Morphological and genetic differences in legs of a polygamous beetle between sexes, Glenea cantor (Coleopter: Cerambycidae: Lamiinae).

The legs of insects play an important role in their daily behaviour, especially reproduction. Entomologists have performed much research on the role of the leg in different behaviours of beetles, an important group in the insect family, but relatively little has been done to study the ultrastructure and transcriptome of their legs. Hence, we systematically studied the ultrastructure and gene expression of the leg of G. cantor, a polygynous beetle, and compared its male and female diversity. In this study, we found the fore-leg, mid-leg and hind-leg of the female were significantly longer than those of the male. From the perspective of intuitive structural differences, we also compared the ultrastructures of the adhesion structure (tarsal) of males and females. The tarsal functional structure of the adult leg mainly includes sensilla and an adhesion structure. The sensilla on the tarsal joint mainly include sensilla chaetica (SCh II, SCh III) and sensilla trichodea (ST II). The adhesion structure includes disc-shaped bristles (di), lanceolate bristles (la), serrated bristles (se), spatula-shaped bristles (spl) and mushroom-shaped bristles (mus). Although there was no significant difference in sensillum distribution or type between males and females, there were significant differences in the distribution and species of adhesion structures between the fore-leg, mid-leg, and hind-leg of the same sex and between males and females. Therefore, different adhesion structures play different roles in various behaviours of beetles. On the other hand, the transcriptome results of male and female legs were screened for a subset of olfaction- and mechanics-related genes. We discovered that the male leg showed upregulation of 1 odorant binding protein (OBP), 2 Olfactory receptors (ORs) and 2 Chemosensory proteins (CSPs). Meanwhile, the female leg showed upregulation of 3 OBPs, 1 OR, 1 Gustatory receptor (GR) and 3 Mechanosensitive proteins (MSPs). An in-depth examination of the ultrastructure and molecular composition of the legs can elucidate its function in the reproductive behavior of G. cantor. Moremore, this investigation will serve as a cornerstone for subsequent research into the underlying behavioral mechanisms.

Morphology and distribution of sensilla on antennae and mouthparts of the adult bruchid beetles, Bruchidius coreanus (Coleoptera: Bruchidae).

Bruchidius coreanus is a serious pest on Gleditsia sinensis Lam during seed storage, causing significant losses to their yield in southwest China. To gain insight into their behavioral mechanisms, the external morphology, ultrastructure, and distribution of sensilla on antennae, maxillary palps, and labial palps of both male and female B. coreanus were observed using a scanning electron microscope. The results revealed that both male and female adults had serrated antennae comprising a scape, a pedicel, and nine flagellomeres (F1-F9). There were eight types and seven subtypes of antenna sensilla observed in both sexes, including Böhm sensilla (BS), two subtypes of sensilla chaetica (SC1 and SC2), two subtypes of sensilla trichodea (ST1 and ST2), three subtypes of sensilla basiconica (SB1, SB2, and SB3), sensilla auricillica (SA), sensilla styloconicum (SS), capitate pegs (CP), and sensilla cavity (SCa). The average length of BS and ST (ST1 and ST2) showed significant differences between males and females. Furthermore, the number of SC (SC1 and SC2), ST1, and SCa differed significantly between the sexes. Four types of sensilla were found on the maxillary palps and labial palps, with the length of ST on these palps significantly differing between males and females. Additionally, SS on male labial palps was significantly longer than in females. The number of SC significantly differed between the male and female maxillary palps and labial palps, while ST and SS showed significant differences in the maxillary palps. These findings will contribute to further electrophysiological recording and behavioral research. RESEARCH HIGHLIGHTS: The external morphology and distribution of various sensilla on the antennae, maxillary palps, and labial palps of Bruchidius coreanus were described. Eight types and seven subtypes of antenna sensilla were observed on the antennae, while four types of sensilla were observed on the maxillary palps and labial palps. The capitate pegs were found exclusively on the antennae of female B. coreanus.

Microscopic morphology and distribution of the antennal sensilla in the double-spined bark beetle, Ips duplicatus (Coleoptera: Curculionidae).

The double-spined spruce bark beetle, Ips duplicatus, has become an infamous secondary pest of Norway spruce, causing extensive ecological and economic destruction in many Central European countries. Antennae are the primary olfactory organs that play a fundamental role in insect-host chemical communication; therefore, understanding morphology is crucial before conducting electrophysiological investigations. Here, we present our analysis of sensilla types on the antennal surface of I. duplicatus for the first time, using high-resolution-scanning electron microscopy. We studied the external morphological characteristics of antennae and the types, numbers, and distribution of the antennal sensilla in males and females. Our results revealed the presence of five different types of morphologically distinct sensilla: sensilla chaetica, sensilla basiconica, sensilla trichodea, sensilla coeloconica, and Böhm's sensilla. We observed two subtypes of sensilla chaetica (SChI and SChII), four subtypes of sensilla basiconica (SBI, SBII, SBIII, and SBIV), three subtypes of sensilla trichodea (STrII, STrIII, and STrIV) and two subtypes of sensilla coeloconica (SCoI and SCoII), respectively in I. duplicatus males and females. Minor differences in length and numbers between the sexes for some sensilla types were found. Distribution maps for different sensillar types were constructed, and specific areas for the respective sensilla were found. Possible functions of observed sensilla types are discussed. The present study provides a basis for future electrophysiological studies to understand how I. duplicatus detects ecologically important olfactory cues. RESEARCH HIGHLIGHTS: • The first report of morphology and distribution pattern of the antennal sensilla in Ips duplicatus is discussed. • A total of 6 main types and 11 antennal sensilla subtypes were observed in male and female Ips duplicatus. • Minor sex-specific differences were seen in the length and numbers in several sensilla types.

Observations on the ultrastructure of the oral appendages of Glenea cantor Fabricius (Coleoptera: Lamiinae).

Using scanning electron microscopy, we examined the gross and ultrastructure morphology of the mandibles, labial palpi, and mandibular palpi of adult male and female Glenea cantor beetles. The morphology of these parts, both in their gross and ultrastructure, varied significantly between males and females. The lengths of the mandible, labial palpi, and mandibular palpi were clearly noticeably longer in females than in men, which is mostly related to the oviposition mechanism. In terms of the ultrastructural morphology of the mandibles, labial palpi, and mandibular palpi, seven types of sensilla were found on these parts: sensilla twig basiconica (STB I, II, III, and IV), sensilla chaetica (Scheme IV and V), Böhm's bristles (Bb), sensilla placodea (SP), sensilla trichodea (ST II), sensilla plate (SP), sensilla coeloconica (SC), and sensilla campaniformia (SCa). Females have significantly more ST I and Scheme III on their mandibles than males. The mechanical sensors SCh and Bb, olfactory sensor ST II, taste sensor STB IV, and carbon dioxide sensor and temperature and humidity sensors SC, SP, and SCa were much more developed on the labial and maxillary palpi of females compared to those of males, which further clarified the significance of the oral appendages in oviposition behavior. These findings will advance information-based technique design and the creation of information-based pest control strategies by assisting in our understanding of the host preference and oviposition behavior of adult G. cantor. RESEARCH HIGHLIGHTS: The external morphology and distribution of the oral appendages of Glenea cantor between sexes has been researched through scanning electron microscopy (SEM) for the first time. Several significant differences between males and females have been found by analyzing the oral appendages of G. cantor with SEM. The differences in the structure of oral appendages of G. cantor between sexes reflect functional differences in reproductive behaviors.

First description of the male genitalia in a short-tailed whipscorpion (Arachnida: Schizomida), description of the female, and comments on pygidial glands and cuticular ultrastructure of Surazomus algodoal Ruiz & Valente, 2017.

The male genitalia of Surazomus algodoal Ruiz & Valente, 2017 are described. Since this is the first attempt to describe male genitalia in the schizomids, we propose new terminology to describe the sclerites of the male genital chamber in the order. We believe that the male genitalia may provide a large set of characters for taxonomic research in schizomids, as the female genitalia have proven to do. The setae and other cuticular structures were investigated using light and scanning electron microscopy (SEM). The female of S. algodoal is described for the first time, including the genitalia, and we highlight the sexual dimorphism present in the species. We also present descriptions of: 1) microtrichia, with respect to their presence/length/distribution, 2) cuticular sensilla, glandular openings and other cuticular structures, proposing new terminology, 3) setae of the pedipalpal trochanter and tarsus. Some changes on the terminology of setae of pedipalpal tibia are also given. These advances may be useful for description in other schizomids. The pygidial glands, mostly ignored in modern papers, were assessed and commented upon.

Morphology and location of sensilla in the antennae and ovipositor of Sirex noctilio (Hymenoptera: Siricidae).

The woodwasp Sirex noctilio Fabricius is a major quarantine pest that was reported in China in 2013 and mostly damages Pinus sylvestris var. mongolica. Reverse chemical ecology, which uses chemical lures to catch or block insects from mating is the classic way to control forestry pests. This indicates that insect sensilla play a crucial role in detecting external chemical and physical stimuli. Nonetheless, the categorization and distribution of sensilla on the antennae and ovipositor of S. noctilio are insufficiently specific. In this paper, scanning electron microscopy (SEM) was used to observe the ultrastructure of the sensilla of S. noctilio on the antenna and ovipositor. It was found that the types and distribution of sensilla on the antennae of S. noctilio male and female are consistent, and six types of sensilla are found: sensilla trichodea (ST), sensilla chaetica (SC), Böhm bristles (BB), sensilla basiconica (SB), sensilla ampullacea (SA), and contact chemoreceptors (CC). Besides, there are five types of sensilla on the female ovipositor. In addition to ST, SC and BB, two more types of sensilla are also found: sensilla cavity (SCa) and sensilla coeloconica (SCo). Through identification of the morphology and distribution of the sensilla, the functions of different sensilla in the mating and host selection mechanisms of S. noctilio are proposed, thereby establishing a foundation for S. noctilio chemical communication research.

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.

Scanning electron microscopic studies of the antennal sensilla of Aplosonyx chalybaeus (Hope) (Coleoptera: Chrysomelidae).

Aplosonyx chalybaeus is a major insect pest of the plant Colocasia which is commonly found in the North-Eastern region of India. The antenna of A. chalybaeus is filiform, composed of a scape, a pedicel, and a flagellum with nine flagellomeres. The type, structure, and distribution of sensilla, on the antennae of the adult A. chalybaeus (Coleoptera: Chrysomelidae), were examined by scanning electron microscopy. Eight different types of sensilla were observed on the antennae using scanning electron microscopy, that is, sensilla trichodea, sensilla chaetica, sensilla basiconica, multiporous grooved pegs, sensilla auricillica, sensilla styloconica, glandular plates, and Böhm sensilla based on their external morphology. Distribution of all the antennal sensilla observed was discussed on the antenna. In addition, we discussed the putative functions of all the sensilla observed based on their external morphological and distributional characteristics on the antenna of the species. RESEARCH HIGHLIGHTS: • External morphology and distribution of various antennal sensilla in male and female of Aplosonyx chalybaeus were described. • Eight types with 17 subtypes of antennal sensilla were observed. • Distinct sexual dimorphism was observed in occurrence and distribution of various sensilla.

Comparative morphology of antennal ultrastructure in Tachinidae parasitoid flies (Diptera): The phylogenetic importance of antennal sensilla.

Tachinidae are one of the most diverse clades of Diptera. All tachinids are parasitoids of insects and other arthropods, and thus are considered an important source of biological pest control. Antennae are the most important olfactory organs of Tachinidae playing key roles in their lives, especially in locating hosts, and details of antennal ultrastructure could provide useful features for phylogenetic studies and understanding their adaptive evolution. Despite the ecological and evolutionary importance of antennae, the current knowledge of antennal ultrastructure is scarce for Tachinidae. Our study examined antennal sensilla of thirteen species belonging to thirteen genera within eleven tribes of all the four subfamilies (Phasiinae, Dexiinae, Tachininae, and Exoristinae): Beskia aelops Walker, Trichodura sp., Voria ruralis (Fallén), Zelia sp., Cylindromyia carinata Townsend, Phasia xenos Townsend, Neomintho sp., Genea australis (Townsend), Copecrypta sp., Hystricia sp., Belvosia sp., Leschenaultia sp., and Winthemia pinguis (Fabricius). Types, length and distribution of antennal sensilla were investigated via scanning electron microscopy (SEM). Our comparative analysis summarized 29 variable characters and we evaluated their phylogenetic signal for subfamilial, tribal and generic/specific levels, showing that antennal ultrastructure could be a reliable source of characters for phylogenetic analysis. Our findings demonstrate the remarkable diversity of the antennal ultrastructure of Tachinidae.

Ultrastructure and distribution of sensory receptors on the nonolfactory organs of the soldier caste in subterranean termite (Coptotermes spp.).

The soldier caste of termites uses sensilla to sense pheromonal, tactile, and vibrational cues to communicate inside and outside their nest. Although sensilla with many modalities on the antennae of subterranean termites have been well explored, there remains a lack of information regarding sensillum characteristics and distribution of the nonolfactory organs of the soldier caste in the Coptotermes genus. In this study, the ultrastructure of sensilla from the soldier caste of three Coptotermes spp. (Coptotermes formosanus, Coptotermes curvignathus, and Coptotermes gestroi) was observed by scanning and transmission electron microscopy, and the putative function of each type was deduced. Six total sensillum types were observed, with two mechanoreceptive sensillum types (hair and plate). The long flexible-peg mechanoreceptive sensilla may work as contact-chemoreceptive sensilla due to their elongated dendritic outer segments and uniporous characteristics. There was a significant depletion of mechano-chemoreceptive sensillum numbers in C. gestroi, which was compensated by a high density of short-peg mechanoreceptive sensilla on the pronotum. Finally, cuticular and innervation characteristics of thermo-/hygrosensitive sensilla were observed for the first time on the labrum of the soldier caste of Coptotermes.

Ultrastructure of sensilla on the antennae and maxillary palpi of the human-biting black flies, Simulium nigrogilvum and Simulium umphangense, (Diptera: Simuliidae) in Thailand.

Antennae and maxillary palpi are the most important sensory organs involved in the behaviors of black flies. The ultrastructure of sensilla on these sensory appendages of two human-biting black fly species, Similium nigrogilvum and Simulium umphangense, was studied for the first time. Wild adult females of both species were collected in Umphang District, Tak Province, western Thailand. The morphology and distribution of sensilla were examined using scanning electron microscopy. Overall, the morphology of the antennae and maxillary palpi and distribution of sensilla are similar in the two species. Four major types of sensilla were found on the antennae of both species: sensilla basiconica (three subtypes), coeloconica, chaetica (four subtypes), and trichodea. However, sensilla basiconica subtype IV are only present on the antennal surface of S. nigrogilvum. Sensilla trichodea are the most abundant among the four types of sensilla that occur on the antennae of both species. Significant differences in the length of the antennae (scape and flagellomere IX), length of the maxillary palpi (whole and palpal segments I, III, IV and V), and the length and basal width of four sensilla types (trichodea, chaetica, basiconica, and coeloconica) were found. In addition, two types of sensilla were observed on the maxillary palpi: sensilla chaetica (three subtypes) and bulb-shaped sensilla. Differences were observed in the numbers of bulb-shaped sensilla in the sensory vesicles of S. nigrogilvum and S. umphangense. The findings are compared with the sensilla of other insects, and the probable functions of each sensillum type are discussed. The anatomical data on sensory organs derived from this study will help to better understand black fly behavior.

The variability of antennal sensilla in Naucoridae (Heteroptera: Nepomorpha).

The morphology and distribution of sensilla on the surface of the antennae of the naucorids' species were studied via scanning electron microscopy. Eleven types of sensilla were identified regarding specific sensory modalities, based on their cuticular morphology. Cuticle morphology identifies five types of sensilla trichodea, four types of sensilla basiconica, one type of sensillum coeloconicum and sensillum ampullaceum. Three new types of mechanosensitive sensilla were found. Moreover, the morphological diversity between the antennae allowed the distinction of ten different antennal types that correspond to different sensillar sets. The sensilla found in Naucoridae share similarities with the sensilla of other nepomorphan taxa, as well as of terrestrial insects. However, no sensillar synapomorphy was found between Naucoridae and Aphelocheiridae.

Antennal and palpal sensilla of three predatory Lispe species (Diptera: Muscidae): an ultrastructural investigation.

Antennae and maxillary palps are the most important chemical reception organs of flies. So far, the morphology of antennae and maxillary palps of flies of most feeding habits have been well described, except for that of relatively rare aquatic predatory species. This study describes sensilla on antennae and maxillary palps of three aquatic predatory Lispe species: Lispe longicollis, L. orientalis and L. pygmaea. Types, distribution, and density of sensilla are characterised via light and scanning electron microscopy. One type of mechanoreceptors is found on antennal scape. Mechanoreceptors (two subtypes) and one single pedicellar button (in L. pygmaea) are located on antennal pedicel. Four types of sensilla are discovered on antennal postpedicel: trichoid sensilla, basiconic sensilla (three subtypes), coeloconic sensilla and clavate sensilla. A unique character of these Lispe species is that the coeloconic sensilla are distributed sparsely on antennal postpedicel. Mechanoreceptors and basiconic sensilla are observed on the surface of maxillary palps in all three species. We demonstrated clear sexual dimorphism of the maxillary palps in some of the Lispe species, unlike most other Muscidae species, are larger in males than females. This, along with their courtship dance behaviour, suggest their function as both chemical signal receiver and visual signal conveyer, which is among the few records of a chemical reception organ act as a signal conveyer in insects.

Morphological Characterization of the Antennal Sensilla of the Afrotropical Sand Fly, Phlebotomus duboscqi (Diptera: Psychodidae).

We investigated by scanning electron microscopy the morphology, distribution, and abundance of antennal sensilla of females Phlebotomus duboscqi sand fly, an important vector of zoonotic cutaneous leishmaniasis at Afrotropical region. Thirteen well-differentiated sensilla were identified, among six types of cuticular sensilla. The probable function of these sensillary types is discussed in relation to their external structure and distribution. Five sensillary types were classified as olfactory sensilla, as they have specific morphological characters of sensilla with this function. Number and distribution of sensilla significantly differed between antennal segments. The results of the present work, besides corroborating in the expansion of the morphological and ultrastructural knowledge of P. duboscqi, can foment future electrophysiological studies for the development of volatile semiochemicals, to be used as attractants in traps for monitoring and selective vector control of this sand fly.

The Behavioral Response to Heat in the Common Bed Bug, Cimex lectularius (Hemiptera: Cimicidae).

The bed bug, Cimex lectularius L., is a common ectoparasite found to live among its vertebrate hosts. Antennal segments in bugs are critical for sensing multiple cues in the environment for survival. To determine whether the thermo receptors of bed bugs are located on their antennae; innovative bioassays were created to observe the choice between heated and unheated stimuli and to characterize the response of bugs to a heat source. Additionally, the effect of complete antenectomized segments on heat detection were evaluated. Heat, carbon dioxide, and moisture are cues that are found to activate bed bug behavior; a temperature at 38°C was used to assess the direction/degree at which the insect reacts to the change in distance from said stimulus. Using a lightweight spherical ball suspended by air through a vacuum tube, bed bugs and other insects are able to move in 360° while on a stationary point. Noldus EthoVision XT was used to capture video images and to track the bed bugs during 5-min bioassays. A bioassay was created using four Petri dish arenas to observe bed bug attraction to heat based on antennae segments at 40°C. The purpose of this study was to evaluate the effects of heat on complete antenectomized segments of the antennae. The results in this experiment suggest that bed bugs detect and are attracted to heat modulated by nutritional status. Learning the involvement of antennae segments in heat detection will help identify the location and role of thermoreceptors for bed bug host interaction.

Variation of cleaning organ structures and setae of pedipalp tarsus in the family Phrynidae (Arachnida: Amblypygi).

The pedipalp tarsus of Amblypygi is used as a cleaning tool in grooming behavior and as a weapon in prey capture. The tarsus presents several structures with unknown functions that probably relate to both processes. The Amblypygi tarsus possesses a cleaning organ with two lines of projections and a group of setae distributed along the structure. We analyzed the morphological variation of the cleaning organ structures and the setae of the tarsus in species of the family Phrynidae using scanning electron microscopy (SEM). Additionally, we made histological sections to evaluate the sensory function of the structures. We found variation in the shape and size of the setae, projections and granular area of the cleaning organ; however, the observed differences do not allow for differentiation of taxonomic genera. The setae and projections of the cleaning organ have an internal structure similar to tip-pore sensilla. Externally, the setae are similar to the sensorial hairs in spiders and differ from the cleaning organ projections, which probably are modified setae. Mechanoreception function is evident in the setae, and is probable in projections of the cleaning organ; the evidence observed indicates that both structures may be considered as putative chemoreceptors.

Antennal morphology and sensilla ultrastructure of Ascia monuste (Linnaeus) (Lepidoptera: Pieridae).

Insects have different types of cuticular sensory structures, called sensilla, which are employed in environmental perception due to their direct connection to the nervous system. Antennae are the main structures containing these sensilla in Lepidoptera. This study used scanning electron microscopy to describe the general morphology and the types of antennal sensilla of the great southern white butterfly, Ascia monuste, an important pest that feeds on cruciferous plants during its larval stages. Organizational, distributional, and functional aspects are comparatively discussed, as well as potential sexual dimorphism. Sensilla and general morphology were analyzed using a stereomicroscope and photomicrographs in the ImageJ software. Four types of sensilla were found in males and females: sensilla trichodea, chaetica, basiconica and coeloconica. The number of flagellomeres was different between sexes, with females having more articles and a longer antennal length than males. The capitate antenna of this butterfly had a unique elliptical central sulcus in the median ventral surface of each segment, mostly containing sensilla trichodea. Some organizational aspects of the sensilla chaetica close to the central sulci along the flagellum were observed. The remaining sensilla were randomly distributed on the antenna, mainly at the ventral surface, while the dorsal surface was almost totally covered by scales. This is the first report about ultrastructural morphology of the antenna of A. monuste, whose sensilla appear similar to those of other Pieridae butterflies, suggesting mechanical, chemo-, thermo-, and hygro-sensitivity in this insect.

Dorsal setae in Raoiella (Acari: Tenuipalpidae): Their functional morphology and implication in fluid secretion.

The setae of mites are not regarded as secretory structures, yet in the flat mite genus Raoiella, each developmental stage presents droplets of fluid associated with the tips of their dorsal setae. To understand the origin of this fluid, the ultrastructure of the dorsal setae is investigated in females of Raoiella bauchani Beard & Ochoa and the invasive pest species Raoiella indica Hirst using scanning and transmission electron microscopy techniques. The dorsal setae are barbed along their entire length and have either a broadened plumose or a flat spatulate tip. Ultrastructurally, they present the typical features of mechanoreceptors, but have a "hollow" axis represented by a protoplasmatic core containing dendritic branches. This combination of ultrastructural characters indicates that the setae might be multimodal receptors: acting as both mechanoreceptors and contact chemoreceptors. The epidermal cells that underlie the setal sockets are columnar and have an ultrastructure that suggests they have a glandular function. Moreover, these cells present regular microvilli apically and form extracellular cuticular canals, containing epicuticular filaments, that are connected with the microvilli proximally and which open via pores onto the surface of the setal base distally. This arrangement indicates that the secretion from the microvilli passes into the canals and is then conducted to pores at the base of the seta, where it then accumulates and moves up the setal shaft, along the longitudinal grooves of the barbs. Based on similar arrangements in some insect taxa, the organization of the structures here observed in Raoiella suggests the passage of a non-polar, water insoluble, lipoid fluid through the cuticle, the function of which is still obscure.

Morphological characterization of antennal sensilla of Earias vittella (Fabricius) (Lepidoptera: Nolidae).

The shoot and fruit borer, Earias vittella Fab. (Lepidoptera: Nolidae) is an important and most devastating insect pest on okra and cotton. The pest mainly responsible for causing significant direct damage to tender shoots and fruits of okra, flowers and green bolls of cotton causing net yield loss in both crops. Many non-chemical control strategies have been developed under the insect pest management program, A complete knowledge on the antennal morphology of E. vitella is essential for future electrophysiological and behavioural studies. In the present study, the antennal morphology and types of sensilla on the antennae of both sexes of E. vitella were examined using light and scanning electron microscopy. Nine distinct types of sensilla were identified on the antennae of both sexes: sensilla trichodea, sensilla basiconica, sensilla coeloconica, sensilla auricillica (multiporous), sensilla chaetica, uniporous peg sensilla (uniporous), sensilla styloconica, sensilla squamiformia and bohm bristles (aporous). Among all sensilla, the most widespread are multiporous sensilla trichodea with 42.90 ± 1.77/flagellomere in male and 37.38 ± 1.38/flagellomere in female. Sensilla basiconica were the second most common sensillum type in male antennae with 15.67 ± 1.92/flagellomere. Other multiporous sensilla such as auricillica (11.90 ± 0.99) and coeloconica (4.57 ± 0.25) were significantly more abundant in female than in male antennae. Results of the study provide morphological evidence that E. vitella antennae possess microscopic cuticular structures that can play a role in perception of pheromones, plant odours and other chemical stimulants. This will open up opportunities to assess the possibility of using pheromones and plant-derived compounds for the monitoring or management of E. vittella moths in the agricultural landscapes.

Crucial role of framework with cytoskeletal actin filaments for shaping microstructure of footpad setae in the ladybird beetle, Harmonia axyridis.

Insects that can walk on smooth surfaces have specialized structures, footpads, on their legs. Footpads play an important role in adhesion to the substrate surface. Although the morphology and function of footpads have been studied, the mechanism of their formation is still elusive. In the ladybird beetle (Harmonia axyridis), hairy footpads are present on the first and second tarsal segments of the legs. The footpads are covered with hundreds of hairs, i.e. setae, whose tips consist of four types: pointed, lanceolate, spatular, and discoidal. We examined the formation of the footpad during the pupal stage using immuno-staining and fluorescent-conjugated phalloidin staining. We found that a seta was composed of a shaft and a socket and some setae were accompanied by a neuron. By the mid-pupal stages, the shaft cells elongated to form a setal structure. Cytoskeletal actin bundles ramified to create a framework for the setal tip structure of the cells. We examined the effects of the application of cytochalasin D, which inhibits actin polymerization, on the formation of footpad setal structures. The results showed that the setal tips were deformed by the inhibition of actin polymerization. Our observations reveal that cytoskeletal actin filaments are involved in shaping the setae.