Antennal Morphology Research Articles

Chaetotaxy of the fourth larval stage of Pintomyia longiflocosa, a primary vector of cutaneous leishmaniasis in Colombia.

Pintomyia (Pifanomyia) longiflocosa is an endemic species from Colombia, found between the central and eastern Andes, and reported as one of the primary vectors of cutaneous leishmaniasis in coffee-growing zones of the country. This species is classified in the Townsendi series and can only be identified by the morphology of the male adults. To determine the potential use of the fourth larval stage of the vector Pi. longiflocosa in morphological taxonomy based on the description of its chaetotaxy. Pintomyia longiflocosa adults were captured in Campoalegre, Huila, and reared in the Entomology Laboratory at the Colombian Instituto Nacional de Salud. To identify the setae found in each corporal segment, 15 fourth-instar larvae were mounted on microscope slides using Canadian balm after being cleared with 10 % potassium hydroxide and saturated phenol. Additionally, five specimens were prepared for their observation by scanning electron microscopy. Based on the description of Pi. longiflocosa, we established that all species of the subgenus Pifanomyia so far described have the same antennal morphology and clavate setae along their body. However, various setae present in Pi. longiflocosa are absent in Pi. youngi, suggesting differences among the larvae of the Townsendi series. These results support the potential importance of morphological characters from the fourth larval instar, such as antennal morphology and chaetotaxy, specifically in closely related species that are cryptic in their adult stages.

Revision of the polyphyletic genus Hirrius Bolívar, 1887 (Orthoptera: Tetrigidae), with descriptions of three new genera and insights into antennal sensilla morphology

Discotettiginae were recently synonymized with Scelimeninae, but the polyphyletic genus Hirrius Bolívar, 1887, with five species endemic to the Philippines and Sulawesi, remained an unsolved issue. Besides similarly widened subapical antennomeres, head and pronotum, other traits suggest that Hirrius members belong to different subfamilies. The genus is now split into four genera, with four new species. Hirrius (Tetrigidae: incertae sedis) now includes three species, one of which is new, all endemic to Mindanao, the Philippines: H. punctatus (Stål 1877), H. mindanaensis (Günther, 1938), and H. ruber Skejo, Patano et Kasalo sp. nov. A lectotype is designated for H. punctatus, because the type series was found to contain two different species belonging to two different genera. Three new genera are described. Genus Parahirrius Skejo, Patano et Kasalo gen. nov. (Tetrigidae: incertae sedis) consists of P. parvus Skejo, Patano et Kasalo sp. nov. and P. amorosus Skejo, Patano et Kasalo sp. nov., both endemic to Mindanao. Genus Zvierckia Skejo, Tumbrinck et Pushkar gen. nov. (Scelimeninae: Discotettigini) includes Z. montana (Günther, 1937), comb. nov., Z. sarasinorum (Günther, 1937), comb nov., and Z. storozhenkoi Skejo et Tumbrinck sp. nov., all endemic to Sulawesi. Genus Guentheracris Skejo, Tumbrinck et Pushkar gen. nov. (Tetrigidae: “Asian Metrodorinae”) includes G. scrobiculata (Günther, 1937), comb. nov. from Sulawesi. Subapical antennomeres of Zvierckia storozhenkoi sp. nov. and Phaesticus mellerborgi (Stål, 1855) were scanned for the first time and compared to Discotettix belzebuth (Serville, 1838). Zvierckia gen. nov. and Discotettix Costa, 1864, both Scelimeninae: Discotettigini members, share many features of the antennal morphology, such as many basiconic sensilla on the antennal margins giving the ridge a saw-like impression. On the other hand, antennae of Phaesticus Uvarov, 1940 contain many elongated placoid sensilla, which are fully absent in the subapical widened segments of Zvierckia gen. nov. and Discotettix.

Morph-linked variation in female pheromone signalling and male response in a polymorphic moth.

Understanding the maintenance of genetic variation in reproductive strategies and polymorphisms in the wild requires a comprehensive examination of the complex interactions between genetic basis, behaviour and environmental factors. We tested the association between three colour genotypes and variation in female pheromone signalling and male antennal morphology in the wood tiger moth (Arctia plantaginis). These moths have genetically determined white (WW, Wy) and yellow (yy) hindwings that are linked to mating success and fitness, with heterozygotes (Wy) having an advantage. We hypothesized that attractiveness and reproductive success are correlated, with Wy females being more attractive than the other two genotypes which could contribute to maintaining the polymorphism. Female attractiveness was tested by baiting traps with females of the three colour genotypes both in low- (i.e. field set-up) and in high-population density (i.e. large enclosure set-up). Male's ability to reach females was correlated to their own colour genotype and antennal morphology (length, area and lamellae count). Contrary to our prediction, morph-related reproductive success and attractiveness were not correlated. Heavier Wy females attracted a lower proportion of males compared to WW and yy females. Specifically, an increase in weight corresponded to a decreased Wy but increased yy female attractiveness. yy females were generally more attractive than others likely due to earlier pheromone release. In males, lamellae count and genetic colour morph were linked to the male's ability to locate females. Furthermore, male traits affected their ability to reach females in a context-specific way. Males with denser antennae (i.e. higher lamellae count) and white males reached the females faster than yellows in the enclosure, while yellow males located females faster than whites in the field. Our results indicate that higher yy female attractiveness was likely affected by the combined effect of early pheromone release, female weight and higher population density. Males' searching success was affected by morph-specific behavioural strategies and local population density. Ultimately, the combined effect of genotype-related pheromone signalling strategies of females together with environment-dependent male behaviour affect male response and potentially contribute to maintaining variation in fitness-related traits.

Identification of chemosensory genes and antennal sensilla in Nassophasis sp. (Coleoptera: Rhynchophorinae)

Phytophagous insects rely on plant volatiles to select and locate hosts for feeding or reproduction and their olfactory system is essential for detecting plant volatiles. The stem-boring pest, Nassophasis sp. damages Dendrobium and causes economic losses. Currently, there are no effective methods for its control. However, understanding the morphological and molecular basis of its olfactory system may identify new pathways for their management and control. In this study, we observed the stemborer's antennal sensilla using scanning electron microscopy, and transcriptome sequencing was undertaken to annotate and analyze its chemosensory genes. Results showed that the antennal morphology is similar between males and females, with five types of antennal sensilla observed: sensilla chaetica (SC), sensilla trichodea (ST), sensilla brush (SB), sensilla basiconica (SBA) and sensilla gemmiformium (SG). Sexual dimorphism was not observed in sensilla type, but in the length of SBA and SG. A total of 70 olfactory-related genes were annotated, including 16 odorant binding proteins (OBP), 5 chemosensory proteins (CSPs), 26 olfactory receptors (ORs), 9 gustatory receptors (GRs), 10 ionotropic receptors (IRs), and 4 sensory neuron membrane proteins (SNMPs). Most genes were highly expressed and 14 of these genes were only expressed in the head, and 7 genes in the abdomen. This study provides a theoretical basis for the olfactory perception of Nassophasis sp. and a scientific basis for developing new pest control strategies.

Taxonomic review of the genus Aldrichiopa Guimares, 1971 (Diptera: Tachinidae) with notes on antennal morphology and description of a new species.

A redescription of the genus Aldrichiopa Aldrich, 1934 (Diptera: Tachinidae) is provided and a new species, Aldrichiopa serrata Torres-Domnguez & Mulieri sp. nov. is described from specimens collected in Argentina and Chile. A detailed morphological description of the egg, first instar larva, and adult male and female including terminalia are presented for the first time. Exhaustive photographic records, scanning electron microscopy images, morphological detail of antennal ultrastructure, and updated geographic distributions are provided for the two species of the genus, Aldrichiopa coracella (Aldrich) and A. serrata sp. nov. An identification key based on males is provided. The taxonomic placement of Aldrichiopa to subfamily and tribe is discussed and information on the hosts of this genus of small tachinid flies is compiled.

New fossil genus and species of Yuripopovinidae (Insecta: Heteroptera, Coreoidea) from the Lower Cretaceous Jinju Formation, South Korea, with insights into the evolution of exaggerated antennae in the family

A new genus and species of Yuripopovinidae, Jinjupopovina eosahwae gen. et sp. nov. is described based on a piece of fragmentary fossil specimen from the lower Cretaceous Jinju Formation in Jinju City, South Korea. This species is the first record of Yuripopovinidae and the only heteropteran whose taxonomic status is reliably identified from the stratigraphic layer. Its antennal morphology provides a rare example of simultaneous enlargement in length and width among Heteroptera. Advantages and disadvantages of this antennal modification are discussed with references of other fossil and extant coreoids whose antennae are exaggerated. Our findings suggest that the antennae of Jinjupopovina facilitated visual signaling among infra-specific individuals or between reproductive partners. Evolutionary trends of the antennae in Yuripopovinidae are discussed with insights from Jinjupopovina.

The structure and morphogenic changes of antennae of Spilococcus alhagi (Hall) (Hemiptera: Coccoidea: Pseudococcidae) in different instars

To better understand the antennal morphology and sensilla distribution of Spilococcus alhagi (Hall) in different instars, the antennae are examined using light microscopy and scanning electron microscopy. The results show that the antennae of S. alhagi could be differentiated in different instars based on their stucture, number of flagellomere, and sensillar distribution. Functional antennae of S. alhagi appear in first instar nymphs, adult females, and adult males as many scale insects. The antennae of first-instar nymphs comprise six segments, and each antenna has 62–71 sensilla of eight types, including sensilla basiconica (SB), one type of sensilla trichoidea (ST1), two types of sensilla companiform (SCa, sSCa), two types of sensilla coeloconica (SCo1, SCo2) and two types of sensilla chaetica (SCh1, SCh2). The antennae of adult females have eight segments, but each antenna has 164–188 sensilla of the same eight types as the first instar nymphs. The antennae of adult males are more developed, and each antenna contains ten segments and 670–725 sensilla of eleven types, including knobbed seta sensilla (Ks), intersegmental sensilla (Ins), two types of sensilla trichoidea (ST1, ST2), two types of sensilla companiform (SCa, sSCa), two types of sensilla coeloconica (SCo1, SCo2) and three types of sensilla chaetica (SCh1, SCh2, bSCh). Of these, four types of sensilla, viz., Ks, ST2, Ins, bSCh are only observed on the antennae of adult males. The prepupa-like and pupa-like male nymphs both possess simplified antennae, and exhibit four types of sensilla (ST1, SCa, SCh1, SCh2). Based on these results, the morphogenic changes and potential functions of antennae of S. alhagi in different instars are discussed.

New Species of Paussus, Subgenus Scaphipaussus (Coleoptera: Carabidae: Paussinae), from Southeast Asia Reveal Ambiguities in Species Group Limits and High Species Diversity in the Oriental Region.

Paussus, commonly known as ant nest beetles, is the most diverse genus of Paussinae (Coleoptera: Carabidae) with a very complex taxonomic history. Biodiversity research in Southeast and South Asia yields new species that can contribute to a better understanding of the morphological disparity and species-group or subgenus delimitation. Here, we describe nine new species from Southeast Asia and China: Paussus (Scaphipaussus) fencli sp. nov. (China), P. (S.) mawdsleyi sp. nov. (Borneo), P. (S.) bakeri sp. nov. (Philippines), P. (S.) jendeki sp. nov. (Laos), P. (S.) saueri sp. nov. (India), P. (S.) annamensis sp. nov. (Vietnam), P. (S.) phoupanensis sp. nov. (Laos, Vietnam), P. (S.) bilyi sp. nov. (Thailand), and P. (S.) haucki sp. nov. (Thailand). We also bring new data on P. (S.) corporaali Reichensperger, 1927 (Java) and P. (S.) madurensis Wasmann, 1913 (India). Besides formal descriptions, we provide photographs of the habitus in the dorsal and dorsolateral view, antennal club, head crest, and male genitalia if the male is available. Based on the comparison of new and earlier described species, we show that the antennae are highly diverse within the Scaphipaussus. Considering other characters, some species are placed in Scaphipaussus, but they differ from putative relatives in the antennal morphology. The presence of the frontal protuberances and crests is a more reliable character. Additional species show that Scaphipaussus is most diverse in southeastern Asia, especially in Indo-Burma. Concerning its supposed late Miocene origin, the group underwent rapid radiation. The species diversity of Scaphipaussus almost doubled in the last decade, and it is highly probable that further species will be described in the future.

Morphology and Distribution of Antennal Sensilla on Spodoptera frugiperda (Lepidoptera: Noctuidae) Larvae and Adults

The invasive pest, Spodoptera frugiperda, commonly known as the fall armyworm (FAW), is a serious threat to food security in multiple countries worldwide. Insects’ antennal sensilla play a crucial role in perceiving plant odors and communication between male and female insects. This study aimed to examine the antennal morphology and sensilla variations on the antennae of FAW larvae and adults through scanning electron microscope analysis. The results revealed that third and fifth instar larval antennae possessed smell pores, sensilla pegs, and five types of antennal sensilla, namely sensilla trichodea, sensilla basiconica, sensilla chaetica, sensilla campaniform, and sensilla styloconicum, and the smell pores were first observed in Lepidoptera larvae. Furthermore, the size of sensilla in fifth instar larvae was significantly greater than those in third instar. On the adult antennae, there were smell pores and 12 types of sensilla identified: sensilla trichodea, sensilla basicaonica, sensilla auricillica, sensilla cavity, sensilla placodea, sensilla ligulate, Böhm’s bristles, sensilla chaetica, sensilla squamous, sensilla coeloconica, sensilla styloconicum, and sensilla uniporous peg. Notably, the sensilla cavity, sensilla placodea, sensilla ligulate, sensilla uniporous peg, and smell pores were first discovered in FAW adults. Compared with larvae, FAW adults have more types and amounts of sensilla. Additionally, we also discussed the possible functions of these antennal sensilla. This study provides valuable information for a comprehensive understanding of the type and function of antennal sensilla in FAW and assists in the development of novel pest control strategies, such as pest behavior control technology, for the prevention of this invasive pest.

Species of Paraclius Loew (Diptera: Dolichopodidae) with bi-lamellate antennal stylus: new combination, new synonym, and two new species

The species of Paraclius Loew with bi-lamellate arista-like stylus are revised and P. americanus (Schiner, 1868) comb. nov. is transferred from Tachytrechus Haliday and regarded as the senior synonym of P. diplacocerus Capellari, 2013 syn. nov. In addition, two new species with similar antennal morphology are described and illustrated from Brazil: P. bilamellatus sp. nov. (States of Espírito Santo and Goiás) and P. vulcanoae sp. nov. (State of São Paulo). A distribution map and a key to the males of known species of Paraclius with bi-lamellate arista-stylus are provided.

Antennal Sensilla in Longhorn Beetles (Coleoptera: Cerambycidae)

AbstractInsect antennae are crucial sensory organs that house numerous sensilla with receptors for perceiving a wide variety of cues dominating their world. Historically, inconsistent terminology and criteria have been used to classify antennal sensilla, which has greatly impeded the comparison of data even across closely related species. Longhorn beetles (Coleoptera: Cerambycidae) are no exception to this quandary, and despite their prominent antennae, few studies have investigated their antennal morphology and ultrastructure, and none have compared sensillar diversity and variation among cerambycids. Existing studies of longhorn beetle antennal sensilla include only 29 species in five of the eight cerambycid subfamilies and include misidentified sensilla types and conflicting terminology. As such, it is very difficult to conduct comparative morphological studies of antennal sensilla in longhorn beetles and challenging to understand inter- and intra-specific variation in the sensory systems of these beetles. To facilitate future comparative studies, we reviewed all accessible published papers that have used scanning and transmission electron microscopy (SEM and TEM) to investigate antennal sensilla in cerambycids, and present a first attempt at standardizing the classification of their documented sensilla types and subtypes. Specifically, we discuss seven major types of antennal sensilla (Böhm bristles, sensilla chaetica, chemosensory hairs, sensilla basiconica, dome shaped organs, sensilla coeloconica, and sensilla auricillica). We also imaged the antennae of relevant species of longhorn beetles using SEM and included images exemplifying as many of the sensilla types and subtypes as possible.

Reevaluation of the Subgeneric Classification of the North American Species of Prionus Geoffroy (Coleoptera: Cerambycidae: Prioninae: Prionini), with a Revision of the Subgenus Neopolyarthron Semenov and Notes on Prionus (Antennalia) Fissicornis Haldeman and Prionus (Prionus) Californicus Motschulsk

The classification of North American species of Prionus (Prionus) Geoffroy, sensu lato, is reevaluated based on male antennal morphology, with three subgenera being recognized: P. (Prionus), consisting of P. aztecus Casey, P. californicus Motschulsky, P. evoluticornis Komiya & Nogueira, P. flohri Bates, P. heroicus Semenov, P. howdeni Chemsak, P. laticollis (Drury), P. lecontei Lameere, P. mexicanus Bates, P. pocularis Dalman, and P. poultoni Lameere; P. (Antennalia) Casey, revived status, consisting of P. fissicornis Haldeman; and P. (Neopolyarthron) Semenov, revived status. The species of P. (Neopolyarthron) are revised and consist of P. imbricornis (Linnaeus), P. debilis Casey, revived status, and P. cuneatus Casey, revived status, with the latter two species being removed from synonymy with P. imbricornis. Prionus robustus Casey, new synonymy, is transferred from synonymy with P. imbricornis to synonymy with P. cuneatus. Prionus fissicornis parviceps Casey, revised synonymy, is removed from synonymy with P. imbricornis and returned to synonymy with P. fissicornis. A lectotype is designated for Cerambyx imbricornis Linnaeus. Keys to North American subgenera of Prionus and to species of P. (Neopolyarthron) are provided. The species of P. (Neopolyarthron) are redescribed, diagnosed, and illustrated, with the female of P. debilis being illustrated for the first time. A county-level distribution map is provided for each species of P. (Neopolyarthron) along with a detailed discussion of distribution, host records, habitat, and conservation status. Prionus imbricornis is associated with forested habitats, P. debilis is associated with tallgrass prairies, and P. cuneatus is associated with prairies and other grasslands. Prionus fissicornis is diagnosed from species of P. (Neopolyarthron), and the type specimens of P. (Antennalia) fissicornis parviceps Casey, P. (Antennalia) fissicornis transversus Casey, and P. (Antennalia) thoracicus Casey are reviewed and illustrated. The date of publication for P. fissicornis is corrected from 1846 to 1847. The following new state records are provided: for P. imbricornis: Delaware and New Jersey; for P. debilis: Minnesota; and for P. cuneatus: Alabama, Arkansas, Colorado, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Louisiana, Minnesota, Mississippi, Missouri, Montana, Nebraska, North Dakota, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, Wisconsin, and Wyoming. The following previously published country, state, and provincial records are considered to be in error and are removed from the distribution of the relevant species: for P. imbricornis: Canada (Ontario), Croatia, Dominican Republic, Germany, Haiti, Colorado, Connecticut, Iowa, Massachusetts, Minnesota, Montana, Nebraska, New Hampshire, New Mexico, North Dakota, Rhode Island, South Dakota, and Wisconsin; for P. debilis: Florida, Mississippi, North Carolina, North Dakota, Ohio, South Dakota, and Texas; for P. fissicornis: Ontario, Georgia, Louisiana, North Carolina, Pennsylvania, and South Carolina; and for P. californicus: Arkansas and Georgia.

Insights into the Antennal Characteristics and Olfactory Strategy of the Endangered Rhino Stomach Bot Fly Gyrostigma rhinocerontis (Diptera: Oestridae).

Simple SummaryGyrostigma rhinocerontis (Hope), the rhinoceros bot fly, is a rare obligate intestinal parasite of white and black rhinoceroses that can cause severe myiasis and secondary infection, leading to enormous economic and scientific loss. As the main sensory organs of flies, the antennae provide insects with critical information about the environment, playing significant roles in their key activities. The antennal characteristics of G. rhinocerontis remain largely unexplored, probably due to the extreme rarity of adult specimens in collections. In this study, the antennae of G. rhinocerontis were thoroughly examined using light and scanning electron microscopy. The morphology, including detailed ultrastructure, of antennal sensilla are presented. As the largest species of Oestridae Leach, not surprisingly, G. rhinocerontis has significantly larger antennae with more sensilla and sensory pits than any other Oestridae species, which could be an adaptation to locate their rare and endangered hosts.Gyrostigma rhinocerontis (Diptera: Oestridae) is a rare obligate intestinal parasite of both white and black rhinoceroses, which can induce severe myiasis, cause secondary infection, and lead to enormous economic and scientific loss. Antennae are the main sensory organs of G. rhinocerontis, which may have evolved a series of specialized adaptive structures to facilitate the exploitation of their hosts. Here, we thoroughly examine the antennae of G. rhinocerontis via light and scanning electron microscopy. Only microtrichia and chaetic sensilla were observed on the scape and pedicel, and the latter is enlarged, half-enveloping the postpedicel. Four types of sensilla (trichoid sensilla, basiconic sensilla, coeloconic sensilla, and clavate sensilla) and sensory pits are detected on the postpedicel. A set of coeloconic sensilla and a chaetic sensillum are located on the arista. Distribution, type, size, and ultrastructure of antennal sensilla are presented. The antennae of G. rhinocerontis are the largest among Oestridae species, with the most sensilla and the most sensory pits. These antennal characteristics could be correlated to their adaptation for more sensitive and accurate olfactory organs, used to locate their rare and endangered hosts. Accordingly, this morphological evidence supports that the host is an important driving factor in the diversity of antennal morphology in the bot flies.

Transitional morphology and Afrotropical affinity of a bythinoplectine rove beetle from the early Eocene of India (Coleoptera: Staphylinidae: Pselaphinae)

Recently discovered Ypresian-age amber from Cambay, India, reveals an ancient arthropod assemblage on the Indian subcontinent during its collision with Asia. Despite the tectonic history of India, limited connections have been found between the Cambay palaeofauna and present-day Madagascan and mainland African faunas. Here, I describe a new fossil pselaphine rove beetle (Staphylinidae: Pselaphinae) recovered from the Cambay deposit that shows closest apparent phylogenetic affinity to modern Afrotropical genera. Yprezethinus grimaldii gen. et sp. nov. is placed in Bythinoplectini, subtribe Bythinoplectina. Based on antennal and maxillary palp morphology, Yprezethinus is a putative transitional stem lineage of the Zethinus-group of genera—an extant clade distributed across equatorial African rainforests. Although Yprezethinus shares with this clade the derived feature of ovoid antennal clubs formed by tight appression of the apical two segments, it differs from its putative extant relatives in its possession of the plesiomorphic complement of 11 antennomeres, without any fusions of segments. The fossil taxon signifies a biotic link between early Eocene India and continental Africa, and marks the Cenozoic emergence of a tropical leaf litter arthropod fauna approaching that of contemporary, ant-dominated rainforests.

Revisiting trends in morphology of antennal sensilla in scarabaeoid beetles

Phytophagous scarab beetles associated with angiosperms have characteristically enlarged lamellate antennae and exhibit a striking morphological variation of sensilla. In this study, we compared the morphology of antennal surface of 62 species Scarabaeoidea using SEM microscopy, particularly also in light of their evolution in association with angiosperms. We investigated the correlation of antennal sensilla morphology, i.e., their structure and distribution, with species diversity and lineage diversification rates. A high diversity of sensilla was observed but also multiple transitional forms, even on the same antennomere. We interpreted this as evidence for a high evolutionary plasticity. We recognized clear patterns of convergence and repeated evolution of certain types of placoid sensilla. One main tendency found in the phytophagous Pleurostict chafers was a shift from sensilla trichodea to placoid-like sensilla, apparently also enhanced by the increase of the lamellate antennal surface, either by size or number of the lamellae. This trend occurred not only in the Pleurosticts, but also in Glaphyridae, a second angiosperm-associated lineage of Scarabaeoidea. However, our results suggest no direct relation between species diversity or the rate of diversification and general sensilla morphology, i.e., the origin of placoid sensilla. This could be explained not only by species-poor lineages also possessing placoid sensilla but also by otherwise successful and species rich groups having sensilla trichodea (e.g., dung beetles). Results further reveal the need to refine current phylogenetic hypotheses by more comprehensive taxon sampling and to expand the molecular characterization of pheromones and odor binding proteins to better understand the role of chemical communication in scarab diversification.

Ultrastructure Characteristics and Sexual Dimorphism of Antennal Sensilla in Tirathaba rufivena (Lepidoptera: Pyralidae).

Simple SummaryTo elucidate the external morphology and internal structures of antennal sensilla that could play a role in locating host plants and mates, we describe and further characterize the ultrastructure, abundance and distribution of nine sensilla types in both sexes using scanning electron microscopy and transmission electron microscopy. Sexual dimorphism mainly occurs in variation in the length of sensilla basiconica, sensilla chaetica, sensilla coeloconica 1 and Böhm sensilla, and the abundance of sensilla basiconica, sensilla auricillica 1 and sensilla auricillica 2. The possible structural function of each kind of sensillum is discussed. These results provide direct morphological evidence that the antennae of Tirathaba rufivena possess structures that can play a role in locating mates and host plants.Tirathaba rufivena Walker, a major insect pest of Areca catechu L., has severely threatened areca nut cultivation in Hainan, China. To improve our understanding of the communication mechanism in host plant seeking and mate-finding for T. rufivena, we described and further characterized the external morphology and internal sensilla structures using scanning electron microscopy and transmission electron microscopy in this study. The antennal morphology was similar between males and females, and there was no significant difference in length between the two sexes. In total, nine sensilla types were identified: sensilla trichodea (Str), sensilla chaetica (Sch), sensilla basiconica (Sba), sensilla auricillica (Sau), sensilla coeloconica (Sco), sensilla styloconica (Sst), Böhm sensilla (Bs), uniporous peg sensilla (Ups) and sensilla squamiformia (Ssq). Sexual dimorphism mainly occurs in variation in the length of Sba, Sch, Sco1 and Bs, and the abundance of Sba, Sau1 and Sau2. The Sba had larger size and numbers on female antennae than that on males, suggesting that these sensilla might have important roles in locating host plants. Both Sau1 and Sau2 were significantly more abundant in females and were probably associated with the detection of mates and host plant for oviposition. These data were important for ongoing studies on host plant seeking and mate-finding behavior in T. rufivena and provided a theoretical foundation to further studies of semiochemical control for this pest.

Movement and olfactory signals: Sexually dimorphic antennae and female flightlessness in moths

Darwin argued a role for sexual selection in the evolution of male sensory structures, including insect antennae, the strength of which will depend upon the importance of early arrival at receptive females. There is remarkable variation in the nature and degree of sexual dimorphism in moth antennae, with males of some species having spectacular, feathery antennae. Although it is widely assumed that these elaborate structures provide greater sensitivity to chemical signals (sex pheromones), the factors underlying the interspecific diversity in male antennal structure and size are poorly understood. Because male antennal morphology may be affected by several female life–history traits, including flight ability, we conducted a phylogenetic comparative analysis to test how these traits are linked, using data from 93 species of moths across 11 superfamilies. Our results reveal that elaborate antennae in males have evolved more frequently in species where females are monandrous. Further, female loss of flight ability evolved more frequently in species where males have elaborate antennae. These results suggest that elaborate antennae have evolved in response to more intense male competition, arising from female monandry, and that the evolution of elaborate antennae in males has, in turn, shaped the evolution of female flightlessness.

Ultrastructure of Antennal Sensory Organs in Nine Flesh Flies (Diptera: Sarcophagidae): New Insight into the Definition of Family Sarcophagidae

Simple SummaryThe antennal sensilla of species in all three subfamilies of Sarcophagidae are studied for the first time via scanning electron microscopy. The morphology, density, and distribution of each type are described for each species. A total of eight types of antennal sensilla (chaetic sensilla, setiferous plaques, pedicellar buttons, trichoid sensilla, basiconic sensilla, coeloconic sensilla, clavate sensilla, bottle-shaped sensilla) and sensory pits are found in both sexes. The existence of bottle-shaped sensilla in the sensory pits in all three subfamilies of the sarcophagid species suggests a potential synapomorphy of sarcophagids and a new morphological diagnosis character of the family Sarcophagidae.The antennae are the main olfactory organ of flies, playing key roles in their survival and the success of all life stages. Antennal ultrastructural morphology has been well described in the representative species of most calyptrate families, yet only a few studies have focused on Sarcophagidae species, those with ecological and medical relevance. Antennal morphology and the types, shapes, distribution, and density of the antennal sensilla of nine Sarcophagidae species are studied in detail with scanning electron microscopy, including Miltogramminae: Metopia campestris (Fallén) and Mesomelena mesomelaena (Loew), Paramacronychiinae: Agria mihalyii (Rohdendorf & Verves), Wohlfahrtia bella (Macquart), and W. magnifica (Schiner); Sarcophaginae: Sarcophaga (Parasarcophaga) albiceps Meigen, S. (Bercaea) africa (Wiedemann), S. (Boettcherisca) peregrina (Robineau-Desvoidy), and S. (Liosarcophaga) portschinskyi (Rohdendorf), covering all three subfamilies of this family. The morphology of the three segments of the antennae has been described. The scape has only one type of chaetic sensilla, while three subtypes of chaetic sensilla were detected on the pedicel. The postpedicel has four types of sensilla: trichoid sensilla, coeloconic sensilla, clavate sensilla, and three subtypes of basiconic sensilla. Bottle-shaped sensilla were observed in sensory pits on the postpedicel in all nine species. These sensilla have not been discovered in other calyptrate species, suggesting that they are a potential sarcophagid synapomorphy.

Experimental immune challenges reduce the quality of male antennae and female pheromone output

Sexual signalling is a key feature of reproductive investment, yet the effects of immune system activation on investment into chemical signalling, and especially signal receiver traits such as antennae, are poorly understood. We explore how upregulation of juvenile immunity affects male antennal functional morphology and female pheromone attractiveness in the gumleaf skeletonizer moth, Uraba lugens. We injected final-instar larvae with a high or low dose of an immune elicitor or a control solution and measured male antennal morphological traits, gonad investment and female pheromone attractiveness. Immune activation affected male and female signalling investment: immune challenged males had a lower density of antennal sensilla, and the pheromone of immune-challenged females was less attractive to males than their unchallenged counterparts. Immune challenge affected female investment into ovary development but not in a linear, dose-dependent manner. While there was no effect of immune challenge on testes size, there was a trade-off between male pre- and post-copulatory investment: male antennal length was negatively correlated with testes size. Our study highlights the costs of elaborate antennae and pheromone production and demonstrates the capacity for honest signalling in species where the costs of pheromone production were presumed to be trivial.

Antennal Morphology and Fine Structure of Flagellar Sensilla in Hippoboscid Flies with Special Reference to Lipoptena fortisetosa (Diptera: Hippoboscidae).

Simple SummaryIn insects, host searching usually involves different kinds of stimuli, both visual and chemical, that may act in combination. External cues are perceived through specific sensory organs (sensilla), mainly present on the antennae. Understanding how ectoparasites belonging to the Hippoboscidae locate their hosts is crucial, since these flies infest animals and can attack humans, with veterinary and medical implications. The aim of this research was to study the antennae of four hippoboscid species, Lipoptena cervi (Linnaeus, 1758), Lipoptena fortisetosa Maa, 1965, Hippobosca equina Linnaeus, 1758, and Pseudolynchia canariensis (Macquart, 1840), investigating the morphology and the sensory structures present on these appendages. A typical conformation of the antennae with the envelopment of the third segment (flagellum) inside the first two have been observed. Moreover, two types of sensilla have been detected and their role in the perception of host odours and CO2 have been hypothesized. Other antennal structures seem to be involved in the detection of temperature and humidity variations. Our findings confirm that these hippoboscids use chemoreception for host location, giving insights into this complex process in this poorly investigated group.Lipoptena cervi (Linnaeus), Lipoptena fortisetosa Maa, Hippobosca equina Linnaeus, and Pseudolynchia canariensis (Macquart) are hematophagous ectoparasites that infest different animal species and occasionally bite humans. Hosts are located by a complex process involving different kinds of stimuli perceived mainly by specific sensory structures on the antennae, which are the essential olfactory organs. General antennal morphology, together with distribution and ultrastructure of sensilla, have been studied in detail with scanning and transmission electron microscopy approaches. Observations have revealed some common features among the four studied hippoboscids: (a) typical concealment of the flagellum inside the other two segments; (b) characteristic trabecular surface of the flagellum; (c) peculiar external microtrichia; (d) presence on the flagellum of basiconic sensilla and grooved peg coeloconic sensilla; (e) unarticulated arista. The ultrastructure of L. fortisetosa revealed that microtrichia and the flagellar reticulated cuticle are not innervated. Different roles have been hypothesized for the described antennal structures. Microtrichia and the reticulated cuticle could convey volatile compounds towards the flagellar sensory area. Peculiar sensory neurons characterize the unarticulated arista which could be able to detect temperature variations. Coeloconic sensilla could be involved in thermoreception, hygroreception, and carbon dioxide reception at long distances, while the poorly porous basiconic sensilla could play a role in the host odour perception at medium–short distances.