Morphology and distribution of sensilia on the cephalic appendages,tarsi and ovipositor of the European sunflower moth,Homoeosoma nebulella Den. & Schiff. (Lepidoptera : Pyralidae)

Sensilla on male and female antennae, mouthparts, tarsi and on the ovipositor of the European sunflower moth, Homoeosoma nebulella (Lepidoptera : Pyralidae) have been investigated by means of scanning electron microscope. The antennal flagellum bears multiporous sensilla (trichodea, basiconica, auricillica, coeloconica) and uniporous sensilla (chaetica, styloconica). A sexual dimorphism is found in the numbers of sensilla trichodea (8300 in males and 6000 in females) and sensilla basiconica (1150 in females and 650 in males). The proboscis has uniporous s. styloconica, multiporous s. basiconica (described for the first time in Lepidoptera), aporous s. chaetica, and some rare uniporous s. basiconica in the food channel. The labial palp-pit organ houses multiporous s. coeloconica, while the maxillary palps have aporous sensilla. Tarsi of both sexes possess one type of aporous s. chaetica and 2 types of uniporous s. chaetica. There is no significant difference in the distribution of tarsal sensilla between males and females. The surface of each lobe of the ovipositor is covered by 3 types of aporous s. trichodea of different lengths and about 60 multiporous s. basiconica, sensilla unusual on the ovipositor of Lepidoptera. The role of sensilla in the oviposition site selection is discussed.     

Antennal sensilla of the click beetle,limonius aeruginosus (OLIVIER) (COLEOPTERA: ELATERIDAE)

Antennal sensilla typology, number and distribution of the click beetle Limonius aeruginosus (Olivier) (Coleoptera: Elateridae) were studied using scanning electron microscopy. The serrate antennae of both sexes of L. aeruginosus consist of the scape, pedicel and of the flagellum which is composed of 9 flagellomeres. In both sexes, 5 types of sensilla basiconica, 1 type of sensilla trichodea, 1 type of sensilla chaetica, 1 type of sensilla campaniformia and Böhm sensilla were distinguished. No remarkable sexual differences in the types, numbers and distribution of sensilla were found on the antennae, except for the sensilla basiconica type II. The average number of sensilla basiconica type II on the antennae of the male beetle surpassed that on the antennae of the female beetle (3562 and 108 pegs, respectively). It is suggested that this type of sensilla on the male beetles antennae is responsible for the reception of the sex pheromone produced by the female beetle.     

Sensilla on the third antennal segment of Drosophila melanogaster meigen (Diptera : Drosophilidae)

The distribution and morphology of the sensilla on the 3rd antennal segment of Drosophila melanogaster Meigen (Diptera : Drosophilidae) were studied with light and electron microscopy. Four types of hairs were identified. Three types of hairs innervated by dendrites are sensilla basiconica, sensilla coeloconica and sensilla trichodea. They occur amongst a large number of the 4th type of uninnervated hairs or spinules.Sensilla basiconica and coeloconica can be easily identified by light microscopy on staining with 0.1016 silver nitrate in 70% ethanol. The tips of sensilla basiconica and coeloconica appear dark brown. Most of the sensilla trichodea and spinules remain unstained.Sensilla basiconica conform to the single-walled, multiporous sensilla, having poretubules and branched dendrites. Sensilla coeloconica are double-walled and have longitudinal channels near the tip. No wall pores are found on sensilla trichodea. Dendrites do not branch in sensilla coelonica and trichodea. A mechanosensory dendrite with characteristic tubular body is absent in these sensilla.Populations of sensilla basiconica and sensilla trichodea occur in diametrically opposite, distinct regions on the 3rd antennal segment-the former in the dorsomedial and the latter in the ventrolateral regions, whereas sensilla coeloconica are distributed on most of the anterior and posterior surfaces, including the cavity walls of the sacculus.The axons are arranged in distinct groups in the antennal nerves at the stalk of the 3rd segment. This grouping becomes more pronounced in the nerve prior to its entry into the brain.     

Atlas of olfactory organs of Drosophila melanogaster: 1. Types,external organization,innervation and distribution of olfactory sensilla

The third antennal segment (funiculus) and the maxillary palp are the main and accessory olfactory sense organs of Drosophila melanogaster. Cryofixed antennae and palps revealed a superior preservation of the sensory dendrites and other cellular details as compared to conventional chemical fixation. Extensive cross-section series through funiculus and palp were studied in order to obtain as complete an evaluation as possible of the sensillar complement on these appendages. About 75% of all sensilla on the male and female funiculus were individually studied and their position on the antennal surface mapped. Dimensions of the cuticular apparatus of the various types of sensilla are provided as well as the number of innervating receptor neurons. Particular attention has been paid to the cuticular pores important for stimulus transport and to the sensory dendrites. On the funiculus surface, all sensilla have multiple wall pores: sensilla (s.) trichodea and s. basiconica are single-walled, s. coeloconica are double-walled. The distribution of s. trichodea and s. basiconica follows opposing gradients along a diagonal axis parallel to the axis of the arista from proximo-medial to disto-lateral. In this disto-lateral direction the density of s. trichodea increases while that of the s. basiconica decreases. S. trichodea occur in three subtypes with one, two or three receptor neurons. Basiconic sensilla can be subdivided into three subtypes of large s. basiconica (with two or four receptor neurons), three subtypes of thin s. basiconica (with mostly two, rarely four neurons), and one subtype of small s. basiconica with two receptor neurons. Large s. basiconica occur only in the most proximal region (the ‘LB-zone’); thin s. basiconica are most common in a belt that borders the LB-zone distally, while small s. basiconica are most numerous even further distally along the mentioned diagonal axis in between the s. trichodea. S. intermedia are single-walled, multiporous sensilla which combine features of s. trichodea and s. basiconica; they are found in two subtypes with two or three receptor neurons, in the same region where s. trichodea abound. The s. coeloconica are irregularly distributed over the funicular surface, and occur in two subtypes with two or three receptor neurons. Sexual dimorphism on the antenna is moderate, the female funiculus is a bit longer and carries a larger number of small s. basiconica and large s. basiconica of the LB-I subtype; the male funiculus, however, has more s. trichodea than the female. On the maxillary palp, besides mechanoreceptive s. chaetica, there are only s. basiconica with two receptor neurons. According to the fine structure of their sensory dendrites, three subtypes can be discriminated which are distributed in a random pattern. The functional significance of the described structures and distribution awaits future immunocytochemical and electrophysiological experiments.     

黄脊竹蝗触角感器的电镜扫描观察

黄脊竹蝗是中国南方地区重要的竹子害虫,为了更好地理解黄脊竹蝗"趋尿行为"的生理生化机制,通过电镜扫描技术研究了黄脊竹蝗成虫触角感器的类型、数量、形态及分布特征,比较分析了其在雌、雄成虫间的差异。结果表明:黄脊竹蝗雌、雄成虫触角丝状,由1节柄节、1节梗节和23节鞭节构成,雌雄间触角长度及直径差异不显著(P>0.05);雌、雄成虫触角感器均有毛形感器Ⅰ、毛形感器Ⅱ、刺形感器、锥形感器Ⅰ、锥形感器Ⅱ和腔锥形感器6种;其中,锥形感器数量最多,约占感器总数的53%,主要分布在鞭节的第8～21亚节上;各类感器在雌、雄成虫间触角上的分布特征相似,雄成虫触角上感器总数、锥形和腔锥形感器数量显著多于雌成虫(P<0.05)。     

Antennal sensilla of the ground beetle Bembidion lampros Hbst (Coleoptera, Carabidae)

Antennal sensilla typology, number and distribution pattern were studied in the ground beetle Bembidion lampros Hbst (Coleoptera, Carabidae) using scanning electron microscopy. The 1.6–1.8 mm long filiform antennae of both sexes consist of the scape, pedicel and of the flagellum composed of nine flagellomeres. In both sexes, three types of sensilla chaetica, two types of sensilla trichodea, five types of sensilla basiconica, one type of sensilla coeloconica, one type of sensilla campaniformia and Böhm sensilla were distinguished. The possible function of the sensilla was discussed and three types of sensilla were considered as olfactory, sensilla trichodea type 2 and sensilla basiconica types 1 and 2. Olfactory sensilla occupy dorsal and/or ventral areas of the flagellomeres and occur sparsely (sensilla basiconica type 1) or not at all (sensilla basiconica type 2 and sensilla trichodea type 2) outside these areas. No remarkable sexual differences in the types, numbers and distribution of antennal sensilla were found.     

Morphology and distribution of antennal sensilla of the tarnished plant bug,Lygus lineolaris (Palisot de beauvois) (Hemiptera: Miridae)

Sensilla on the antennae of adult and last-instar nymphs of the tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae), were examined with light, scanning and transmission electron microscopy. Six different types were identified in adult females and males and 5 types in last-instar nymphs: types 1 and 4 are sensilla trichodea, 2 and 3 are sensilla chaetica, and 5 and 6 are sensilla basiconica. Type 1 are located at distal region of terminal segment and type 2 are located at distal regions of proximal 3 segments in both adults and nymphs. Type 3 is present on all segments, more numerous on scape and pedicel and less abundant on distal third and fourth segments in both adult and nymphal stages. Types 4 and 6 are absent on the scape and present on the distal 3 antennal segments in adults, but they are present only on the distal-most antennal segment in nymphs. Type 5 sensilla are present only on second antennal segments in adults and are absent in nymphs. Sexual dimorphism is observed in total numbers: there are significantly more type(s) 3, 4, 5 and 6 sensilla in adult males than adult females. Types 1, 4 and 5 are multiporous with thin cuticle, branched dendrites and pore tubules which suggests an olfactory function. These sensilla have 3, 3 and 2 neurons, respectively. The type 6 sensillum has an apical pore and pores in the cuticular wall, and is innervated by 5 nerve cells with unbranched dendrites. Sensillar types 2 and 3 have thick cuticle, a single apical pore and nerve cells with unbranched dendrites. Type 2 has 1 neuron and type 3 has 2 chambers and 2 nerve cells.     

Antennal sensilla in adult Agathiphaga vitiensis dumbl. and A. queenslandensis dumbl. (Lepidoptera : Agathiphagidae)

The antennae of both sexes of Agathiphaga vitiensis and the antenna of the female of A. queenslandensis (Lepidoptera : Agathiphagidae) were studied with a scanning electron microscope. In both sexes, 10 types of sensilla were observed on the antennae of A. vitiensis: Böhm's bristles, chaetica (types I and II), squamiformia, trichodea, biforked basiconica, short basiconica and coeloconica (types I, II and III). The female of A. queenslandensis possesses the same types of sensilla, except that the biforked basiconica are flattened. Biforked sensillum basiconicum is being reported in Lepidoptera for the first time. Their presence supports Kristensen's hypothesis on the phylogeny of Lepidoptera (1984). The female of A. vitiensis possesses more sensilla than that of A. queenslandensis. The male of A. vitiensis has a greater number of s. trichodea than the female, but the biforked sensilla basiconica are more numerous on the female antenna than on the male one.     

Olfactory responses and sensilla morphology of the blackcurrant leaf midge Dasineura tetensi

Olfactory responses of Dasineura tetensi (Rubs) (Diptera; Cecidomyiidae) to leaf volatiles of blackcurrant (Ribes nigrum) were tested in a 4-way olfactometer. Newly emerged virgin females showed no response to the leaf volatiles emitted from a blackcurrant shoot. Newly emerged males (which are known to respond to a pheromone released by the female) also showed no response to the leaf volatiles. Two hours after mating females responded positively, indicating that leaf volatiles may play a role in host plant finding. Scanning (SEM) and transmission (TEM) electron microscopy of the antennae of D. tetensi showed that males and females share five sensillum types; sensilla chaetica (mechanoreceptors), sensilla trichodea, sensilla basiconica, uniporous peg sensilla and circumfila (chemoreceptors). The sensilla chaetica and sensilla trichodea resemble those found on other insects. Sensilla basiconica were found on all antennal subsegments except the tip. These are multiporous receptors with five unbranched dendrites filling the lumen. Small peg sensilla located on the tips of both male and female antennae may function as contact-chemoreceptors. The circumfila, which are a unique type of sensilla found only on cecidomyiid antennae, form loops around each of the antennal subsegments, being attached to the surface by a series of stalks. TEM revealed that each stalk consisted of one sensillum containing a single highly branched dendrite. The distal regions of the walls of each sensillum are fused together to form the circumfila. Circumfila have multiporous walls and a lumen filled with multiple branches of dendrites. Their structure suggests that they are important olfactory receptors in both the male and female.     

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.     

Structure and distribution of antennal sensilla in Oranmorpha guerinii (Gervais, 1837) (Diplopoda,Polydesmida)

Detailed information on sensory organs of Diplopoda especially on antennal sensilla are still sparse and fragmentary. The present study on the antennae of Oranmorpha guerinii (Polydesmida, Paradoxosomatidae) utilizing scanning electron microscopy revealed the presence of six sensillar types: (1) apical cones, (2) sensilla trichodea, (3) sensilla microtrichodea, (4) sensilla chaetica, (5) sensilla basiconica bacilliformia, and (6) sensilla basiconica spiniformia. External structure and distribution of cuticular antennal sensilla are compared with data from other diplopod species. We moreover discuss possible functions of antennal sensilla in millipedes.     

Antennal sensilla of male and female Telenomus reynoldsi gordh and coker (Hymenoptera : Scelionidae)

Sensilla on the antennae of both sexes of Telenomus reynoldsi (Hymenoptera : Scelionidae) were studied with the scanning electron microscope to determine their structure and possible function in mating and host recognition. Two types of setiform sensilla occur: curved, grooved sensilla trichodea and erect, stout sensilla chaetica. Horn-like sensilla trichodea curvata are abundant on the male antennae, but are less abundant and only present dorsally on the female. Sensilla basiconica are unique to the ventral surface of the apical 4 segments of the female antennae. Sensilla styloconica are located on A4 and A10 of the female and A7 and A9 of the male. Multiporous grooved sensilla are present on A4, A6, and A11 of the female and A4 and A6-A11 of the male. A possible sex gland is located on the venter of A5 of the male. The functions of sensilla trichodea curvata and sensilla basiconica in courtship and host recognition, respectively, are hypothesized by correlation with behavioral observations.     

Olfactory sensilla on the antenna and maxillary palp of the sheep head fly,Hydrotaea irritans (Fallen) (Diptera : Muscidae)

Antennae and maxillary palps of both sexes of the Sheep Head fly Hydrotaea irritans (Diptera : Muscidae) were investigated using scanning electron microscopy to describe the types, morphology, and distribution of olfactory sensory structures. Only socketed bristles and microtrichia were found on the scape of the antennae. These structures were also observed on the pedicel together with a group of 7–8 as yet undescribed sensilla, whose function is unknown. Olfactory sensilla were not found on these 2 segments or on the arista. Large numbers of olfactory sensilla and microtrichia were present on the funiculus. The former included sensilla trichodea (thick-walled, multiporous sensilla), sensilla styloconica and 6 types of sensilla basiconica (thin-walled, multiporous sensilla), 4 of which occurred individually and 2 of which were found in groups. An olfactory pit containing groups of thin-walled multiporous sensilla was located on the dorsomedian side of the funiculus. All sensilla basiconica were classified on morphological characteristics. The maxillary palps were covered with microtrichia and socketed bristles, but only 1 type of olfactory sensillum was found. This was a type of sensillum basiconicum that differed from any of those found on the antennae. No differences were found in sensilla diversity and distribution between males and females.     

Morphology and distribution of antennal sensilla in the pine wood nematode insect vectors Monochamus alternatus Hope and Monochamus saltuarius Gebler (Coleoptera: Cerambycidae)

As insect vectors of pine wood nematodes, Monochamus alternatus Hope and Monochamus saltuarius Gebler have different levels of attractiveness to semiochemicals. Although active use of chemical communication in both species is well known, there was no report on the differences in morphology and distribution of antennal sensilla between the two Monochamus species. The present study was carried out to explore the morphology, distribution, and ultrastructure of antennal sensilla of the two species using scanning and transmission electron microscopy. The overall shapes of the antennae were not different between M. alternatus and M. saltuarius. However, both M. alternatus and M. saltuarius exhibited sexual dimorphism overall. The antennae of each species were composed of the scape, pedicel, and nine flagellomeres, with four morphological types of sensilla: trichodea, basiconica, chaetica, and coeloconica. The four types occurred in varying numbers and distributions. The sensilla chaetica type was the most abundant in both species. Three types of sensilla (trichodea, basiconica, and chaetica) could be subdivided according to the two Monochamus species; sensilla trichodea could be divided into two subtypes, and sensilla basiconica and sensilla chaetica into three. All sensilla basiconica subtypes were multiporous, indicating that their primary function was olfactory. Sensilla trichodea subtype 2 was uniporous, indicating that the function of these sensilla might be gustatory. The morphological information obtained in our study provides a basis for future investigation of the sensory physiological function of each type of sensilla in the two species.     

Flagellar Sensilla of Sphecodes Bees (Hymenoptera, Halictidae)

The antenna of Sphecodes bees were investigated as regards the type and distribution of the sensilla. Eleven species originating from Sweden were used. Totally 325 specimens were studied. The distribution of sensilla placodea and sensilla trichodea on the antennal segments were studied in the light stereomicroscope. One to three antennae per species were also examined by SEM. The following types of sensilla were found: s. placodea; pit organs; s. campaniformia; s. basiconica; s. trichodea A, B and CD; and setae. The distribution of sensilla, especially s. placodea and s. trichodea A, was found to be species-specific in the male sex and their diagnostic value in taxonomy is stressed. In the female sex no specific characteristics were found, although two groups could be distinguished.     

Fine structure and distribution of antennal sensilla of the desert locust, Schistocerca gregaria (Orthoptera: Acrididae)

The fine structure and distribution of various types of antennal sensilla in three nymphal stages and in adults of both solitary-reared (solitary) and crowd-reared (gregarious) phases of the desert locust, Schistocerca gregaria, were investigated by scanning and transmission electron microscopy. Four types of sensilla were identified: sensilla basiconica, s. trichodea, s. coeloconica and s. chaetica. S. basiconica contain up to 50 sensory neurons, each of which displays massive dendritic branching. The sensillar wall is penetrated by a large number of pores. In contrast, s. trichodea contain one to three sensory neurons that branch to give five or six dendrites in the sensillar lumen; the sensillum wall is penetrated by relatively few pores. The s. coeloconica are situated in spherical cuticular pits on the antennal surface. The s. coeloconica are of two types: one type contains one to three sensory neurons with double sensillar walls penetrated by slit-like pores, whereas the second type contains four sensory neurons with non-porous double sensillar walls. The s. chaetica have a flexible socket and a thick non-porous sensillum wall and contain four sensory neurons that send unbranched dendrites to a terminal pore. A fifth sensory neuron of the s. chaetica terminates in a tubular body at the base of the hair. S. basiconica and coeloconica are normally distributed over the entire antennal flagellum, with a concentration in the middle segments; s. trichodea have three areas of concentration on the 5th, 10th and 14th flagellar segments. Sensilla chaetica are most abundant on the terminal segment. Locusts raised in solitary conditions have more olfactory sensilla (s. basiconica and s. coeloconica) than crowd-reared locusts. The difference in sensillar numbers is more evident in adults than in nymphs. These results suggest that differences in the odour-mediated behaviour of nymphs and adults, and between the phases of S. gregaria, may be attributable to differences at the sensory input level.     

Morphology of antennal sensilla of the brown spruce longhorn beetle,Tetropium fuscum (Fabr.) (Coleoptera: Cerambycidae)

The antennal sensilla of the brown spruce longhorn beetle, Tetropium fuscum (Fabr.) (Coleoptera: Cerambycidae) were examined with particular focus on the sensilla present on the apical flagellomere. T. fuscum antennae are composed of 11 segments, namely the scape, pedicel, and nine flagellomeres. Nine types of sensilla were observed: three types of sensilla chaetica, sensilla trichodea, two types of sensilla basiconica, grooved peg sensilla, thick-walled sensilla, and Böhm bristles. Seven of these types were present on the apical flagellomere, the exceptions were sensilla chaetica type 3 and Böhm bristles. There were no significant differences in the distribution or density of sensilla present on the ninth flagellomere of males and females, except that males had significantly more sensilla chaetica type 1, which are put forward as the putative contact chemoreceptors for T. fuscum.