Asymmetrical distribution of antennal sensilla in the female Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae)

Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae) is an important egg parasitoid of several major insect pests. To better understand its host finding mechanisms, the antennal sensilla of female wasp were investigated by scanning electron microscopy. Sensilla chaetica were found mainly on radicle and pedicel segments of the antennae. i-Type sensilla, s. campaniformia, and corneous sensilla were detected on the leeward side, while s. coeloconica and lance sensilla were presented on the windward side of the antennae. S. trichodea and s. basiconica were more abundant on the leeward side than on the windward side of the antennae. More s. placodea were found on the windward side than on the leeward side of the right antenna, while the opposite results were observed on the left antenna. Overall, more s. placodea were found on the right antenna than that on the left antenna. The numbers of s. trichodea and s. basiconica on the clava or the third flagellum antennomere of the right antenna were more than those of the left antenna, whereas their distribution patterns on the other corresponding antennomeres were reverse. Our results showed that there is a strong asymmetrical antennal sensilla distribution quantitatively and spatially between the left and right antennae. Placoid sensilla are present more on the right antenna than on the left antenna. S. campaniformia, corneous sensilla, and i-type sensilla were found only on the leeward side of the antennal clava, while their external morphology and potential functions were described and discussed in detail for the first time.     

Morphology and distribution of antennal sensilla in a parasitoid fly,Gymnosoma rotundatum (Diptera: Tachinidae)

Morphology of antennal sensilla and their distribution were investigated in male and female adults of the parasitoid fly Gymnosoma rotundatum (Diptera: Tachinidae) using scanning electron microscopy (SEM). The overall length and shape were not different between males and females from each other. Three basic types of sensilla (sensilla basiconica, s. chaetica, and s. coeloconica) were identified from both sexes, but with variations in numbers and distribution along the antennae. The s. basiconica and s. chaetica could be divided further into subtypes; s. basiconica into three subtypes and s. chaetica into two subtypes. All the basiconica subtypes 1, 2, and 3 were multiporous, indicating that their primary function was olfactory. The sensilla basiconica was most abundant on the antennae of both sexes. The abundance of s. basiconica subtype 1 was different, but other subtypes 2 and 3 were similar between males and females. There was no pore on the cuticular surface of the s. chaetica and s. coeloconica, suggesting that they are likely to be a mechanosensory or a thermohygroreceptory function. The abundance of the two sensillum types was similar between males and females. The morphological information obtained in our study provides a basis for future investigations into the sensory physiological function, and associated behaviors, of each type of sensilla in this parasitoid fly.     

Morphology and distribution of antennal sensilla in egg parasitoid,Ooencyrtus nezarae (Hymenoptera: Encyrtidae)

Morphology of antennal sensilla and their distribution were investigated in adults of Ooencyrtus nezarae, an egg parasitoid of Riptortus pedestris, using scanning electron microscopy. Male antennae was found to be significantly greater in overall length than female antennae. The antenna of O. nezarae was composed of the radicula, scape, pedicel, funicle and clava in both sexes, with seven types of sensilla identified: sensillum trichodea; s. finger‐like; s. placoidea; s. chaetica; s. basiconica; s. coeloconica, and s. campaniform. They occur in varying number and distribution along the antennae. Two sensillum types were further categorized into additional subtypes, with two subtypes in s. trichodea and three in s. chaetica. Among all characterized sensilla, s. trichodea subtype 1 and s. placoidea were multiporous, indicating that the primary function of these sensilla is olfactory. Sensillum trichodea was the most abundant sensillum type on the antennae of both sexes. Sexual dimorphism was only observed from the subtype 1 sensilla of s. trichodea in males and the subtype 3 sensilla of s. chaetica in females. The morphological information established in our study may provide useful information for further investigations in sensory physiological function of each morphological type of sensilla and their related behavior in this egg parasitoid.     

Structure and distribution of antennal sensilla in Pseudosymmachia flavescens (Brenske) (Coleoptera: Scarabaeidae: Melolonthinae)

Morphology, microstructure, and distribution of antennal sensilla were compared between female and male Pseudosymmachia flavescens (Brenske) (Coleoptera: Scarabaeidae: Melolonthinae). Lamellate antennae of P. flavescens were shown to have typical scape, pedicel, and flagellum segments. The flagellum consists of a four-segmented funicle and a three-segmented club. The lengths of their pedicel and funicle were found to be similar in females and males. Distinct sexual differences were observed in the length of lamellar segments. Nine types/subtypes of sensilla were identified on the antennae of both sexes, including Böhm sensilla, sensilla trichodea, sensilla basiconica (SB), and two subtypes for sensilla chaetica, sensilla coeloconica, and sensilla placodea each. Olfactory sensilla (e.g., SB and placodea) are mainly located on three lamellar segments of the antennal club. Variation was also seen in abundance of various types of antennal sensilla, with males possessing significantly more sensilla than females. Sensilla placodea were the most abundant, and their number in males was twice of that in females, showing a clear sexual dimorphism. The difference in the distribution of sensilla placodea might reflect their roles in sexual chemical communication.     

Scanning electron microscopy studies of antennal sensilla of Ooencyrtus phongi (Hymenoptera: Encyrtidae)

Ooencyrtus phongi (Hymenoptera: Encyrtidae) is an important egg parasitoid of the litchi stink bug, Tessaratoma papillosa (Drury) (Hemiptera: Tessaratomidae). Antennae of parasitic Hymenoptera are important sensory organs and play an important role in host location, host discrimination, courtship, and mating behavior. In this article, we examined the external morphology of the antennal sensilla of female and male of O. phongi using scanning electron microscopy. Twelve morphological sensillar types were recognized in both sexes, including the placoid sensilla, basiconic sensilla, two types of sensilla trichodea, and eight types of sensilla chaetica. Major differences were found between the sexes, in number, distribution, shape, structure, and size of the identified sensilla. These results are discussed in relation to the possible role of these sensilla in the host location behavior of O. phongi.     

Morphology and distribution of antennal sensilla of two tortricid moths,Cydia pomonella and C. succedana (Lepidoptera)

Morphology of antennal sensilla and their distributions were investigated in male and female adults of two tortricid moths, Cydia pomonella and C. succedana using scanning electron microscopy. The antennae of both sexes of the two species were filiform, and the overall lengths of the antennae and the number of consisting segments were greater in males than in females. Six types of sensilla (s.) were identified from the antennae of both sexes in the two species: s. trichodea, s. basiconica, s. coeloconica, s. auricillica, s. chaetica, and s. styloconica, in varying numbers and distribution along the antennae. Among them, surface of four sensilla types (s. trichodea, s. basiconica, s. coeloconica, s. auricillica) were multiporous in the two species, indicating that the primary function of these sensilla is olfactory. The s. trichodea were the most numerous on the antennae in both sexes of the two species. Male C. pomonella has a greater number of s. trichodea than the female. The four sensilla types were further divided into different subtypes in the two species; s. trichodea into three subtypes, s. basiconica into two subtypes, s. coeloconica into two subtypes in C. pomonella and one subtype in C. succedana, and s. auricillica into two subtypes. Sexual dimorphism was observed in the subtypes of s. trichodea. The long subtype of s. trichodea occurs only on male antennae, whereas the short subtypes mainly on female antennae. These findings would be helpful for further studies on detailed chemo‐receptive functions of each subtype of the antennal sensilla.     

Distribution and ultrastructure of the antennal sensilla of the grape weevil Naupactus xanthographus (Coleoptera: Curculionidae)

The grape weevil, Naupactus xanthographus Germar (Coleoptera: Curculionidae), is a polyphagous insect native to southern South America that causes considerable damage in grape and other fruit species. In this study, the morphology and ultrastructure of the antennae and the antennal sensilla of N. xanthographus were investigated using scanning electron microscopy and transmission electron microscopy. The antennae consist of a scape, a pedicel, a funicle, and a zone called the “club,” which are all formed by a total of 12 antennomers. Different types of sensilla were observed: sensilla trichoidea, sensilla chaetica type 1 and 2, sensilla basiconica, and sensilla rod‐like. No sexual dimorphism was observed. The possible functions of the sensilla are discussed in relation to their morphology and ultrastructure.     

Scanning electron microscopy of antennal sensible of Anoplistes halodendri halodendri and Anoplistes halodendri ephippium (Coleoptera: Cerambycidae)

Anoplistes halodendri halodendri (Pallas, 1776) and Anoplistes halodendri ephippium (Stevens and Dalman, 1817) are two subspecies of the longicorn beetle A. halodendri (Coleoptera, Cerambycidae). In the recent years, these subspecies have been spreading rapidly in Hippophae rhamnoides and Hedysarum scoparium shrubberies in the Chinese provinces of Shanxi and Kingie, causing mass mortality of these shrubberies species and consequently leading to great damage to local ecological environment construction as well as high economic, ecological, and societal losses. To control their hazards effectively, here, we study and compare the types, densities, and distribution of antennal sensilla of A. h. halodendri and A. h. ephippium using scanning electron microscopy. Eight sensilla types were observed on the antennae of these two subspecies, including placoid sensilla (Ps), chaetica sensilla (ch) (types I-III), sensilla basiconica (b) (types I and II), sensilla gemmiformium (G), and auricillica sensilla (au). Ps predominated on the antennae of both A. h. halodendri and A. h. ephippium, followed by b and ch, and G and au. There were differences between the subspecies in the distribution and density of the different sensilla types, with ch I being found exclusively on the antennae of A. h. ephippium and b I and au on the antennae of A. h. halodendri only. With the exception of Ps, the densities of ch II, ch III, b II, and G on the antennae of A. h. halodendri were much higher than on the antennae of A. h. ephippium. These results provide sufficient evidence to clarify the receptive mechanisms used by these two subspecies of longicorn beetles and their responses to volatile semiochemicals released by their host plants as well as discuss their differences with respect to host and habitat selection.     

Morphology,distribution, and abundance of antennal sensilla of male and female macropterous and brachypterous small brown planthopper,Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae)

The antennal sensilla of both genders of macropterous and brachypterous adults of the small brown planthopper, Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae) were examined using light and scanning electron microscopy. Scanning electron microscopy revealed seven types of antennal sensilla in adult L. striatellus which were not evenly distributed on all antennal segments. Sensilla chaetica, a sensillum campaniformium and a Böhm bristle were found on the scape. Sensilla chaetica, sensilla trichodea, sensilla placodea which always present as plaque organs, sensilla basiconica and a sensillum campaniformium were present on the pedicel. Three sensilla basiconica and one sensillum coeloconicum containing two sensory pegs were located on the swollen sensory region of the basal flagellum. Pores observed on the surface of s. trichodea and s. placodea suggest these organs probably play a role in olfaction, whereas the aporous s. chaetica with flexible sockets probably function as mechanoreceptors. The aporous s. basiconica with inflexible sockets are probable to be thermo‐hygroreceptors while the Böhm bristle and s. campaniformia may act as antennal proprioceptors. The function of s. coeloconicum remains uncertain. The numerical dominance of antennal olfactory receptors suggests olfaction is an important function of the antenna in L. striatellus. Although a small degree of sexual/wing dimorphism was observed in the numbers of sensilla and in the length and width of antennae and antennal segments, the basic shape and structure of the antennae and antennal sensilla did not differ between the gender or wing form in L. striatellus. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

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.     

Antennal sensilla of Eucryptorrhynchus chinensis (Olivier) and Eucryptorrhynchus brandti (Harold) (Coleoptera: Curculionidae)

Eucryptorrhynchus chinensis (Olivier) (Coleoptera: Curculionidae) and E. brandti (Harold) (Coleoptera: Curculionidae) are the two most important pests of tree‐of‐heaven, Ailanthus altissima (Mill.) Swingle and its variety Ailanthus altissima var. Qiantouchun in China. They are also considered potential biological control agents for tree‐of‐heaven in North America. In this study, the external morphologies and antennal sensilla of both species were examined using scanning electron microscopy to better understand their host‐finding mechanisms. Eleven morphological sensilla types were recorded, that is, Böhm bristles, six types of sensilla chaetica (Sch. 1–6), two types of sensilla basiconica (Sb. 1–2), and two types of sensilla trichodea (St. 1–2). Sch. 5 were absent from the antennae of E. chinensis, while Sch. 2 were absent from the antennae of E. brandti. Abundant cuticular pores were present on the antennae of both species. Three types of sensilla on the antennae of E. chinensis that were not found in a previous study, and ten different types of sensilla on the antennae of E. brandti were identified for the first time. The possible functions of the sensilla types are discussed based on a comparison with previous studies. Four types of sensilla (Sb. 1, Sb. 2, St. 2, and Sch. 6) on the antennae of both species indicate chemoreception may play a significant role in host location. Microsc. Res. Tech. 76:968–978, 2013. © 2013 Wiley Periodicals, Inc.     

Observation of antennal sensilla in Xylotrechus grayii (Coleoptera: Cerambycidae) with scanning electron microscopy

The longicorn beetle Xylotrechus grayii (White, 1855) has been spreading rapidly in China, causing mass mortality of honeysuckle which is economically and medicinally important. In order to elucidate the mechanisms of mate and host location and to advance efficient control methods, antennal sensilla features were investigated in both sexes of X. grayii using scanning electron microscopy (SEM). The filiform antennae of both sexes consist of scape, pedicel, and nine flagellomeres (f1–9). Five types of sensilla were observed: sensilla chaetica (5 subtypes, SC1–5), sensilla basiconica (4 subtypes, SB1–4), Böhm bristles (Bm), grooved peg sensilla (Gp), and sensilla campaniformia (Ca). SC were most common on the antennae, followed by SB and Bm. No significant sexual differences in the type, amounts, and distribution of antennal sensilla were found except for the distribution of SB clusters and Ca. SB clusters and Ca occurred on f1–8 of male antennae but were absent on those segments in females, suggesting a potential function as receptors for female sex pheromones. The putative functions of other sensilla are discussed based on their characteristics in related species. This study provides an important foundation for further research on sensory mechanisms and control measures of X. grayii. Microsc. Res. Tech. 77:264–273, 2014. © 2014 Wiley Periodicals, Inc.     

Ultrastructure of antennal sensilla of Erannis ankeraria Staudinger (Lepidoptera: Geometridae)

Erannis ankeraria Staudinger, 1861 (Lepidoptera: Geometridae) is one of the major pests causing serious damages on Larix spp., Quercus L., and Picea Mill. To investigate the conceivable functions of antennal sensilla associated with pheromone detection, we observed the ultrastructure of antennae in female and male of E. ankeraria moths by scanning electron microscopy. Six types (including two subtypes and a new type) of sensilla were recorded and characterized, including Sensilla trichodea (ST I and ST II), Böhm bristles, Sensilla squamiformia, Sensilla chaetica, Sensilla auricillic (SAU) and newly observed serrate‐like sensilla. ST I and SAU were abundant on male antennae, displaying a sexual dismorphism. Serrate‐like sensilla were also peculiar to male antennae. In summary of reported functions of corresponding sensilla, we presumed putative functions of the recorded sensilla in E. ankeraria, providing the morphological basis for sensory mechanisms related to pest management.     

Scanning electron microscopy of sensilla on the labial and maxillary palps of adult Callidiellum villosulum Fairmaire (Coleoptera: Cerambycidae)

This study used scanning electron microscopy (SEM) to observe the morphology and sensilla of the labial and maxillary palps of adult Callidiellum villosulum Fairmaire between sexes. Combining behavioral activities may provide an effective control target for this pest. In this study, the results showed that there were three segments on the labial palps and four segments on the maxillary palps. The length and width of each segment of the labial and maxillary palps were significantly larger in females than in males. Four types of sensilla were found on the labial and maxillary palps of both sexes of adult C. villosulum: sensilla basiconica (SB I, II, III, and IV), sensilla chaetica (SCh I and II), sensilla placodea (SP), and sensilla campaniformia (SCa). SB IV, SCa, and Sh II were significantly more developed on female labial and maxillary palps than on males', which may be related to their oviposition behavior. By contrast, SB I was more significantly developed on males than on females, which may be related to their mating selection. At the same time, for both sexes, the numbers of Sh I and Sh II on the maxillary palps were significantly higher on labial palps. Maxillary palps could be inferred to potentially play a more important role than the labial palps in the activities of adult C. villosulum. Results will help us further understand the host selection and egg-laying behavior of adult C. villosulum. Such an understanding shall greatly promote the information-based design of pest control methods.     

Morphology and distribution of antennal sensilla in adults of Xylotrechus quadripes

Xylotrechus quadripes (Chevrolat) is the serious woodborer pest of arabica coffee (Coffea arabica L.). To further elucidate the behavior mechanism of the insect based on chemical odorant and to advance effective trapping methods, the typology, distribution, and abundance of antennal sensilla were investigated meticulously in both sexes of X. quadripes by scanning electron microscopy. The filiform antennae of both sexes are composed of 11 segments, namely the scape, pedicel, and nine flagellomeres (f1–9). Ten types (14 subtypes) of sensilla were identified morphologically: sensilla chaetica (three subtypes, Ch.1–3), sensilla basiconica (three subtypes, Ba.1–3), Böhm bristles (Bb), sensilla dentiform (De), sensilla trichodea (Tr), sensilla auricillica (Au), sensilla campaniformia (Ca), grooved peg sensilla (Gp), cuticular pores (Cp), and a newly observed sensillum, named sensilla cone (Cone). The sensilla were mainly distributed in flagellomeres, and the types and amounts increased in frequency from scape to the ninth flagellomere. The numbers of sensilla were the highest on the antennal dorsal side, while the lowest on the ventral side. The types of sensilla were the most abundant on the lateral side, and two sensilla basiconica (Ba.1–2) were found exclusively. The average number of Tr, Ba, and Au on the antenna of the males was significantly greater than females, while the Gp and Cp on the antenna of the females were significantly greater than males. Ca was exclusively occurred on the male antennae but was absent in females. This study discusses the putative functions of the antennal sensilla in adults of X. quadripes based on their characteristics in related species' sensilla, and these results provide an important foundation to clarify the ecological adaption, olfactory recognition mechanism, and to develop the chemical ecology control of X. quadripes.     

Sexual dimorphism in antennal morphology and sensilla ultrastructure of a pupal endoparasitoid Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae)

Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae), a pupal parasitoid of a great number of Lepidoptera pests, has a great potential for biological control. To investigate the olfactory system of this parasitoid, we examined the morphology and ultrastructure of the antennal sensilla of both male and female T. howardi using scanning and transmission electron microscopic techniques. Antennae of male and female T. howardi were geniculate in shape, which consisted of scape, pedicel and flagellum with 5 and 4 flagellomeres, respectively. The sexual differences were recorded in the types, structure, distribution and abundance of antennal sensilla of T. howardi. Fourteen morphologically distinct types of antennal sensilla were found on the female antennae, while seventeen on the male antennae. They were: multiporous plate sensilla (MPS1‐4), chaetica sensilla (CH1‐3), multiporous trichodea sensilla (MTS), aporous trichodea sensilla (ATS1‐5), multiporous grooved peg sensilla (MGPS), coeloconic sensilla (COS), campaniform sensilla (CAS), terminal finger‐like hairy sensilla (TFI), cuticular pore (CP), and ventral sensory plaque (VSP). MPS4, ATS (3‐5), and VSP only occurred on the male antennae, while MPS2 and MPS3 only on the female antennae. The MPSs, MTS, MGPS, TFI, and CP may function as olfactory sensilla involving in detecting odor stimuli whereas the ATSs, CHs, and CAS may serve as mechanoreceptors. COS were presumed to play a role as chemo‐, thermo‐ or hygro‐receptor. The results could facilitate future studies on the biology of olfaction in T. howardi. Microsc. Res. Tech. 79:374–384, 2016. © 2016 Wiley Periodicals, Inc.     

Scanning electron microscopy analysis of the cephalic sensilla of Chrysolina aeruginosa Fald. (Coleoptera,Chrysomelidae)

Chrysolina aeruginosa Fald. (Coleoptera, Chrysomelidae) is an important pest of Artemisia ordosica Krasch. In recent years, this phytophagous beetle has spread rapidly throughout northwest China, which has led to mass mortalities of the A. ordosica. This pest has caused great damage to the local ecology. To address this problem, this study compared the sensilla types and their densities on the antennae, maxillary palps, and labial palps of C. aeruginosa. Six different types of sensilla were observed on the antennae using scanning electron microscopy, i.e., sensilla chaetica, sensilla trichodea, sensilla basiconica, sensilla coeloconica, sensilla styloconica, and Böhm bristles. Sensilla chaetica were the main sensilla on the antennae. There was a significant difference in the distribution and density of sensilla trichodea between males and females. Sensilla basiconica were distributed from the fifth to the ninth flagellomeres. Sensilla coeloconica and sensilla styloconica were usually found from the fifth to the eighth flagellomeres. Böhm bristles were found only on the terminal region of the scape and pedicel. Sensilla chaetica and sensilla twig basiconica were observed on the maxillary and labial palps. Sensilla chaetica were distributed all over the maxillary and labial palps. Sensilla twig basiconica were located in the distal areas of these two types of palps. In this study, we also discussed the responses of C. aeruginosa to the volatile semiochemicals produced by their host plants and the behaviours exhibited during host and habitat selection. Microsc. Res. Tech. 76:423–431, 2013. © 2013 Wiley Periodicals, Inc.     

Ultrastructure of sensilla on the maxillary and labial palps of the adult Xylotrechus grayii (Coleoptera: Cerambycidae)

The longhorn beetle, Xylotrechus grayii (White, 1855), is a serious woodborer pest of many economic and medicinal plants. The maxillary and labial palps of X. grayii adults are strongly involved in mating and host selection behaviors. To further develop control strategies of the pest, sensilla on the palps were studied with scanning and transmission electron microscopy. Five types of sensilla (nine subtypes) were identified: sensilla styloconica (four subtypes, Sty1‐4), sensilla chaetica (2 subtypes, SC1‐2), sensilla digitiformia (Di), sensilla basiconica (Ba), and Böhm sensilla (Bm). Sty and Ba have dendrites and wall pores. SC2 has a tubular body. Di exist only on the terminal segment of the maxillary palp. Sty numbers are the highest in both palps, followed by SC. The number of sensilla in the maxillary palp is significantly higher than that in the labial palp. There are no significant sexual differences in sensilla types, characteristics, distribution, and quantity in the maxillary or labial palps, except for the number of SC sensilla on the maxillary palp. Sensilla functions were compared with correlative sensilla in previous studies. Sty may be sense gustation and olfaction stimulation, while SC are mechanoreceptors. Ba are likely thermo‐ and hygroreceptors. The phylliform depression area formed by Di may exert multiple functions. Bm may sense palp position and movement. These results contribute to the study of the electrophysiology and behavior mechanisms of X. grayii.     

Sensory structures on the antenna of soldier and worker castes of the termite species Odontotermes parvidens (Termitidae: Isoptera: Blattaria)

Odontotermes parvidens is a commonly found important pest species of termite that primarily feed on a range of cellulosic sources. In termites, communication among the nestmates is the basis of all their daily activities and the sensory structures present on the sensory appendages play a crucial role in different social behaviors perceiving and processing various signals of the nestmates and external environments. So, it is essential to understand in detail their sensory structures in order to understand the sensory system of the species O. parvidens. Thus, we have studied the antenna which is one of the primary sensory appendages of both soldier and worker individuals of the species to elucidate various antennal sensory structures and their distribution using scanning electron microscopy. Based on the morphological features of various sensilla, we observed seven types of sensilla as sensilla chaetica (subtypes I, II, III, and IV), sensilla trichodea (subtypes I and II), sensilla trichodea curvata (subtypes I and II), sensilla basiconica, sensilla capitula, Böhm bristles, and sensilla campaniformia (subtypes I and II) along with numerous glandular pores on the antenna of soldier and worker castes. We have also discussed the putative functions of all the sensilla observed based on their external morphology and distributional characteristics on the antenna of soldier and worker castes of the species O. parvidens. Furthermore, the abundance of sensillar types on the antenna of both the castes has also been discussed.