Scanning Electron Microscopy Study of the Antennal Sensilla of <Emphasis Type="Italic">Monema flavescens</Emphasis> Walker (Lepidoptera: Limacodidae)

Monema flavescens Walker (Lepidoptera: Limacodidae) is a serious polyphagous defoliator. Using scanning electron microscopy, the external morphology of the antennal sensilla of this pest was examined for a better understanding of the mechanisms of insect-insect and insect-plant chemical communications. The antennae of M. flavescens were filiform in shape, and 11 morphological types of sensilla were found in both sexes. Six types of likely chemosensory sensilla were identified: uniporous sensilla chaetica, multiporous sensilla trichodea, and four types of multiporous sensilla basiconica. The sensilla identified as likely mechanoreceptors included two subtypes of aporous sensilla chaetica, aporous sensilla coeloconica, aporous sensilla styloconica, and Böhm’s bristles, whereas the position of the antennae was monitored by Böhm’s bristles.     

The antennae of neopseustid moths: Morphology and phylogenetic implications, with special reference to the sensilla (Insecta, Lepidoptera, Neopseustidae)

The antennae of Lepidoptera Neopseustidae were examined with the scanning electron microscope. The studied species, Nematocentropus cfr. omeiensis, Neopseustis meyricki, Synempora andesae, Apoplania valdiviana and Apoplania penai possess nine types of antennal flagellum sensilla: multiporous large sensilla basiconica, multiporous thin sensilla basiconica, multiporous small sensilla basiconica, multiporous sensilla trichodea, multiporous sensilla coeloconica; uniporous sensilla chaetica; aporous sensilla chaetica, aporous stylus-shaped sensilla chaetica, aporous sensilla styloconica.The multiporous sensillum type here termed “multiporous large sensillum basiconicum” is unknown from other Lepidoptera and probably constitutes an autapomorphy of the family Neopseustidae. This sensillum type is remarkable by having a single base in female Apoplania and Synempora while in male Apoplania it has a bifid or trifid base, and in male Synempora it is composed of two or three incompletely separated hairs. This may be the first recorded example of a sexually dimorphic lepidopteran sensillum type. The stylus-shaped sensillum chaeticum is a primitive type which occurs only in some lower Lepidoptera.     

Sensilla on the larval antennae and mouthparts of the european sunflower moth,Homoeosoma nebulella Den. and Schiff. (Lepidoptera : Pyralidae)

Sensilla on the larval antennae and mouthparts of Homoeosoma nebulella (Lepidoptera : Pyralidae) were examined with a scanning electron microscope. The antenna possesses 2 aporous sensilla chaetica, one aporous sensillum styloconicum, 3 large multiporous sensilla basiconica, and 3 small multiporous s. basiconica. The labrum bears 12 aporous s. chaetica and the epipharynx has 6 aporous flattened s. chaetica and 4 epipharyngeal sensilla. It is the first time that more than 2 epipharyngeal sensilla have been reported in caterpillars. The mandible possesses 4 aporous s. chaetica. Each galea bears 2 uniporous s. styloconica, 2 small aporous s. basiconica, one s. campaniformium and 3 aporous s. chaetica. Each maxillary palp bears a distal group of 8 uniporous s. basiconica, one large s. digitiformium and one pore plate. Minute grooves exist on the s. digitiformium. Each labial palp possesses one aporous s. chaeticum and one aporous s. styloconicum. An attempt has been made to identify the function of sensilla by comparing them with those of other larvae.     

Sensory Organs on the Antennae of Micropterix calthella L. (Lepidoptera, Micropterigidae)

Antennal sensilla of Micropterix calthella were studied with the scanning electron microscope to determine their morphological types, relative abundance, distribution, location and possible functions. Of the 12 types occurring in both male and female moths, seven are found in most higher Lepidoptera: sensilla trichodea, multiporous s. basiconica, s. coeloconica, s. styloconica, s. chaetica, s. campaniformia and Böhm's bristles. Two types (uniporous s. basiconica and cupuliform organs) are found only in a few families. Three structures are peculiar to Micropterix : ascoïd sensilla, multiporous s. placodea and circular organs. All types of sensilla have characteristic distribution and location pattern similar in both sexes.     

Sensillum types on the proboscis of the Lepidoptera: a review

The external surface of lepidopteran proboscides may bear six morphological types of sensilla: chaeticum, basiconicum, styloconicum, coeloconicum, filiformium, and campaniformium, with the first three types being the most common. There are four types of pore-system: aporous, uniporous, multiporous, and uniporous-multiporous. Sensilla chaetica and campaniformia are aporous sensilla with a tactile or a proprioceptive function, respectively. Aporous sensilla filiformia are probably vibroreceptors. Uniporous sensilla with a gustative function exist in sensilla basiconica, styloconica and coeloconica. Multiporous sensilla were found in long sensilla basiconica and seem rare. Uniporous-multiporous sensilla are relatively common and are to be found both in sensilla styloconica (Arctiidae, Noctuidae) and in sensilla basiconica (Adelidae, Pyralidae, Arctiidae, Noctuidae). It is difficult to establish their function (gustative or olfactive). More extensive research would make it possible to discover them in other families. Only gustative uniporous sensilla basiconica exist in the food canal. The morphology of the proboscis and the distribution of sensilla are adapted to food habits.     

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.     

Antennal sensilla of male Lophocorona pediasia Common 1973 and their phylogenetic implications (Lepidoptera: Lophocoronidae)

The male antennae of Lophocorona pediasia reveal seven types of sensilla: multiporous sensilla trichodea, multiporous sensilla basiconica of subtypes 1 and 2, multiporous sensilla auricillica, aporous sensilla styloconica, multiporous sensilla coeloconica and aporous Böhm’s sensilla. All these sensillum types are present in the higher Lepidoptera. The existence of sensilla auricillica, hitherto denied by several authors, is demonstrated in this study. Typically, they are located on the distal edge of the flagellomeres as in most Lepidoptera. Therefore, their so-called absence must no longer be regarded as an autapomorphy of the Lophocoronidae. Their presence is a common characteristic of all «Dacnonypha», which include, apart from the Lophocoronidae, the Eriocraniidae and the Acanthopteroctetidae. Their number in L. pediasia is smaller than in these two families and more in accordance with the condition found in higher Lepidoptera, suggesting a more advanced position of the Lophocoronidae. The presence of very numerous sensilla basiconica is a possible autapomorphy of the family.     

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.     

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.     

Types of Antennal Sensilla of the Asian Corn Borer,Ostrinia furnacalis (Guenéee)

This study was carried out to investigate the types of sensilla and their distribution on the antennae of the Asian corn borer, Ostrinia furnacalis (Guenéee). O. furnacalis had six types of antennal sensilla: sensilla trichodea, sensilla chaetica, sensilla coeloconica, sensilla auricillica, sensilla styloconica and Böohms bristle. S. auricillica, single-walled multiporous sensilla, were presumed to be involved in chemical reception. S. coeloconica were double-walled, multiporous sensilla and could detect chemicals also. S. chaetica appeared to be mechano-receptors. S. styloconica were poreless and were thought to have thermo- and hygro-receptors. S. trichodea were single-walled chemosensilla and two subtypes were identified by transmission electron microscopy. The scape and the pedicel had Böohms bristles, which seem to function as mechanical stimulus receptors.     

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.     

The antennae and antennal sensilla of the giant looper,Boarmia (Ascotis) selenaria SchiffermÜller (Lepidoptera,Geometridae)*

The general morphology of the antennae and the antennal sensilla of both sexes of Boarmia (Ascotis) selenaria SchiffermÜller are described. The following types of sensilla were found: Bohm bristles and sensilla chaetica, trichodea, coeloconica, auricillica and styloconica. Antennal sexual dimorphism is marked, but mainly confined to the presence of long sensilla trichodea in males and the absence in females. The sensilla trichodea are the most abundant sensillum type.     

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.     

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.     

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.     

Antennal sensilla of male and female of the nut weevil,Curculio nucum Linnaeus, 1758 (Coleoptera: Curculionidae)

The nut weevil, Curculio nucum (Linnaeus, 1758), is the main pest in hazelnut orchards (Corylus avellana L.). Semiochemicals are interesting bio control tools that could be used to manipulate the pest behaviour and to control pest populations. The study of the sensorial equipment of the insect antennae provides information on the importance of olfaction in the adult life for host plants and mate findings as well as on the putative other senses. Before electrophysiological investigation, the knowledge of antennae equipment is also necessary. The aim of this study is to determine the types, number and location of sensilla on the antennae of male and female adult C. nucum in order to determine their implication in seeking a sexual partner and a host plant. The 12-segmented antenna comprises a scape, a 7-segmented funicle and a 4-segmented club. Out of the nine sensillum types listed, three are present on the scape and the funicle and seven types on the club which gathers 71–73% of the total of sensilla. Tactile aporous sensilla chaetica C1, gustatory uniporous sensilla chaetica C2, olfactory multiporous sensilla basiconica B1 and B2 are found on both the dorsal and ventral surfaces of the club in both sexes. Thermo-hygroreceptive dome-shaped sensilla D, olfactory multiporous sensilla basiconica B3 and olfactory multiporous fluted sensilla basiconica F are found exclusively on the ventral surface of the club, suggesting that these sensilla are utilized in host plant acceptance during antennal tapping. The sexual dimorphism concerns only the numbers of sensilla chaetica C1 and sensilla basiconica B2.     

Morphological characteristics of antennal sensilla in the European cornborer Ostrinia nubilalis (Lepidoptera: Pyralidae)

The European cornborer antenna is filiform in both sexes, but exhibits a substantially larger diameter in the males. On the antenna of both sexes, the following sensillum types were characterized: sensilla trichodea, s. basiconica, s. auricillica, s. coeloconica, s. chaetica and s. styloconica. Long dorsal bristles were of a chaetic type. An intermediate trichoid/basiconic type was found in low numbers on the ventral part of the antenna. In the male, three different morphological types of s. trichodea were observed, having one, two or three sensory cells, correlated with different dimensions of the hair. The s. trichodea with three sensory cells are most common in the basal part of the antenna, while sensilla with two cells are mainly found distally. Trichodea with one sensory cell are more evenly distributed over the length of the antenna. All cells present in the different s. trichodea respond to sex pheromone components or to a behavioural antagonist in electrophysiological sensillum recordings. S. basiconica and s. auricillica had 2-3 sensory cells, and a probable olfactory function. Sensilla coeloconica, also with a putative olfactory function, contained 3-5 sensory cells. S. chaetica of the taste/tactile type possessed 4 + 1 sensory cells. S. styloconica comprised three sensory cells with possible functions as thermo- and hygroreccptors.     

Sensilla of the antennal flagellum in Pseudaletia unipuncta (Haw.) (Lepidoptera: Noctuidae)

Seven sensilla were observed on the antennal flagellum of both sexes of Pseudaletia unipuncta (Haw.) (Lepidoptera : Noctuidae): chaetica Type I and Type II), styloconica, coeloconica, trichodea (Type 1a, b, c and Type II a, b), auricillica, nonporous and squamiformia. The major sexual dimorphism noted was the presence of Type la trichodea on the male antennae, suggesting that this sensillum may contain the receptor sites for the female sex pheromone. Differences in the size of sensilla coeloconica, auricillica and trichodea (Types Ib, IIb) were noted between sexes, being larger in females. Adults obtained from larvae fed on artificial diet generally had longer antennae and sensilla than those fed on young oat plants.     

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)。     

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.