hygro-/thermoreception, especially, the sensilla trichodea and placodea might be involved in olfactory perception in B. dioryctriae. These results provide an essential basis for further study on chemical communication between B. dioryctriae and their hosts, and contribute to the development of B. dioryctriae becoming an effective biocontrol agent against the pests of agriculture and forestry.