Antennal Morphology Research Articles

Sensory Cues Involved in Social Facilitation of Reproduction in Blattella germanica Females

Cockroaches, like many other animal species, form aggregations in which social stimuli from conspecifics can alter the physiology, morphology, or behavior of individuals. In adult females of the German cockroach, Blattella germanica, social isolation slows oocyte development, sexual maturation, and sexual receptivity, whereas social interactions as minimal as between just two females accelerate reproduction; however, the sensory modalities and pathways that mediate these physiological and behavioral changes are poorly understood. We explored the roles of visual, olfactory, and tactile cues in the reproductive physiology of German cockroach females, and whether their effects are species-specific and related to circadian time. Our results show that tactile cues are the primary sensory input associated with social conditions—with no evidence for involvement of the visual and olfactory systems—and that the antennae play an important role in the reception of these tactile cues. This conclusion is supported by the observation that interactions with other insect species of similar or larger size and with similar antennal morphology also stimulate oocyte development in B. germanica. Social facilitation of reproduction is expected to be influenced by the circadian timing system, as females engage in more social contact during the day when they shelter in aggregations with conspecifics. Surprisingly, however, the female's reproductive rate was unresponsive to social interactions during the photophase, whereas social interactions as short as two hours during the scotophase were sufficient to induce faster reproduction.We discuss the adaptive significance of these sensory-neuroendocrine responses in the German cockroach.

Assessment of Patterns of Fluctuating Asymmetry and Sexual Dimorphism in Carabid Body Shape

The measurement tool most used to estimate developmental stability (DS) is fluctuating asymmetry (FA), which is a measure of the small random deviations that occur between the left and right sides of bilaterally symmetrical traits. In the Biobío Region of Chile, forest plantations are a widely extended phenomenon, which affect 27% of the surface area of the region and which are dominated by the monoculture of Pinus radiata. This study evaluated the presence of FA in the body shape of two populations of Ceroglossus chilensis (Eschscholtz) in two 13-year-old forest plantations (commercial thinning) using insects collected with interception traps. Since the biotic and abiotic components of forest plantations are subject to continual anthropic modifications that affect almost all ecological processes, including population dynamics, community composition, and material and energy flows, these characteristics are reflected in the DS of individuals. The results showed that there was greater precision using geometric morphometrics to detect the presence of asymmetry in plantations due to shape analysis, as proposed by studies in antennal morphology using traditional measures. It should be noted that the populations were exposed to different environments; the population in the Coast Range is more humid, while the Andes Foothills population is in a drier area with drier soils. In spite of this, there was minimum phenotypic variation detected at the population level, which reflected the different environments and may be associated with patterns of environmental phenotypic plasticity.

Antennal morphology and sensilla ultrastructure of three tomicus species (coleoptera: Curculionidae, scolytinae)

The antennal morphology and sensilla ultrastructure of Tomicus yunnanensis, T. minor, and T. brevipilosus were studied by scanning electron microscopy and transmission electron microscopy. Eight common sensilla types were recorded: (1) sensilla trichodea (S.tr.) types 1 and 2 were located on the club and were innervated by five and eight dendrites, respectively; (2) sensilla chaetica (S.ch.) types 1 and 2 had no dendrites in the sensilla lymph lumen; (3) sensilla basiconica (S.b.), top-protuberated S.b. and fluted cones (Fl.c.) occurred on the club; and Böhm bristles (B.b.) occurred on the funicle. S.b. were the most abundant and were innervated by 10-14 dendritic branches. Top-protuberated S.b., a new sensilla type, were innervated by one dendrite. Fl.c. were innervated by five dendrites. Only three sensilla furcatea were visible on the antennae of female T. yunnanensis. The possible functions of these sensilla are discussed in relation to their morphology and ultrastructure. No statistical differences between sexes were found in the size and numbers of each sensilla type. Although the three species had similar antennal morphology and sensilla type, sensilla on sub-segments 3 and 4 of the antennal club of T. minor were much sparser than those of T. yunnanensis or T. brevipilosus. Concerning the antennae of T. yunnanensis, there were more S.tr. type 2, S.ch. type 2 and S.b. and the size of S.tr. type 1 and S.b. were significantly greater than those of T. minor.

Western Honeybee Drones and Workers (Apis mellifera ligustica) Have Different Olfactory Mechanisms than Eastern Honeybees (Apis cerana cerana)

The honeybees Apis mellifera ligustica (Aml) and Apis cerana cerana (Acc) are two different western and eastern bee species that evolved in distinct ecologies and developed specific antennal olfactory systems for their survival. Knowledge of how their antennal olfactory systems function in regards to the success of each respective bee species is scarce. We compared the antennal morphology and proteome between respective sexually mature drones and foraging workers of both species using a scanning electron microscope, two-dimensional electrophoresis, mass spectrometry, bioinformatics, and quantitative real-time polymerase chain reaction. Despite the general similarities in antennal morphology of the drone and worker bees between the two species, a total of 106 and 100 proteins altered their expression in the drones' and the workers' antennae, respectively. This suggests that the differences in the olfactory function of each respective bee are supported by the change of their proteome. Of the 106 proteins that altered their expression in the drones, 72 (68%) and 34 (32%) were overexpressed in the drones of Aml and Acc, respectively. The antennae of the Aml drones were built up by the highly expressed proteins that were involved in carbohydrate metabolism and energy production, molecular transporters, antioxidation, and fatty acid metabolism in contrast to the Acc drones. This is believed to enhance the antennal olfactory functions of the Aml drones as compared to the Acc drones during their mating flight. Likewise, of the 100 proteins with expression changes between the worker bees of the two species, 67% were expressed in higher levels in the antennae of Aml worker contrasting to 33% in the Acc worker. The overall higher expressions of proteins related to carbohydrate metabolism and energy production, molecular transporters, and antioxidation in the Aml workers compared with the Acc workers indicate the Aml workers require more antennal proteins for their olfactory mechanisms to perform efficient foraging activities than do the Acc worker bees. These data decipher the mechanisms of the western and eastern drone and worker bees acting in response to their different olfactory system in their distinct ecosystem.

Antennal morphology and sensillar ultrastructure of Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae)

The parasitoid beetle Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae) is an important parasite of longicorn beetles (Cerambycidae), and has been used in China for the biological control of the Asian longicorn beetle and the Japanese pine sawyer. In this study the antennal morphology and sensillar ultrastructure of D. helophoroides were observed using scanning electron microscopy and transmission electron microscopy. Two types of sensilla trichodea (Tr. 1 and Tr. 2), two types of sensilla basiconica (Ba. 1 and Ba. 2), three types of sensilla chaetica (Ch. 1, Ch. 2 and Ch. 3), and Bohm's bristles were identified according to the morphology and fine structure of each type of sensilla in both sexes. Ultrastructural studies revealed porous structures on the cuticle wall and dendritic branches in the inner lumen of Tr. 1, Tr. 2, Ba. 1, and Ba. 2, thereby suggesting chemoreceptor functions. No difference in shape, structure, sensilla distribution and typology was observed between the sexes. These structures likely have roles in the host locating and habitat searching behavior of adult D. helophoroides, and suggest future studies on the olfaction and host location behavior of D. helophoroides and other coleopteran parasitoids.

Pheromone production, male abundance, body size, and the evolution of elaborate antennae in moths.

The males of some species of moths possess elaborate feathery antennae. It is widely assumed that these striking morphological features have evolved through selection for males with greater sensitivity to the female sex pheromone, which is typically released in minute quantities. Accordingly, females of species in which males have elaborate (i.e., pectinate, bipectinate, or quadripectinate) antennae should produce the smallest quantities of pheromone. Alternatively, antennal morphology may be associated with the chemical properties of the pheromone components, with elaborate antennae being associated with pheromones that diffuse more quickly (i.e., have lower molecular weights). Finally, antennal morphology may reflect population structure, with low population abundance selecting for higher sensitivity and hence more elaborate antennae. We conducted a phylogenetic comparative analysis to test these explanations using pheromone chemical data and trapping data for 152 moth species. Elaborate antennae are associated with larger body size (longer forewing length), which suggests a biological cost that smaller moth species cannot bear. Body size is also positively correlated with pheromone titre and negatively correlated with population abundance (estimated by male abundance). Removing the effects of body size revealed no association between the shape of antennae and either pheromone titre, male abundance, or mean molecular weight of the pheromone components. However, among species with elaborate antennae, longer antennae were typically associated with lower male abundances and pheromone compounds with lower molecular weight, suggesting that male distribution and a more rapidly diffusing female sex pheromone may influence the size but not the general shape of male antennae.

Observations on antennal morphology in Diptera, with particular reference to the articular surfaces between segments 2 and 3 in the Cyclorrhapha

The main features of antennal segments 2 and 3 seen in the higher Diptera are described, including many that are not or inadequately covered in available publications. The following terms are introduced or clarified: for segment 2 or the pedicel—annular ridge, caestus, chin, collar, conus, distal articular surface, encircling furrow, foramen of articulation, foraminal cusp, foraminal ring, pedicellar button, pedicellar cup, rim; for segment 3 or the postpedicel—basal foramen, basal hollow, basal stem, postpedicellar pouch, sacculus, scabrous tongue, sub-basal caecum; for the stylus or arista—stylar goblet. Particular attention is given to the occurrence and position of the pedicellar button. The button is the cuticular component of a chordotonal organ, which perhaps has the role of a baroreceptor. It is present in the majority of families of Diptera, and possibly was present in the ancestral dipteran. Some generalizations about antennal structure are made, and a diagram showing the main trends in antennal evolution in the Eremoneura is provided. The general form of the antenna shows a transition from approximate radial symmetry (e.g., in Empis, Microphor, and Opetia) through to superficial bilateral symmetry (in many taxa of Eumuscomorpha), though there is usually much asymmetry in detail. More detailed descriptions and illustrations are given for selected taxa of Cyclorrhapha. The phenomenon of an additional concealed segment-like structure between segments 2 and 3, found among the Chloropidae, Pyrgotidae, etc., and formed from the basally flexible conus, is described. Some antennal features of the Calyptratae suggest a relationship to the Tephritoidea. Critical comments are made with regard to the recently published phylogenetic association of the Ironomyiidae with the Phoridae and the Pallopteridae with the Neurochaetidae. In discussing relationships of some taxa, a few non-antennal features, some needing further study, are mentioned, e.g., variation in separation of abdominal tergites 1 and 2 in the Opetiidae and other lower cyclorrhaphous families; the presence of supplementary claw-like terminal tarsal processes in the Lonchopteridae; the apparent restriction of the presence of barbed macrotrichia to the Phoridae, among lower cyclorrhaphans; variation in structure of the prelabrum in the Pyrgotidae; the microstructure of the facial cuticle in the Syringogastridae as compared with that of other families; the calyptrate-like development of the squama in some tephritoid taxa; variation in the subscutellum in the Conopidae; a feature of the larval posterior spiracles diagnostic for Coelopidae.

The source of chilopod sensory information: External structure and distribution of antennal sensilla in Scutigera coleoptrata (chilopoda, Scutigeromorpha)

The investigation of the antennae of Scutigera coleoptrata (Linnaeus, 1758) by scanning electron microscopy (SEM) revealed the presence of five types of sensilla: sensilla trichodea, beak-like sensilla, cone-shaped sensilla brachyconica on the terminal article, sensory cones at the antennal nodes, and the shaft organ. Alongside the presence and absence of antennal sensillar types, three unique characters were found in the Scutigeromorpha: the presence of long antennae with nodes bearing sensory cones, the presence of a bipartite shaft including the shaft organ, and the presence of beak-like sensilla. Neuroanatomical data showed that the animals' brains are equipped with well-developed primary olfactory and mechanosensory centers, suggesting that the antennae must be equipped with specialized sensilla to perceive chemosensory and mechanosensory cues. With the evidence provided in this article for the Scutigeromorpha, SEM data are available at last on the antennal sensilla for all five chilopod taxa, allowing a comparative discussion of antennal morphology in Chilopoda.

Alarm pheromones and chemical communication in nymphs of the tropical bed bug Cimex hemipterus (Hemiptera: Cimicidae).

The recent resurge of bed bug infestations (Cimex spp.; Cimicidae) and their resistance to commonly used pesticides calls for alternative methods of control. Pheromones play an important role in environmentally sustainable methods for the management of many pest insects and may therefore be applicable for the control of bed bugs. The tropical bed bug, Cimex hemipterus, is a temporary ectoparasite on humans and causes severe discomfort. Compared to the common bed bug, Cimex lectularius, little is known about the chemical signalling and pheromone-based behaviour of the tropical species. Here, we show that the antennal morphology and volatile emission of C. hemipterus closely resembles those of C. lectularius and we test their behavioural responses to conspecific odour emissions. Two major volatiles are emitted by male, female and nymph C. hemipterus under stress, (E)-2-hexenal and (E)-2-octenal. Notably, nymph emissions show contrasting ratios of these compounds to adults and are further characterized by the addition of 4-oxo-(E)-2-hexenal and 4-oxo-(E)-2-octenal. The discovery of this nymph pheromone in C. hemipterus is potentially the cause of a repellent effect observed in the bio-tests, where nymph odours induce a significantly stronger repellent reaction in conspecifics than adult odours. Our results suggest that pheromone-based pest control methods developed for C. lectularius could be applicable to C. hemipterus, with the unique nymph blend showing promising practical properties.

Characterization of olfactory sensilla of Stomoxys calcitrans and electrophysiological responses to odorant compounds associated with hosts and oviposition media

Stable flies, Stomoxys calcitrans L. (Diptera: Muscidae), are economically important biting flies that have caused billions of dollars in losses in the livestock industry. Field monitoring studies have indicated that olfaction plays an important role in host location. To further our understanding of stable fly olfaction, we examined the antennal morphology of adults using scanning electron microscopy techniques. Four major types of sensillum were found and classified as: (a) basiconic sensilla; (b) trichoid sensilla with three subtypes; (c) clavate sensilla, and (d) coeloconic sensilla. No significant differences between male and female flies in abundances (total numbers) of these sensillum types were observed, except for medium-sized trichoid sensilla. The distinctive pore structures found on the surface of basiconic and clavate sensilla suggest their olfactory functions. No wall pores were found in trichoid and coeloconic sensilla, which suggests that these two types of sensillum may function as mechano-receptors. Details of the distributions of different sensillum types located on the funicle of the fly antenna were also recorded. Electroantennogram results indicated significant antennal responses to host-associated compounds. The importance of stable fly olfaction relative to host and host environment seeking is discussed. This research provides valuable new information that will enhance future developments in integrated stable fly management.

Description of the first zoea of Domecia glabra Alcock, 1899 (Crustacea: Brachyura, Domeciidae) and implications for the systematics of the Trapezioidea

Abstract The first zoeal stage of the heterotreme domeciid crab Domecia glabra Alcock, 1899 (Trapezioidea), an obligate symbiont on hard corals, is described for the first time on the basis of laboratory-hatched material from Vanuatu. Its morphology is compared to other known zoeae of the Trapeziidae and Tetraliidae. The first stage zoea bears a remarkable similarity to larvae of the thoracotrematous Pinnotheridae, but the resemblance is superficial as their antennal morphologies are different. The key characters of Domecia ally it most closely with Tetralia in the Trapezioidea and supports molecular studies that they are sister taxa. Unfortunately, the zoeal and DNA studies do not give conclusive evidence with regard to whether the Domeciidae is truly trapezioid.

Species of Heterothrips Hood (Terebrantia: Heterothripidae) from Central America

Heterothripidae is a family with three genera: Lenkothrips De Santis & Sureda, Scutothrips Stannard, and Heterothrips Hood. Lenkothrips contains a single species from South America, Scutothrips contains four species, and Heterothrips has more than 60 species. Heterothrips has not been adequately defined. Some species in this genus are associated with host plants of economic importance. In this paper, three new species are described, two of them associated with flowers in fruit tree crops of the family Myrtaceae and the other with a plant in the family Malpighiaceae used as an ornamental. The new species can be distinguished as follows: Heterothrips lopezae n. sp. has remarkably different sculpturing on the pronotum compared with H. sericatus Hood and H. mimosae Mound & Marullo and antennal segments III-IV are pale in colour. Heterothrips lankesteriensis n. sp. is distinguished by the presence of setose tubercles behind the eyes; this character is present only in one other species, H. pubescens Hood, which is clearly distinguished by the presence of pronotal sculpture and the sculpturing of the metanotum. Heterothrips hondurensis n. sp. has unique antennal morphology and is easily recognized from H. lyoniae Hood by the pedicel with divergent sides and antennal segment IV truncated not rounded as in H. lyoniae. A key to the Central American species of Heterothrips is provided.Key words: Heterothripidae, Myrtaceae, Malpighiaceae, fruit crops, ornamentals.DOI: http://dx.doi.org/10.5377/ceiba.v50i1.195

Resurrection of Dryotomicus Wood and description of two new species from the Amazon River Basin (Coleoptera, Curculionidae, Scolytinae, Phloeotribini)

A cladistic analysis based on 20 morphological characters was conducted for 11 species representing two valid and two synonymized Phloeotribini genera. One hundred-eighty most-parsimonious trees were recovered and the Dryotomicus Wood species were monophyletic in a mostly unresolved strict-consensus tree. The unusual antennal morphology, with the length of the first two funicular segments equal to the last three segments and a scape which is twice the length of the funicle, distinguish Dryotomicus from the other Phloeotribini genera. Hence this genus is resurrected because of monophyly and diagnostic characters. Dryotomicus oenophilis sp. n. and Dryotomicus woodrex sp. n. are described from Guyana and Peru, respectively. In the male specimen of Dryotomicus oenophilis, the frons has one median and two large lateral carinae and in the male specimen of Dryotomicus woodrex, the frons has three smaller median tubercles arranged transversely. Phloeotribus puberulus Chapuis and Phloeotribus tuberculatus (Eggers) were monophyletic with the new Dryotomicus species and thus are transferred to this genus. Keys to the Phloeotribini genera and Dryotomicus species are given.

Morphological Characterization and Distribution of Antennal Sensilla of Six Fruit Flies (Diptera: Tephritidae)

Abstract Fruit flies (Diptera: Tephritidae) are important pests of many fruits and vegetables. In this study, the external morphology, types, and distribution of antennal sensilla in both male and female adults of the six fruit fly species, including Bactrocera tau (Walker), Bactrocera dorsalis (Hendel), Bactrocera cucurbitae (Coquillett), Bactrocera minax (Enderlein), Bactrocera diaphora (Hendel), and Bactrocera scutellata (Hendel), were observed by using scanning electron microscopy. The antennae of the six fruit fly species consist of a basal scape, pedicel, and an elongated flagellum. Arising from the proximal dorsal ridge of flagellum there is an arista consisting of two short basal segments and a long thin distal segment. Six distinct morphological types of sensilla are recorded in both sexes, including microtrichial sensilla, sensilla chaetica, sensilla trichoid, sensilla basiconica, short type of sensilla basiconica, and sensilla coeloconica. The abundance and distribution of these six sensilla types on the antennae of both sexes are recorded. In addition, the possible functions of the above-mentioned sensilla types are discussed in light of previously published literature. The functions include the mechanoreception of microtrichial sensilla, sensilla chaetica, and sensilla trichoid; olfactory functions of sensilla basiconic, and sensilla coeloconica; and thermoreception of the short type of sensilla basiconica. Future functional antennal morphology and electrophysiological studies are needed to confirm these proposed functions.

Two new genera and species of chiltoniid amphipods (Crustacea: Amphipoda: Talitroidea) from freshwater mound springs in South Australia

Amphipods within the family Chiltoniidae are an abundant yet taxonomically poorly known member of Australian freshwater habitats. With only four species known from Australia, the group is inadequately defined and marked by taxonomists as difficult to identify. Recent molecular analyses of chiltoniids from mound springs in South Australia detected several distinct species, prompting a morphological revision of material from the central and southern Lake Eyre region. Clear groups defined by unique combinations of morphological characters (focusing on uropodal, coxal, male gnathopod 2, and antennal morphology) were found that closely correlated with clades found in the molecular analyses. Arabunnachiltonia n. gen. is established for A. murphyi n. sp. from Strangways Springs in South Australia. Wangiannachiltonia n. gen. is established for W. guzikae n. sp. from Davenport Springs in South Australia. The chiltoniid genera are discussed and a key is presented to the known Australian species.

New Asian Hydroscapha, with comments on male-female association of co-occuring species (Coleoptera, Myxophaga, Hydroscaphidae)

Four syntopically co-occuring species of the genus Hydroscapha LeConte, 1874 are recorded at three adjacent hygropetric localities in the Indian state of Meghalaya (Khasi Hills). Association of males with conspecific females was recognized as a crucial problem for the taxonomic treatment of these taxa. Antennal morphology and abundance data of all collected morphotypes and their presence/absence at each locality were used for this association; most of these data are, however, shown as insufficient for a reliable association due to intraspecific variability (in the case of antennal morphology) or incomplete knowledge of seasonal dynamics (in the case of relative abundance of males versus females). Utilizing male characters separately from those of females is suggested as a possible solution. Following this approach, updated identification keys for males and females of Asian Hydroscapha and tables summarizing useful diagnostic characters are provided. Disadvantages of this approach are also discussed. The examined samples include two species described as new (Hydroscapha khasiorum sp.n. and H. rajani sp.n.) and H. monticola Löbl, 1994, which is recorded in India for the first time. A fourth species currently represented by one specimen only is left unidentified.

Antennal courtship and functional morphology of tyloids in the parasitoid wasp Syrphoctonus tarsatorius (Hymenoptera: Ichneumonidae: Diplazontinae)

Courtship behaviour and associated morphological characters are believed to evolve under diversifying sexual selection. In Hymenoptera, sexually dimorphic antennal structures, the ‘tyloids’, show a large variability. Although crucial for functional interpretation, the link between tyloid morphology and courtship behaviour has gained only limited attention. Here, we investigate antennal morphology and antennal courtship in the parasitoid wasp Syrphoctonus tarsatorius (Hymenoptera: Ichneumonidae: Diplazontinae). We confirm the glandular nature of the tyloids by light and scanning electron microscopy. Moreover, we report a new form of antennation during courtship, antennal double-coiling, which links morphology and behaviour by bringing the tyloids in direct contact with the antennae of the female, thus probably facilitating the transfer of a contact pheromone. We show that a change in haemolymph pressure is the activator of the antennal movement and that it can be reproduced in the laboratory using amputated antennae. Investigations of antennal structure and movement in three additional hymenopteran species suggest that the number and location of tyloids coincide with the modality of antennal coiling. Our method for simulating antennal movement will enable retrieving information about courtship behaviour from museum specimens, thus leading to a better understanding of the evolution of courtship behaviour in Hymenoptera.

A revision of the mantispid genus Nampista (Neuropterida, Mantispidae)

The poorly known mantispid genus Nampista is revised, which has previously been considered to contain its type species, Nampista auriventris (Guerin-Meneville, 1838), only. The genus is diagnosed and briefly compared with Euclimacia. Two species-group names are newly transferred to Nampista: Euclimacia africana (Esben-Petersen, 1927) and Euclimacia africana ragazziana (Navas, 1929), the latter raised to full species rank. The three species now placed in Nampista are keyed, diagnosed and described. All available information on collecting records and geographic distribution are provided. Digital images of specimens of all species are given. A considerable amount of sexual dimorphism in Nampista is recorded: Both sexes have disc-shaped antennal segments, but they are markedly wider in male Nampista (relative to the rest of the body) than in females. This is the first case of sexual dimorphism in antennal morphology reported in Mantispidae. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Discrimination between two sibling species of Acroperus (Baird, 1843) from the Palearctic (Cladocera: Anomopoda: Chydoridae)

Morphology and differential diagnosis of two common Eurasian but frequently confused Eurasian cladocerans, Acroperus harpae (Baird, 1834) and A. angustatus Sars, 1863, was investigated. Validity of both species is confirmed. A significant intraspecific variation in body shapes, unusual for species of the family Chydoridae, is present in females of both species. This “traditional” character is unreliable as diagnostic feature. Prominent differences between two species are revealed in antennal morphology, used for identification of all instars of males and females. Detailed morphology of males, postembryonal development of both males and females was studied in details for the first time. Our data suggest that two other European Acroperus taxa, A. neglectus Lilljeborg, 1900 and A. alonoides Hudendorff, 1876, are junior synonyms.

Antennal Morphology and Sensilla of Asian Multicolored Ladybird Beetles,Harmonia axyridisPallas (Coleoptera: Coccinellidae)

We investigated the antennal morphology, sensillar types, and sensillar distribution in the dark (“melanic”) and the light (“succinea”) forms of Asian multicolored ladybirds, H. axyridis, using scanning electron microscopy (SEM). Antennae of both sexes of H. axyridis consist of the scape, pedicel, and nine flagellomeres. Seven sensillar types are distinguished: four types of sensilla trichodeae (s.tr), four types of sensilla basiconicae (s.ba), four types of sensilla chaetica, and one type each of sensilla coeloconica (s.co), sensilla sporangium (s.sp), sensilla placoidea (s.pl), and Böhm bristle (s.bm). Sensilla trichodea are the most numerous; sensilla chaetica are the next most abundant. The number of other sensillar types is greatly reduced. On the tip of the 9th flagellomere, various types of sensilla are densely packed, except for s.bm and s.pl. No remarkable differences are found in the antennal size, shape, and sensillar types between the melanic and succinea forms of H. axyridis, but there is a difference in the total number of s.tr.2 between the two forms. No differences are found in the antennal size and the total number of sensillae between males and females of each form. According to the distribution of sensillae and sensillar functions reported in the past, s.tr are presumed to be pheromone receptors in H. axyridis, s.ch may function as mechanoreceptors and chemoreceptors, s.ba and s.co are postulated as plant volatiles receptors and chemo-, thermo-, or hygroreceptions, respectively, and s.bm may be related to perceiving the antennal position and movement.