Anterior alimentary canal of the pear Psylla,Psylla pyricola foerster (Homoptera,Psyllidae)

Scanning and light microscopy investigations of the anterior alimentary canal of the pear psylla, Psylla pyricola Foerster (Homoptera: Psyllidae), revealed the morphology of the labium and stylets, as well as the presence of sensory structures and a valve in the precibarium. The labium consists of three telescoping segments with an internal labial groove, which surrounds and supports the stylet bundle. Also a part of the labial groove is the internal labial clamp. The stylet bundle is comprised of paired styliform mandibles and maxillae, which interlock to form the food and salivary canals. The stylet bundle proximal to the labium forms a large loop within a membranous crumena. When fully retracted the coiled stylets are under tension. Stylet extension generates increasing tension so that when retracted the stylets readily recoil within the crumena. Penetration of leaf tissues by the stylet bundle is dependent on the interaction between stylet muscles, opening and closing of the labial clamp, the barbed stylet tips, and the ventral position of the labium. Proximal to the crumena the paired stylets separate and diverge at the entrance of the precibarium, which is formed by the interlocking of the epi-and hypopharynges. There are 18 sensory structures in the precibarium, as well as a precibarial valve. These structures appear to be homologous to similar structures observed previously in aphids and leafhoppers. The morphology and the location of the precibarial sensilla suggest that, like the precibarial sensory organs of aphids and leafhoppers, they are gustatory and probably mediate acceptance or rejection of plant fluids, thus playing a major role in locating tissues for feeding.     

Distribution of chemo- and mechanoreceptors on the antennae and maxillae of Busseola fusca larvae

The stem borer Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is a major pest of maize, Zea mays L., and sorghum, Sorghum bicolor (L.) Moench (both Poaceae), in sub-Saharan Africa. Like in many other lepidopteran insects, the success of B. fusca in recognizing and colonizing a limited variety of plants is based on the interaction between its sensory systems and the physicochemical characteristics of its immediate environment. The sensilla on the maxillary galeae of B. fusca larvae are typical of Lepidoptera and comprise two uniporous styloconic sensilla, which are contact chemoreceptors, three basiconic sensilla, and two aporous sensilla chaetica. The maxillary palp is two-segmented and has eight small basiconic sensilla at the tip, which were also found to be gustatory. The antennae of B. fusca larvae are short and simple. The sensilla of the antenna are composed of two aporous sensilla chaetica, three multiporous cone-shaped basiconic sensilla, three small basiconic sensilla, and one aporous styloconic sensillum. The basiconic sensillum located on the third antennal segment displayed a contact chemoreception response. The other basiconic sensilla did not show any action potential activity in tip-recording tests. The significant and positive dose–response curve obtained for the antennal basiconic sensillum with sucrose indicated for the first time the presence of gustatory chemoreceptors on the antennae of a lepidopteran larva.     

Oviposition Behaviour of Lygus rugulipennis and its Preferences for Plant Wounds

Little information is available on the oviposition behaviour and strategies of Lygus bugs, and these topics are unknown for most Miridae. Lygus rugulipennis, a widespread polyphagous species in the Palaearctic Region, is a serious pest of both herbaceous crops and fruit trees. Here we report on the L. rugulipennis oviposition behaviour and preferences. Experiments were carried out utilizing fresh green beans, and data were recorded using a computerized system for behavioural acquisitions. The L. rugulipennis female examines the plant substrate by means of the labial tip and then probes into the tissue using her stylets. Once the substrate is suitable, the female inserts her ovipositor precisely in the point previously probed and lays an egg. To investigate females’ oviposition preferences, their behaviour was compared on healthy green beans vs. artificially wounded green beans, with different types of wounds and at different time intervals (1?h, 6?h, 12?h, 24?h and 48?h) after wounding. Through labial and stylet examination, females distinguished healthy and wounded tissues and significantly preferred to oviposit in the latter, with different egg densities depending on the type of wound. Such preference changed at different time intervals after wounding. The lower resistance of the wounded substrate to ovipositor insertion, compared with the healthy substrate, was confirmed through a penetrometer test. Lygus preference for damaged tissues is discussed in terms of oviposition strategies in the insect-plant interaction context and strategies to escape natural enemies.     

Antennal sensilla in five Psychodini moth flies (Diptera: Psychodidae: Psychodinae) pollinators of Arum spp. (Araceae)

The pollination of the genus Arum (Araceae) is mainly achieved by deception, the floral odour mimicking the pollinator ovipositing site. In order to discover the sensory organs involved in this attraction, we have studied the antennae of five species of psychodine moth-flies (former Psychoda sensu lato=Psychodini), pollinators of Arum spp. The antennae of the five Psychodini reveal seven types of sensilla: multiporous tribranched sensilla basiconica (sensilla ascoidea), multiporous sensilla basiconica, multiporous sensilla coeloconica, multiporous sensilla auricillica, uniporous sensilla basiconica, aporous sensilla chaetica, aporous Böhm’s sensilla. Each species possesses three, five or six of these sensillum types. All the multiporous sensilla are probably olfactory receptors while the uniporous sensilla basiconica must possess a contact chemoreceptive function. The multiporous tribranched sensilla basiconica (s. ascoidea), present in all the species, are the best candidates for the reception of the odours given off by the ovipositing sites and the inflorescences of Arum. The multiporous sensilla basiconica and the multiporous sensilla coeloconica may be involved respectively as CO₂ receptors or thermoreceptors. Psychoda phalaenoides, which is the main pollinator of A. maculatum, is the species which possesses the largest number of antennal sensilla. The sexual dimorphism, studied only in Psycha grisescens, as concerns the number of sensilla and the absence of a sensillum type which differ according to sex, is difficult to interpret.     

Contact chemoreception related to host selection and oviposition behaviour in the monarch butterfly, Danaus plexippus

Abstract. Behavioural events during host selection by ovipositing monarch butterflies (Danaus plexippus (L.), Danainae, Nymphalidae) include tapping the leaf surface with fore-tarsi and touching this surface with mid-tarsi (‘drumming’) and antennae. Flavonoids identified from host plant extracts are known to stimulate oviposition. Scanning electron microscopy revealed the presence of contact-chemoreceptor sensilla on all appendages that contact the leaf surface. This electrophysiological study was conducted to identify the contact chemoreceptors that are sensitive to the known oviposition stimuli and are therefore probably involved in host recognition. Receptor cells of conspicuous sensilla grouped in clusters on fore-tarsi of females were sensitive to the behaviourally active butanol fraction of host plant (Asclepias curassavica) extract. However, these receptors generally had low sensitivity to three oviposition-stimulating flavonoids identified from this fraction, but they were also sensitive to the butanol fraction of a non-host (Brassica oleracea). Chemoreceptors in sensilla of the tarsomers 2–4 of the mid-legs also responded to the behaviourally active fraction of host plant extract and showed some sensitivity to two of the flavonoids that stimulate oviposition. Similar results were obtained from receptor cells in sensilla on the tip of the antennae. Most of these sensilla had cells responding to the butanol fraction of A. curassavica extract but only 25% of them were also sensitive to one of the behaviourally active flavonoids. These electrophysiological results, in combination with behavioural observations, suggest that host selection in monarch butterflies relies on a complex pattern of peripheral sensory information from several types of tarsal and antennal contact chemoreceptors.     

Sexual dimorphism of antennal,tarsal and ovipositor chemosensilla in the African stemborer,Busseola fusca (Fuller) (Lepidoptera: Noctuidae)

The number and distribution of chemosensilla located on different organs of Busseola fusca (Fuller) (Lepidoptera: Noctuidae) males and females are described based on observations using scanning electron microscopy, selective staining with silver nitrate, and gustatory electrophysiological recording. The antennae and the fifth tarsomere of the prothoracic legs of both sexes bear chemosensilla: uniporous chaetica and multiporous trichoidea sensilla. However, there is a sexual dimorphism in the number and size of sensilla on these organs. The distal part of the ovipositor has uniporous gustatory chemosensilla of the chaetica type. The involvement of these sensilla in oviposition site selection by B. fusca is discussed.     

Fine structure of the mouthparts of Diostrombus politus and Proutista moesta (Hemiptera: Derbidae)

Insect mouthparts are important sensory and feeding structures, morphological studies of this organ can provide additional data for phylogenetic studies. The planthopper superfamily Fulgoroidea is among the dominant groups of phytophagous insects, however, the mouthparts ultrastructure of this superfamily remains unsatisfactorily studied. This study investigates the ultrastructure of the mouthparts of two species in the family Derbidae (Hemiptera: Fulgoroidea), Diostrombus politus Uhler and Proutista moesta (Westwood), using a scanning electron microscope. The results show that these two derbids are of a typical piercing-sucking type found in Hemiptera. They consist of a cone-shaped labrum, a three-segmented labium and a stylet fascicle with two interlocked maxillary stylets incompletely wrapped by two mandibular stylets. The arrangement of the sensilla on the labial tip differ slightly between the two derbid species, and the subapical labial sensilla are likely different among genera in the family Derbidae.     

Morphology of the mouthparts of the spittlebug Philagra albinotata Uhler (Hemiptera: Cercopoidea: Aphrophoridae)

Mouthparts associated with feeding behavior and feeding habits are important sensory and feeding structures in insects. To obtain a better understanding of feeding in Cercopoidea, the morphology of mouthparts of the spittlebug, Philagra albinotata Uhler was examined using scanning electron microscopy. The mouthparts of P. albinotata are of the typical piercing–sucking type found in Hemiptera, comprising a cone-shaped labrum, a tube-like, three-segmented labium with a deep groove on the anterior side, and a stylet fascicle consisting of two mandibular and two maxillary stylets. The mandibles consist of a dorsal smooth region and a ventral serrate region near the apical half of the external convex region, and bear five nodules or teeth on the dorsal external convex region on the distal extremity; these are regarded as unique features that distinguish spittlebugs from other groups of Hemiptera. The externally smooth maxillary stylets, interlocked to form a larger food canal and a smaller salivary canal, are asymmetrical only in the internal position of longitudinal carinae and grooves. One dendritic canal is found in each maxilla and one in each mandible. Two types of sensilla trichodea, three types of sensilla basiconica and groups of multi-peg structures occur in different locations on the labium, specifically the labial tip with two lateral lobes divided into anterior sensory fields with ten small peg sensilla arranged in a 5 + 4 + 1 pattern and one big peg sensillum, and posterior sensory fields with four sensilla trichodea. Compared with those of previously studied Auchenorrhyncha, the mouthparts of P. albinotata may be distinguished by the shape of the mandibles, the multi-peg structures and a tooth between the salivary canal and the food canal on the extreme end of the stylets. The mouthpart morphology is illustrated using scanning electron micrographs, and the taxonomic and putative functional significance of the different structures is briefly discussed.     

The role of contact chemoreception in the host location process of an egg parasitoid

Taste allows insects to detect palatable or toxic foods, identify a mate, and select appropriate oviposition sites. The gustatory system strongly contributes to the survival and reproductive success of many species, yet it is rarely studied in insect parasitoids. In order to locate and assess a host in which they will lay their eggs, female wasps actively search for chemical cues using their sensory organs present mainly on the antennae. In this paper, we studied the role of antennal taste sensilla chaetica in the perception of contact semiochemicals in Trissolcus brochymenae (Hymenoptera: Platygastridae), an egg parasitoid of the brassicaceae pest Murgantia histrionica (Heteroptera: Pentatomidae). Methanolic extracts obtained from male and female hosts elicited action potentials in taste neurons housed in antennal sensilla chaetica, indicating that these sensilla are involved in the perception of non volatile host kairomones. In behavioural assays, wasp females displayed an intense searching behaviour in open arenas treated with host extracts, thus confirming that these kairomones are soluble in polar solvents. We further investigated the extracts by Gas Chromatography-Mass Spectrometry (GC-MS) and found that they contain several compounds which are good candidates for these contact kairomones. This study contributes to better understanding contact chemoreception in egg parasitoids and identifying gustatory receptor neurons involved in the host location process.     

Fine structure and sensory apparatus of the mouthparts of the pear psyllid,Cacopsylla chinensis (Yang et Li) (Hemiptera: Psyllidae)

The pear psyllid, Cacopsylla chinensis (Yang et Li) (Hemiptera: Psyllidae), is one of the most significant economic pests of pear in China, causing direct damage through feeding by the highly specialized piercing–sucking mouthparts. The ultrastructural morphology and sensory apparatus of the mouthparts of the adult were examined using scanning and transmission electron microscopy. The piercing–sucking mouthparts of C. chinensis are composed of a three-segmented labium with a deep groove in the anterior side, a stylet fascicle consisting of two mandibular and two maxillary stylets, and a pyramid-shaped labrum. Proximal to the labium, the stylet fascicle forms a large loop within a membranous crumena. Mandibles, with more than ten teeth on the external convex region, can be seen on the distal extremity. Smooth maxillary stylets are interlocked to form a larger food canal and a smaller salivary canal. One dendritic canal housing 2 dendrites is also found in each mandible. Two types of sensilla trichodea, four types of sensilla basiconica, single as well as groups of sensilla campaniformia, and oval flattened sensilla occur in different locations on the labium, whereas a kind of sensilla basiconica is at the junction of the labrum and anteclypeus. Sensilla trichodea and sensilla campaniformia, always present with denticles, are present on the middle labial segment. Three types of sensilla basiconica, two types of sensilla trichodea and two oval flattened sensilla are located on the distal labial segment. The mouthpart morphology and abundance of sensilla located on the labium in C. chinensis are illustrated, along with a brief discussion of their taxonomic and putative functional significance.     

Morphology and distribution of the external labial sensilla in Fulgoromorpha (Insecta: Hemiptera)

The present paper describes the sensory structures on the apical segment of the labium in fifteen fulgoromorphan families (Hemiptera: Fulgoromorpha), using the scanning electron microscope. Thirteen morphologically distinct types of sensilla are identified: five types of multiporous sensilla, four types of uniporous sensilla and four types of nonporous sensilla. Three subapical sensory organ types are also recognized, formed from one to several sensilla, each characteristic of a family group. Sensilla chaetica (mechanoreceptive sensilla) fall into three categories dependent on length and are numerous and evenly distributed on the surface of the labium except where they occur on specialized sensory fields. The planthopper morphological ground plan is represented by two apical pair of sensory fields (dorsal and ventral) on which 11 dorsal pairs of sensilla (10 peg-like pairs + 1 specialized pair dome or cupola-like) and 2 ventral pairs of sensilla basiconica occur. Two main patterns (cixiid and issid) together with more specialized ones (derbid, lophopid, flatid and fulgorid) are reported. Disparity and diversity of the sensory structures are analyzed from a taxonomic and functional perspective. A gustatory function is provided for several chemoreceptive labial sensilla, as in the antennal flagellum sensilla in some other Hemiptera. This represents a more recently evolved function for the planthopper labium. Finally, further lines of study are suggested for future work on the phylogeny of the group based on the studied characters.     

Functional bases of host-acceptance behaviour in the aphid parasitoid Aphidius ervi

Abstract.  The host acceptance behaviour in Aphidius ervi is investigated, assessing the role of both external and internal host-associated cues, offered to the experimental parasitoids with parafilm-made aphid dummies. The reaction to internal cues present in the host haemolymph is clearly evident, and its intensity is enhanced by external cues. Parasitoid females lay few eggs in aphid dummies filled with host haemolymph. A significant increase in the number of both oviposition reactions (host stinging) and egg laying is observed only when these dummies are coated with cornicle secretion. However, this enhancement is not observed when the aphid dummies contain distilled water. Thus, the host acceptance behaviour of A. ervi females appears to be controlled by the integration of both external and internal chemical cues. The physiological basis of this behavioural response is investigated with a detailed study on the anatomy and ultrastructure of A. ervi ovipositor. The detection of chemical cues present in the host haemolymph that act as kairomones is made possible by the presence of gustatory sensilla on the tip of the ovipositor. These sensilla consist of porous areas, reached by unbranched dendrites running inside both the lower valves (i.e. first valvulae) and the unpaired upper valve (i.e. second valvulae). The mechanosensory function during oviposition appears to be provided mostly by the basiconic sensilla found on the tip of external valves (i.e. third valvulae). A tentative functional model accounting for the observed oviposition behaviour of A. ervi is proposed.     

Sensilla on antennae,ovipositor and tarsi of the larval parasitoids,Cotesia sesamiae (Cameron 1906) and Cotesia flavipes Cameron 1891 (Hymenoptera: Braconidae): a comparative scanning electron microscopy study

Two braconid parasitoids of cereal stemborers in eastern Africa, Cotesia sesamiae and Cotesia flavipes, have been shown to display a similar hierarchy of behavioural events during host recognition and acceptance. In order to understand the mechanisms underlying host recognition and acceptance, the morphology of antennal sensilla on the last antennomeres, on the ovipositor, and on the fifth tarsomere and pretarsus of the prothoracic legs tarsi were studied using scanning electron microscopy followed by selective silver nitrate staining. It appeared that female C. sesamiae and C. flavipes shared the same types and distribution of sensory receptors, which enable them to detect volatiles and contact chemical stimuli from their hosts. In both parasitoids, four types of sensilla were identified on the three terminal antennomeres: (i) non-porous sensilla trichodea likely to be involved in mechanoreception, (ii) uniporous sensilla chaetica with porous tips that have gustatory functions, (iii) multiporous sensilla placodea, which are likely to have olfactory function, and (iv) sensilla coeloconica known to have thermo-hygroreceptive function. The tarsi of both parasitoids possessed a few uniporous sensilla chaetica with porous tips, which may have gustatory functions. The distal end of the ovipositor bore numerous dome-shaped sensilla. However, there were no sensilla coeloconica or styloconica, known to have gustatory function in other parasitoid species, on the ovipositors of the two braconid wasps.     

Tarsal taste sensilla of the autumn gum moth, Mnesampela privata: morphology and electrophysiological activity

Mnesampela privata Guenée (Lepidoptera: Geometridae: Ennominae) is a native Australian geometrid that conducts considerable host assessment prior to ovipositing on its host plants, which belong to the genus Eucalyptus . The leaves of some of their hosts are covered with a particularly thick and waxy cuticle and we have shown that epicuticular waxes influence the oviposition preferences of females. This necessitates that M. privata has evolved specific chemosensory organs to assess the identity and perhaps even the quality of its hosts. In this work, we examined the morphology of tarsal taste sensilla and the sensitivity of their sensory neurones to a range of primary metabolites possibly influential on host assessment and oviposition. The ventral surface of the fifth tarsomere of females bear two parallel rows of up to eight sensilla, each loosely aligned with two parallel rows of five spines. Salts, sugars, and amino acids elicited phasi-tonic multicellular neuronal responses of variable magnitude and form. Two pairs of sensilla are closely apposed to the most distal spine in each row; the sensory neurones associated with these sensilla exhibited notably larger responses to alanine and serine compared with those of all other sensilla. The arrangement of the taste sensilla in close proximity to prominent tarsal spines is unique and could represent an adaptation that enables them to penetrate the wax layer and be brought into contact with primary metabolites present closer to the leaf surface.     

Oviposition by Lobesia botrana is stimulated by sugars detected by contact chemoreceptors

Abstract.  The influence of glucose, fructose and sucrose on oviposition site selection by Lobesia botrana is studied by combining behavioural and electrophysiological experiments. Oviposition choice assays, using surrogate grapes treated with grape berry surface extracts of Vitis vinifera cv. Merlot at different development stages, show that L. botrana females are most stimulated by extracts of mature berries containing the highest concentrations of glucose and fructose. Choice assays reveal that the oviposition response to these sugars is dose-dependant (with a threshold of the applied solution = 10 m m and a maximum stimulation at 1  m ) and that females are more sensitive to fructose than to glucose. Tarsal contact-chemoreceptor sensilla are unresponsive to stimulation with sugars but the ovipositor sensilla contain at least one neurone most sensitive to fructose and sucrose with a threshold of approximately 0.5 m m . Corresponding to the behavioural data, glucose is significantly less stimulatory to sensilla than fructose or sucrose. It is argued that fructose may be of special importance for herbivorous insects exploiting fruit as an oviposition site.     

Innervation of the cercal sensilla on the ovipositor of the Australian sheep blowfly (Lucilia cuprina)

ABSTRACT. The ovipositor of the female sheep blowfly, Lucilia cuprina (Wied.) (Diptera: Calliphoridae), has a complement of cercal sensilla that includes long, medium and short tactile hairs, two campaniform domes, four olfactory pegs, and ten double-channelled gustatory hairs. This sensory array is suited to assess oviposition site resources, prior to and during the laying of an egg batch.
The tactile hairs and campaniform sensilla are each innervated by a single, tubular body containing dendrite. The olfactory pegs are each innervated by a single, moderately branched dendrite, which gains access to the external environment via pores at the bottom of deep grooves in the peg wall. The gustatory hairs fall into two categories. Four hairs have a single, tubular body containing dendrite at their base, and four unbranched dendrites running up to the hair tip which has a terminal pore. Six of the taste hairs have no tubular body containing dendrite at the base, and three unbranched dendrites running up to a terminal pore.     

Labial tip sensilla of Blissus leucopterus leucopterus (Hemiptera: Blissidae): Ultrastructure and behavior

The cuticular sensory receptors that are found on the apex of the labium of hemipterans play an important role in their feeding behavior. In this study we describe the ultrastructure, number, and distribution of sensilla on the labium apex of the chinch bug, Blissus leucopterus leucopterus. Each apical field of sensilla on the labium contains 11 uniporous peg sensilla and one sensillum chaeticum. The uniporous peg sensilla are innervated by 4–5 bipolar neurons that send dendrites in the lumen of each peg. Three neurons are associated with each sensillum chaeticum, two neurons have dendrites in the lumen of the sensillum, and the third dendrite ends in a tubular body at the base of the sensillum. Behavioral tests that involve chemical blockage of the sensory receptors show the importance of the labial sensilla in feeding behavior. Both morphological and behavioral evidence indicate that the labial sensilla have a chemosensitive function.     

Proboscis sensilla in Vanessa cardui (Nymphalidae, Lepidoptera): functional morphology and significance in flower-probing

 Morphology and distribution of the proboscis sensilla in Vanessa cardui have been investigated in order to contribute to the understanding of flower-probing behaviour in butterflies. The proboscis has a bend region approximately one-third of the length from the base. A short tip region is characterized by rows of intake slits leading into the food canal. Along the dorsal, lateral and ventral sides of the proboscis, sensilla trichodea, sensilla basiconica and sensilla styloconica are distributed in varying patterns depending on their distance from the b ase. The medial food canal bears one longitudinal row of sensilla basiconica only. The bristle-shaped sensilla trichodea are longer in the proximal region of the proboscis and become gradually shorter towards the tip. They are most frequent in number near to the bend region and near the beginning of the tip region. Sensilla basiconica arranged in longitudinal rows increase in number the more distal they are on the proboscis. The tip region is characterized by rows of sensilla styloconica on the dorsal side whereas the sensilla trichodea are mostly restricted to the ventral side. The ultrastructure suggests that the aporous sensilla trichodea function as mechanosensilla while the uniporous sensilla basiconica act as contact chemosensilla. The sensilla styloconica are regarded as bimodal contact chemo/mechanosensilla since their sensory cones are equipped with a single terminal pore and a tubular body at the base. The mouthpart sensilla appear to provide tactile cues on the positioning of the proboscis and on the degree of its insertion into a floral tube. Furthermore, they receive chemical stimuli on the availability of nectar and on the immersion status of the food canal. Accepted: 12 September 1997     

The sensory systems and feeding behavior of leafhoppers. I. The aster leafhopper,Macrosteles fascifrons stål (homoptera,cicadellidae)

The ultrastructure of the sensilla, and other structures, within the stylets and precibarium of Macrosteles fascifrons were examined by transmission and scanning electron microscopy. Precibarium is a new term, defined here, for the canal that precedes the cibarium inside the leafhopper head. Within the precibarium are found 20 chemosensilla and a previously undescribed structure, the precibarial valve. Twelve mechanosensilla, three in each stylet, are found within the maxillary and mandibular stylets. The relationship between all of these structures and feeding by the insect is detailed in a feeding mechanism hypothesis. It is concluded that leafhoppers (and probably all homopterans) utilize the precibarial chemosensilla alone for gustatory discrimination, the stylet sensilla for proprioception, and the precibarial valve for regulation of fluid uptake and compartmentalization of the sensilla.     

Mate recognition and antennal morphology of Octodonta nipae (Coleoptera: Chrysomelidae) adults

The nipa palm hispid beetle, Octodonta nipae (Maulik) has been killing palm trees since its introduction into Hainan province, China, from Malaysia in 2001. It continues to spread within Hainan province, northeast to Fujian province, and northwest to Yunnan province within China. Knowledge on signals involved in mate location and recognition could help develop effective integrated pest management programs. In the present study, we first experimentally proved that antennae were essential in success of O. nipae mating. We then excised various segments/flagellomeres of adult male and female antennae and observed their mating behavior. Results revealed that the 5th to 9th flagellomeres, especially those of males, were important for the mating success. Finally, in an attempt to elucidate the types of antennal sensilla accountable for the mating success, morphology of O. nipae antennae was studied in detail with scanning electron microscopy. Six types of sensilla were distinguished: aporous sensilla trichodea (T1), multiporous sensilla trichodea (T2), aporous sensilla chaetica (Ch1), uniporous sensilla chaetica (Ch2), multiporous sensilla basiconica (B), and Böhm sensilla (Bm). Aporous sensilla trichodea is the most abundant; multiporous sensilla trichodea and sensilla basiconica are considered as olfactory receptors, and uniporous sensilla chaetica as gustatory receptor. Importance of flagellomeres 5–9 in mating success seemed to correspond to the abundance of sensilla on these segments.