Basiconic Sensilla Research Articles

Olfactory Sensory Neurons of the Asian Longhorned Beetle, Anoplophora glabripennis, Specifically Responsive to its two Aggregation-Sex Pheromone Components.

We performed single-sensillum recordings from male and female antennae of the Asian longhorned beetle, Anoplophora glabripennis, that included as stimuli the two components of this species' aggregation-sex pheromone in addition to various general odorants. We compared the aggregation-sex-pheromone-component responses of olfactory sensory neurons (OSNs) to those of OSNs that responded to a variety of plant-related odorants. In the smooth-tipped, tapered, trichoid sensilla on the most distal antennal flagellomeres nos. 10 or 11 of both males and females, we found OSNs with high-amplitude action potentials that were tuned to the aldehyde and alcohol pheromone components and that did not respond to various plant-related volatiles. Because this OSN type responded to both the alcohol and aldehyde components it cannot be considered to be specifically tuned to either component. These large-spiking OSNs were co-compartmentalized in these sensilla with a second, smaller-spiking OSN responding to plant-related volatiles such as geraniol, citronellal, limonene, 1-octanol, nerol and citral. The large-spiking OSNs thus appear to be a type that will be involved in aggregation-sex pheromone pathways targeting a specific glomerulus in the antennal lobe and in generating pheromone-related behavioral responses in A. glabripennis. In other sensilla located in these distal antennal flagellomeres as well as those located more proximally, i.e., mid-length along the antenna on flagellomere nos. 4-7, we found OSNs in blunt-tipped basiconic sensilla that were responsive to other plant-related volatiles, especially the terpenoids, (E,E)-alpha farnesene, (E)-β-farnesene, β-caryophyllene, and eugenol. Some of these terpenoids have been implicated in improving attraction to pheromone-baited traps. Some of these same OSNs responded additionally to either of the two sex pheromone components, but because these OSNs also responded to some of the above plant volatiles as shown by cross-adaptation experiments, these OSNs will not be the types that convey sex-pheromone-specific information to the antennal lobe.

Sensory organs of forensically important fly Ophyra capensis (Wiedemann, 1818) (Diptera: Muscidae): A scanning electron microscopic study

Dipterans, especially the sarcosaprophagous communities are of substantial importance from medical, veterinary and forensic entomological perspectives. Muscids are generally seen to colonize carcasses at advanced stages of decomposition when the initial dominance of calliphorids and sarcophagids subsides. Ophyra capensis (Wiedemann, 1818), a muscid fly with a relatively wide distribution range is considered of decent forensic relevance as it has been reported not only from cadavers placed outdoors but also from graves and exhumed corpses. The prime objective of the present study is to analyse and interpret the ultrastructural morphology of three sensory organs, namely, the ocellar region, compound eye and antenna of adult male and female Ophyra capensis with the help of scanning electron microscopy, so as to facilitate accurate morphological identification of the species in forensic entomological investigations. SEM analysis of the ocellar region revealed that it was larger in size in females and covered with microtrichia. Ultrastructural analysis of the compound eye indicated that the antero-frontally located ommatidia were larger in size in comparison to the rest of the facets, along with notable sexual dimorphism regarding the size of the ommatidia. The ultrastructure of the antenna displayed the presence of five types of sensilla, two types of chaetic sensilla on the scape and pedicel; trichoid sensilla and two types of basiconic sensilla on the flagellum along with numerous microtrichia. Both types of basiconic sensilla displayed a multiporous surface indicating their characteristic olfactory function. The morphological characteristics of these sensilla along with their probable functions are discussed in greater details.

A receptor-neuron correlate for the detection of attractive plant volatiles in Helicoverpa assulta (Lepidoptera: Noctuidae)

Plant volatiles are vital cues in the location of hosts for feeding and oviposition for Lepidoptera moths. The noctuid Helicoverpa assulta is a typical polyphagous moth, regarded as a good model for studying the olfactory reception of plant volatiles. In this study, four full-length genes encoding odorant receptors HassOR24, HassOR40, HassOR41, and HassOR55 expressed in antenna in H. assulta were functionally characterized. The highly expressed HassOR40 was narrowly tuned to a few structurally-related plant volatiles: geranyl acetate, geraniol and nerolidol. By systematically analyzing responses of single neuron in both trichoid sensilla and basiconic sensilla using single sensillum recording, the specific neuron B in one type of short trichoid sensilla was found to be mainly activated by the same chemicals as HassOR40 with high sensitivity, and with no significant difference between male and female neurons. Thus, a clear “receptor-neuron” relationship in H. assulta was demonstrated here, suggesting that HassOR40/HassOrco are expressed in neuron B of short trichoid sensilla. The active tobacco volatile nerolidol, recognized by this receptor-neuron line, elicits significant behavioral attraction of both sexes in H. assulta adults. The results indicate that we identified a receptor-neuron route for the peripheral coding of a behaviorally relevant host volatile in H. assulta.

Distribution and Ultrastructure of Sensilla onUlomoides dermestoides(Coleoptera: Tenebrionidae) Antennae1

Abstract Ulomoides dermestoides (Chevrolat) (Coleoptera, Tenebrionidae) is a storage pest and an insect of medical importance. Since this insect lives in the dark and does not emit sounds, its sensation of the external environment is based primarily on sensilla, so it could serve as an ideal model for the study of these structures. Scanning electron microscopy was used to identify the types of antennal sensilla of male and female U. dermestoides and to characterize the function of different types of sensilla observed. The bead-like antenna of U. dermestoides is composed of a scape (one segment), a pedicel (one segment), and a flagellum (nine segments). Six types of sensilla were observed on the antennae of both females and males: the sensilla trichoidea (subtypes I, II, and III), sensilla chaetica (subtypes I, II, and III), sensilla basiconica, basiconic mastoid sensillum, sensilla styloconica (subtypes I and II), and the Bohm bristle. The Student's t test was used to compare the distribution of these sen...

The Structure and Evolution of the Apical Sensory Zone Structures in the Maxillary and Labial Palps of Caddisflies (Trichoptera)

A comparative morphological study of the apical regions of palps in Trichoptera from different evolutionary lines of the order was carried out, and a comparison was made with representatives of Lepidoptera and Mecoptera. Light and scanning electron microscopy methods were used to study the structure of palpal apices in 81 species of the order Trichoptera, 6 of Lepidoptera, and 2 species of Mecoptera. As a result, 11 types of sensilla were identified on the terminal palpal segments, and highly differentiated apical sensory zones with thick short basiconic sensilla were found on the maxillary and labial palps. The presence of an apical sensory zone in caddisflies and related orders is recognized as a plesiomorphic character.

Differential morphology of the sensory sensilla of antennae, palpi, foretarsi and ovipositor of adult Tribolium castaneum (Herbst) (Coleoptera:Tenebrionidae)

The red flour beetle, Tribolium castaneum, is an invasive pest of a variety of stored products that is found in most tropical and subtropical countries. To further understanding of the mechanism of insect-host chemical communication, we examined the morphology, distribution and abundance of various sensilla associated with antennae, palpi, foretarsi and ovipositor by scanning electron microscopy. No sexual dimorphism was found between male and female antennae, palpi and foretarsi. In both sexes, four types of antennal sensilla were characterized: two subtypes of trichoid sensilla (st1-2), four subtypes of basiconic sensilla (bs1-4), multiporous grooved peg (mgp) and styloconica sensilla (sst). Overall, the olfactory and gustatory sensilla were clustered mainly on the three antennal club flagellomeres. The sensory field of both maxillary and labial palps was concentrated on the distal segment forming the chemosensory field. Three types of sensilla on both maxillary and labial palps were characterized: trichodea, basiconica, and two subtypes of sensilla styliconica. Maxillary palps carried higher numbers of all types of sensilla than labial palps. Two types of sensilla were characterized on the fore tarsi: trichoidea and cheatica. Only one type of sensilla was found on the ovipositor, trichodea. The functional roles of these sensilla are discussed in relation to their external structure and distribution. Further anatomical, physiological and behavioral studies on identifying the functional types of these sensilla and their role in the selection of an appropriate food source can provide a basis for the development of semiochemically based control strategies.

Antennal sensilla of Didesmococcus koreanus Borchsenius (Hemiptera: Coccoidea: Coccidae) in different instars

To better understand the morphology, structure and function of antennae and antennal sensilla of Didesmococcus koreanus Borchsenius, family Coccidae (Hemiptera: Coccoidea), in the first-instar nymph, adult female and adult male stages, we investigated these stages using light microscopy and scanning and transmission electron microscopy. The results show that the antennae of first-instar nymphs and adult females are similar in morphology and sensilla distribution. The antennae of first-instar nymphs comprise six segments, and each antenna has 24 sensilla of six types: one campaniform sensillum (Ca), eleven smooth aporous trichoid sensilla (St), two basiconic sensilla (Ba), five multiporous pegs (Mp), two smooth multiporous pegs (sMp) and three chaetica sensilla (Ch). The antennae of adult females have six or seven segments, and each antenna has 25 sensilla of the same six types as the first nymphs, but with twelve sensillum St. The antennae of adult males are more developed, and each antenna contains 155–213 sensilla of eight types: 16–34 St, 1 Ca, 2–5 Ba, 1 Johnston’s organ (Jo), 3 knob sensilla (Ks), 5 Mp, 2 sMp and 120–181 multiporous sensilla trichodea (Mt). Based on our analysis, we discuss the possible functions of the antennae and antennal sensilla of D. koreanus in different instars.

Typology and distribution of antennal sensory organs of adults Haematobia irritans of the Midwest Region of Brazil

ABSTRACT: Considering the great economic and sanitarian importance of Haematobia irritans − the development of resistance of this species to the main chemical insecticides used in its control, in several other localities of the world; as well as that different strains of the same species frequently present different types and distribution patterns −, the present aim study was to investigate the typology and distribution of different types of sensillae of H. irritans adults, from populations of this fly present in Brazilian Midwest, with emphasis on olfactory sensillae. This study provides new data on the typology and sensillary distribution of antennal sensilla of this fly. In the antennal segments were found non-innervated spinules and ten subtypes of sensilla: long bristles sensillum, long basiconic sensillum, blunt coeloconic sensillum, clavate coeloconic sensilla − single-tip and double-tip subtypes −, grooved coeloconic sensillum, long grooved coeloconic sensillum, trichoid sensillum, coeloconic sensillum, and smaller basiconic sensillum. A slight sexual dimorphism was observed in the antennal sensillae of H. irritans. These results provide a morphological basis for future investigations on olfactory-mediated behavior of this species, and could assist future studies for the development of alternative measures to the monitoring and control of this fly populations, with less environmental impact.

Distribution of sensory sensilla in the labral food canal and cibarium of Chrysops exitans (Diptera: Tabanidae).

Sensilla, beginning at the distal-most tip of the labrum and extending proximally through the cibarium to the stomodaeum, were examined in females of Chrysops exitans Walker. Totals of 328 setiform sensilla (range, 14 to 21; mean = 18.2; ±1 SD = 1.67), and 36 basiconic sensilla (mean = 2.0; ±1 SD = 0) were observed in the food canal of n = 18 sample individuals. Both types of sensilla were aggregated distally in the canal. Additionally, a group of five to 10 sensilla was observed in each lateral wall of the epipharynx, with a single median group, consisting of both setiform and basiconic sensilla, positioned immediately distal to the mouth opening into the cibarium. Two pairs of basiconic sensilla were consistently observed in the stomodaeum of every fly.

Comparative exploration of antennae in Pseudopontia, and antennal clubs of the tribes Leptideini and Dismorphiini (Lepidoptera: Pieridae).

We examined antennal ultrastructure in species of Dismorphiinae and Pseudopontiinae (Pieridae) using scanning electron microscopy (SEM). We examined two species of Pseudopontia (Pseudopontiinae) and more than 30 species in seven genera of two tribes in the subfamily Dismorphiinae: Leptidea, Enantia, Pseudopieris, Lieinix, Moschoneura, Dismorphia, and Patia. We focused on the scaleless terminal area of the antenna where there are many types of sensilla, some of which are clustered together and constitute specialized organs. We measured, described, and illustrate at different magnifications structures including the antennal club, antennomeres, sulci, pseudosulci, and chaetic, trichoid, coeloconic, basiconic, and auriculate sensilla, as well as other previously unnamed sensilla. From these antennal features, we created a matrix of characters that allowed us to recognize divergence between the tribes Leptideini and Dismorphiini. The antennae of Leptideini have fewer scaleless antennomeres in the antennal club than those of Dismorphiini, a greater number of pseudosulci disaggregated or dispersed (in Leptidea), and fewer types of sensilla and microtrichia (a more homogeneous antennal morphology), as well as a reduction in the density of sensilla. In Leptidea the antennal form is more specialized: it is shorter in comparison to genera of other Papilionoidea families. We also created a matrix of general morphological characters of Dismorphiinae and Pieridae from the taxonomic literature. This matrix confirms the marked character divergence between the tribes and allows for a more meaningful discussion regarding the relationships between Dismorphiinae and the other subfamilies of Pieridae (i.e., Pseudopontiinae, Coliadinae, and Pierinae). We argue that Pseudopontiinae cannot be considered the least derived subfamily among Pieridae because pupal features, wing venation, and antennal characters exhibit a combination of primitive and specialized states. In addition, we discuss our results from the perspective of patterns of food plant usage in pierid subfamilies, specifically the diversification of several Dismorphiinae genera on Hologalegina and Ingeae (Fabaceae).

Comparison of the antennal sensilla of females of four fig-wasps associated with Ficus auriculata

A comparison was performed of the antennal sensilla of females of four chalcid wasp species Ceratosolen emarginatus Mayr, 1906, Sycophaga sp., Philotrypesis longicaudata Mayr, 1906, and Sycoscapter roxburghi Joseph, 1957, which are specific and obligatory associated with Ficus auriculata (Lour, 1790). The four species exhibit different oviposition strategies in the fig ovules where their offspring hatch and develop. Antennal sensilla morphology was evaluated using scanning electron microscopy. Females of the four species present 11 morphologically similar types of sensilla: trichoid sensilla, sensilla obscura, chaetica sensilla 1 and 2, which all have mechanosensory functions; uniporous basiconic sensilla, which are presumably contact chemosensilla; basiconic capitate peg sensilla, coeloconic sensilla 1, multiporous basiconic and placoid sensilla, which may be regarded as olfactory sensilla, and coeloconic sensilla 2 and 3, which are presumed to be proprioreceptors or pressure receptors. The four species have significant differences in the abundance and arrangement of trichoid sensilla and chaetica sensilla 1 on the flagellum. The coeloconic sensilla and sensilla obscura only occur on the antennae of C. emarginatus that enter figs. The chemosensilla which are presumably involved in host discrimination, i.e., basiconic sensilla, multiporous placoid sensilla and basiconic capitate peg sensilla, are similar in shape and configuration, although they present some differences in abundance. These findings provide practical information on the adaptations of fig wasps and the relationship between multisensory antennae and functions in fig wasp behaviour.

Neofunctionalization of \u201cJuvenile Hormone Esterase Duplication\u201d in Drosophila as an odorant-degrading enzyme towards food odorants

Odorant degrading enzymes (ODEs) are thought to be responsible, at least in part, for olfactory signal termination in the chemosensory system by rapid degradation of odorants in the vicinity of the receptors. A carboxylesterase, specifically expressed in Drosophila antennae, called “juvenile hormone esterase duplication (JHEdup)” has been previously reported to hydrolyse different fruit esters in vitro. Here we functionally characterize JHEdup in vivo. We show that the jhedup gene is highly expressed in large basiconic sensilla that have been reported to detect several food esters. An electrophysiological analysis demonstrates that ab1A olfactory neurons of jhedup mutant flies exhibit an increased response to certain food acetates. Furthermore, mutant flies show a higher sensitivity towards the same odorants in behavioural assays. A phylogenetic analysis reveals that jhedup arose as a duplication of the juvenile hormone esterase gene during the evolution of Diptera, most likely in the ancestor of Schizophora, and has been conserved in all the 12 sequenced Drosophila species. Jhedup exhibits also an olfactory-predominant expression pattern in other Drosophila species. Our results support the implication of JHEdup in the degradation of food odorants in D. melanogaster and propose a neofunctionalization of this enzyme as a bona fide ODE in Drosophilids.

Taste input from tarsal sensilla is related to egg‐laying behavior in Papilio hospiton

AbstractIn herbivorous insects, host selection involves various sensory modalities (sight, smell, taste), but the contact chemoreceptors capable of detecting stimuli both from host and non‐host plants play an important role in the final steps of oviposition behavior. Female butterflies scratch and drum the leaf surface and taste the compounds present in plant saps with their tarsal chemosensilla. We assumed that tarsal taste sensitivity may be related to the breadth of host selection in ovipositing females of Papilio hospitonGéné (Lepidoptera: Papilionidae). The spike activity of tarsal taste basiconic sensilla was recorded in response to stimulation with NaCl, bitter compounds, and carbohydrates, with the aim of characterizing the gustatory receptor neurons (GRNs) and of comparing the response patterns in the light of differences in acceptability of host plants. Then we studied the sensitivity of GRNs to saps of the host plants Ferula communis L., Peucedanum paniculatumLoisel, Pastinaca latifolia (Duby) DC. (all Apiaceae), and Ruta lamarmorae Bacch., Brullo et Giusso (Rutaceae), and evaluated the relationship between taste sensitivity and oviposition preference. The results indicate that (1) each sensillum houses sugar‐, bitter‐, and salt‐sensitive cells; (2) the spike activity of the gustatory neurons in response to plant saps produces a different response pattern across all active GRNs; and (3) the number of eggs laid on each plant is highest on F. communis and lowest on R. lamarmorae. These results suggest that the varying activity of the tarsal GRNs may affect host plant acceptability and that ovipositing females of P. hospiton seem to be able to discriminate between host plants.

Structure of antennal sensilla in the caddisfly genus Rhyacophila pictet (Trichoptera, Rhyacophilidae)

Microstructure and distribution of sensilla were studied in 25 species of caddisflies of the family Rhyacophilidae for the first time. Comparative analysis allowed 13 sensilla types to be identified in members of this family: long grooved trichoid, curved trichoid, chaetoid, mushroom-like pseudoplacoid, forked pseudoplacoid, leaf-like pseudoplacoid, dissected pseudoplacoid, multiforked pseudoplacoid, styloconic, auricillic, coronal, basiconic sensilla, and Bohm’s bristles. The largest variations were found in the pseudoplacoid sensilla. Dissected, leaflike, auricillic, and multiforked sensilla were discovered in the order Trichoptera for the first time. Curved trichoid sensilla can be grouped or assembled into sensory fields. The total number of sensilla per antennal segment decreases towards the antenna apex. Data on the structural diversity of sensilla in groups of fast-evolving species suggest the participation of sensilla structures in the speciation processes.

Ovipositor setation in oldest insects (Insecta: Archaeognatha) revealed by SEM and He-ion microscopy

Archaeognatha represent the oldest living lineage of true insects (=Ectognatha), which are remarkable, among others, for plesiomorphic genital morphology and complicated mating behaviour. I used scanning electron microscopy and He-ion microscopy to examine the ovipositor morphology of seven species, in order to describe the cuticle microsculpture. The species studied are characterised by different types of the ovipositor setation pattern, which are considered an important taxonomic feature for Archaeognatha. The common and well discernible elements of ovipositor setation in Archaeognatha are: (1) non-articulated terminal seta, (2) grooved type I basiconic sensillum with apical pore, (3) multiporous type II basiconic sensillum, (4) articulated setae of different length. Coeloconica-like sensilla and campaniform sensilla demonstrate a variety of transient morphology. Results of this study provide morphological evidence of presence of olfactory receptors on the ovipositor in Archaeognatha. The possible functions of the ovipositor setation in Archaeognatha are discussed.

Chemosensory sensitivity reflects reproductive status in the ant Harpegnathos saltator

Insects communicate with pheromones using sensitive antennal sensilla. Although trace amounts of pheromones can be detected by many insects, context-dependent increased costs of high sensitivity might lead to plasticity in sensillum responsiveness. We have functionally characterized basiconic sensilla of the ant Harpegnathos saltator for responses to general odors in comparison to cuticular hydrocarbons which can act as fertility signals emitted by the principal reproductive(s) of a colony to inhibit reproduction by worker colony members. When released from inhibition workers may become reproductive gamergates. We observed plasticity in olfactory sensitivity after transition to reproductive status with significant reductions in electrophysiological responses to several long-chained cuticular hydrocarbons. Although gamergates lived on average five times longer than non-reproductive workers, the shift to reproductive status rather than age differences matched the pattern of changes in olfactory sensitivity. Decreasing sensillum responsiveness to cuticular hydrocarbons could potentially reduce mutually inhibitory or self-inhibitory effects on gamergate reproduction.

Hornets Have It: A Conserved Olfactory Subsystem for Social Recognition in Hymenoptera?

Eusocial Hymenoptera colonies are characterized by the presence of altruistic individuals, which rear their siblings instead of their own offspring. In the course of evolution, such sterile castes are thought to have emerged through the process of kin selection, altruistic traits being transmitted to following generation if they benefit relatives. By allowing kinship recognition, the detection of cuticular hydrocarbons (CHCs) might be instrumental for kin selection. In carpenter ants, a female-specific olfactory subsystem processes CHC information through antennal detection by basiconic sensilla. It is still unclear if other families of eusocial Hymenoptera use the same subsystem for sensing CHCs. Here, we examined the existence of such a subsystem in Vespidae (using the hornet Vespa velutina), a family in which eusociality emerged independently of ants. The antennae of both males and female hornets contain large basiconic sensilla. Sensory neurons from the large basiconic sensilla exclusively project to a conspicuous cluster of small glomeruli in the antennal lobe, with anatomical and immunoreactive features that are strikingly similar to those of the ant CHC-sensitive subsystem. Extracellular electrophysiological recordings further show that sensory neurons within hornet basiconic sensilla preferentially respond to CHCs. Although this subsystem is not female-specific in hornets, the observed similarities with the olfactory system of ants are striking. They suggest that the basiconic sensilla subsystem could be an ancestral trait, which may have played a key role in the advent of eusociality in these hymenopteran families by allowing kin recognition and the production of altruistic behaviors toward relatives.

Putative Sensory Structures Associated with the Food Canal of Hybomitra difficilis (Diptera: Tabanidae).

The feeding tube of Hybomitra difficilis is made up of a short distal vestibule followed by a food canal that leads to the cibarium; the two regions demarcated by the vestibule/food canal junction. Two pairs of sensilla were consistently observed in the vestibular walls, the first pair of basiconic design in the mid-vestibular region, and the latter pair of setiform design at the base of the vestibule. Numbers of setiform sensilla in the food canal varied from 31 to 69 (mean = 48.15; ± 1 SD = 10.02), and were aggregated in the distal and distal median regions of the food canal. This aggregation was significant (X 2 = 241.49; P < 0.0001), leading to rejection of the null hypothesis that setiform sensilla were evenly distributed throughout the length of the food canal.Two basiconic sensilla were observed in the food canal of every fly examined. While basiconic sensilla varied in position (i.e., distance) from the vestibule/food canal junction, they were significantly aggregated (X 2 = 14.42; P < 0.0024) in the two median sections of the distal canal region, thus leading to the rejection of Ho that basiconic sensilla were evenly distributed in subdivisions (i.e., sections) of the distal canal region.

Scanning electron microscopic studies on antenna of Hemipyrellia ligurriens (Wiedemann, 1830) (Diptera: Calliphoridae)—A blow fly species of forensic importance

Blow flies (Diptera: Calliphoridae) are one of the foremost organisms amongst forensic insects to colonize corpses shortly after death, thus are of immense importance in the domain of forensic entomology. The blow fly Hemipyrellia ligurriens (Wiedemann, 1830) (Diptera: Calliphoridae) is considered as a forensically important fly species globally and is also known for its medical and veterinary importance. In the present study, we report for the first time scanning electron microscopic studies on the morphology of sensilla of antenna of adult male and female of H. ligurriens is with profound importance in better understanding of the insect morphology from forensic entomological perspective, and also could aid in proper identification of the species from other calliphorid flies. The structural peculiarities observed in the (i) antenna of H. ligurriens with three segments- scape, pedicel and flagellum with dorso-laterally placed arista (ii) densely covered microtrichia and most abundant trichoid sensilla identified on the antenna (iii) observation of only one type of sensilla, chaetic sensilla (ChI) on the scape (iv) two types of chaetic sensilla (ChI and ChII) and styloconic sensilla on the pedicel (v) the flagellum with three types of sensilla- trichoid, basiconic and coeloconic sensilla (vi) Basiconic sensilla with multiporous surfaces with characteristic olfactory function. Moderate sexual dimorphism in the width of the flagellum, the females with wider flagella than the males, bear significance to the fact that they bear more multi-porous sensilla than the males, thus suffice their need to detect oviposition sites. Significant difference was observed in the length and width of coeloconic sensilla between the two sexes, the females showed bigger coeloconic sensilla, suggesting their function in oviposition site detection and successful colonization in corpses.

Chemosensory Responses to the Repellent Nepeta Essential Oil and Its Major Component Nepetalactone by Aedes aegypti (Diptera: Culicidae), a Vector of Zika Virus.

Nepeta essential oil (Neo; catnip) and its major component, nepetalactone, have long been known to repel insects including mosquitoes. However, the neural mechanisms through which these repellents are detected by mosquitoes, including the yellow fever mosquito Aedes aegypti (L.), an important vector of Zika virus, were poorly understood. Here we show that Neo volatiles activate olfactory receptor neurons within the basiconic sensilla on the maxillary palps of female Ae. aegypti. A gustatory receptor neuron sensitive to the feeding deterrent quinine and housed within sensilla on the labella of females was activated by both Neo and nepetalactone. Activity of a second gustatory receptor neuron sensitive to the feeding stimulant sucrose was suppressed by both repellents. Our results provide neural pathways for the reported spatial repellency and feeding deterrence of these repellents. A better understanding of the neural input through which female mosquitoes make decisions to feed will facilitate design of new repellents and management strategies involving their use.