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A comparative SEM study of palp sensory surfaces in 25 caddisfly species representing seven families reveals seven types of sensilla: long trichoid, blunt chaetoid, campaniform, mushroom-like pseudoplacoid, petaloid, thick basiconic and thin basiconic sensilla. Long trichoid and chaetoid sensilla are present on all segments of both pairs of palps. First and second segments of maxillary palps bear groups of long and sclerotised chaetoid sensilla on their medial surface. Other segments of maxillary palps and all segments of labial palps have shorter and thinner chaetoid sensilla mainly on their ventromedial surfaces. Campaniform sensilla usually occur on the first segment of labial palps and second segment of maxillary palps. Mushroom-like pseudoplacoid sensilla may occupy all palp segments or only distal ones. Petaloid sensilla form sensory fields on apical segments of both pairs of palps in most studied species. Thick basiconic sensilla occur only in apical sensory complexes on tips of maxillary and labial palps. A comparison with the Lepidoptera suggests the similarity in palp sensilla and conservative evolution of the palp surface. The reconstructed ground plan for the palp sensory surfaces in Trichoptera and Amphiesmenoptera is provided.

A comparative morphological study of the structure and distribution of sensilla on the maxillary and labial palps in caddisflies of the family Hydropsychidae was performed. Morphology of palpal sensilla was studied by scanning electron microscopy in 17 species from 12 genera. The palps of the studied species have four types of sensilla: long trichoid, chaetoid, campaniform, and petaloid; at the same time, no basiconic and pseudoplacoid sensilla were found on the palps. All the studied species lack apical sensory complexes at the tips of both pairs of palps, where only long chaetoid sensilla are present. Petaloid sensilla form sensory fields on the 4th (in Arctopsychinae) or on the 3rd and 4th segments (in Diplectroninae, Hydropsychinae, Macronematinae) of the maxillary palps, but sensilla of this type are never present on the labial palps. The sensory fields include from 5–10 sensilla in Hydropsychinae to 40 sensilla in Arctopsychinae.

Monochamus saltuarius is an important wood-boring pest of forests and a vector insect for the transmission of Bursaphelenchus xylophilus in China and other East Asian regions. To gain insight into the Mo. saltuarius olfactory system, we characterized the sizes and morphological characteristics of sensilla on antennae, maxillary palps, and labial palps of adults by scanning electron microscopy. Eight types of antennal sensilla were identified on the antennae: Böhm bristles (BBs), sensilla chaetica (SChs, with subtypes SChI and SChII), sensilla trichodea (STs, with subtypes STI, STII and STIII), sensilla auricillica (SAus), sensilla basiconica (SBs, with subtypes SBI and SBII), sensilla grooved peg (SGPs), dome shaped organs (DSOs), and cuticular pores (CPs); among these, BBs, STIs, STIIs, SChIs, and SChIIs may be mechanoreceptors, and STIIIs, SAus, SBIs, SBIIs, SGPs and CPs may be chemoreceptors. Seven sensillum types were identified on maxillary palps and labial palps: BBs, STs (with subtypes STII, and STIII), SChs, sensilla placodea (SPs), sensilla coeloconica (SCos), CPs, and sensilla twig basiconica (STBs, with subtypes STBI, STBII, STBIII, and STBIV), among which BBs, STIIs, and SChs may be mechanoreceptors, and STIIIs, SPs, CPs, STBIs, STBIIs, STBIIIs, and STIVs may be chemoreceptors. DSOs on the antennae and SCos on the palps may be hydroreceptors, and/or thermoreceptors. The types and densities of sensilla increased from the base to the tip of the antennae, and sensilla with chemical-sensing functions were concentrated mostly on the flagellum. Identification of these sensillum types provides a basis for analyzing the mechanisms of host recognition and environmental perception of Mo. saltuarius .

Because of its importance as a malaria vector, Anopheles coluzzii's Coetzee & Wilkerson olfactory system has been studied extensively. Among this work is a series of studies comparing the expression of chemosensory genes in olfactory organs in females and/or males of these species. These have identified species- and female-biased chemosensory gene expression patterns. However, many questions remain about the role of chemosensation in male anopheline biology. To pave the way for future work we used RNAseq to compare chemosensory gene expression in the male maxillary palps of An. coluzzii and its sibling species An. quadriannulatus Theobald. As expected, the chemosensory gene repertoire is small in the male maxillary palps. Both species express the tuning receptors Or8 and Or28 at relatively high levels. The CO2 receptor genes Gr22-Gr24 are present in both species as well, although at much lower level than in females. Additionally, several chemoreceptors are species-specific. Gr37 and Gr52 are exclusive to An. coluzzii, whereas Or9 and Gr60 were detected only in An. quadriannulatus. Furthermore, several chemosensory genes show differential expression between the two species. Finally, several Irs, Grs, and Obps that show strong differential expression in the female palps, are absent or lowly expressed in the male palps. While many questions remain about the role of chemosensation in anopheline male biology, these results suggest that the male maxillary palps could have both a sex- and species-specific role in the perception of chemical stimuli. This work may guide future studies on the role of the male maxillary palp in these species.

Megabruchidius dorsalis (Fåhraeus, 1839) (Coleoptera: Bruchinae) is an important pest that damages the seeds of Gleditsia L. (Fabaceae: Caesalpinioideae). This beetle searches for host plants with its sensory system. To further explore the mechanisms of host location and to understand the ultrastructure of M. dorsalis, we examined the morphology and distribution of its sensilla on the antennae and mouthparts of male and female adults, using scanning electron microscopy (SEM). Both male and female antennae are serrated and can be divided into scape, pedicel, and flagellum. There were seven types and eight subtypes of antennal sensilla, including Bőhm bristles (BB), two subtypes of sensilla trichoid (ST1, ST2), two subtypes of sensilla chaetica (SC1, SC2), four subtypes of sensilla basiconic (SB1, SB2, SB3, SB4), sensilla cavity (SCa), sensilla auricillica (SA), and sensilla gemmiformium (SG). Five types of maxillary and labial palp sensilla in the mouthparts were observed: sensilla chaetica (SC), sensilla trichoidea (ST), sensilla styloconica (SSt), sensilla coeloconica (SCo), and sensilla digitiform (SD). No sexual dimorphism in sensilla type was observed, but there were variations between males and females in the numbers and distribution along the antennae. There were more SA in males than in females, while the number of ST sensilla in the maxillary palps were lower in males than in females. ST1 were most abundant in both sexes. We discussed potential function related to structure via comparisons with previous investigations of bruchids and other insects. Our results provide a theoretical basis for further studies on sensory physiological function, using semiochemicals as effective biological controls of M. dorsalis.

A relevant species in waste management but also in forensic, medical, and veterinary sciences is the black soldier fly, Hermetia illucens (Linnaeus; Diptera: Stratiomyidae). An ultrastructural study by scanning electron microscopy (SEM) was conducted for the first time on maxillary palps of both sexes, describing in detail the morphology and distribution of sensilla and microtrichia. The maxillary palps, composed of two segments, show sexual dimorphism in length and shape. In both sexes, the first segment is covered only by microtrichia, but the second one is divided into two parts: the proximal one, covered only by microtrichia, and the distal one containing both microtrichia and sensory structures. These structures include two types of sensory pits and one of chaetic sensilla. Due to sexual dimorphism in palp size, females have a higher number of sensory pits. The sexual dimorphism of palps and the presence and role of sensilla in H. illucens was discussed in comparison to other species of the family Stratiomyidae and of other Diptera. This study may represent a base for further investigations on mouthpart structures of this species, involved in key physiological activities, such as feeding, mating and oviposition.

The sterile insect technique (SIT) and male annihilation technique (MAT) are important tools for the control of Queensland fruit fly (Q-fly), Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), a major insect pest of horticultural crops in Australia. In MAT, mature Q-fly males are attracted to a toxic bait using Cuelure, a synthetic analog of raspberry ketone (RK). Substantial improvements in control could be achieved by simultaneous use of SIT and MAT, but this requires suppression of the Cuelure response in released sterile flies. Recent studies report that prerelease feeding with RK during the first 48 h after emergence can reduce the response of mature Q-fly males to Cuelure, but the mechanism underpinning this is unknown. Here, to test whether reduced sensory sensitivity to Cuelure is involved, we evaluated the effects of RK supplements, adult diet (yeast-supplemented diet throughout adult stage vs yeast-supplemented diet only for 48 h), and age on electroantennogram (EAG) and electropalpogram (EPG) responses of Q-flies to Cuelure stimuli. EAG responses did not vary with RK supplements, sex, or age of Q-flies fed yeast-supplemented diet throughout the adult stage, but the responses of Q-flies fed other diet regime decreased with age. EPG responses of both sexes of Q-flies were affected by RK supplements, age, and their interaction, but without patterns that might indicate reduced maxillary palp response of RK supplemented flies to Cuelure. Our findings do not support the hypothesis that reduced Cuelure response of male Q-flies fed RK supplements is explained by reduced electrophysiological response in antennae or maxillary palps.

The ultrastructure of the mouthparts of Haematobia irritans (L.) was investigated by scanning electron microscopy. The morphological characteristics of the maxillary palps, labium (prementum and postmentum), labrum, hypopharynx, haustellum, and labellar lobes are described, as well as of the sensilla evidenced on all the surface of the mouthparts, and the set of different positions assumed by the mouth apparatus of this fly. Based on their morphology, 12 well-differentiated sensilla were identified, among three types of cuticular sensilla: trichoidea, coeloconica, and campaniformia. A slight sexual dimorphism in the sensilla patterns found in the mouthparts of H. irritans was evidenced. These observations are discussed with reference to the current literature on the functional morphology of sense organs of Insecta. These results could facilitate the recognition of the chemosensory sensilla by electrophysiological techniques, and foment future taxonomic and phylogenetic studies to better elucidate the evolution of Diptera, Muscomorpha.

The scent of man Many insects are equipped with neurons that detect carbon dioxide. The use to which they are put varies according to the insect's ecology: hawk-moths use it as a measure of the quality of datura flowers. Closer to home, mosquitoes and other blood-feeders are attracted to the carbon dioxide emitted by us. Drosophila too has these sensors: two receptors, called Gr21a and Gr63a, have now been identified in the fruit fly. Flies with only one of the two are insensitive to carbon dioxide, but when both genes are expressed the neurons are sensitive to the gas. Similar genes are present in the malaria mosquito, so they may be useful targets for drugs aimed at reducing the ability of mosquitoes to find humans to bite. Identification of two CO 2 receptors in Drosophila antennae, Gr21a and Gr63a, determines that their co-expression is necessary and sufficient for CO 2 sensing. Flies lacking one of the two are insensitive to CO 2 , and confer CO 2 responsivity when both receptors are expressed in heterologous neurons. Blood-feeding insects, including the malaria mosquito Anopheles gambiae , use highly specialized and sensitive olfactory systems to locate their hosts. This is accomplished by detecting and following plumes of volatile host emissions, which include carbon dioxide (CO 2 ) 1 . CO 2 is sensed by a population of olfactory sensory neurons in the maxillary palps of mosquitoes 2 , 3 and in the antennae of the more genetically tractable fruitfly, Drosophila melanogaster 4 . The molecular identity of the chemosensory CO 2 receptor, however, remains unknown. Here we report that CO 2 -responsive neurons in Drosophila co-express a pair of chemosensory receptors, Gr21a and Gr63a , at both larval and adult life stages. We identify mosquito homologues of Gr21a and Gr63a , GPRGR22 and GPRGR24 , and show that these are co-expressed in A. gambiae maxillary palps. We show that Gr21a and Gr63a together are sufficient for olfactory CO 2 -chemosensation in Drosophila . Ectopic expression of Gr21a and Gr63a together confers CO 2 sensitivity on CO 2 -insensitive olfactory neurons, but neither gustatory receptor alone has this function. Mutant flies lacking Gr63a lose both electrophysiological and behavioural responses to CO 2 . Knowledge of the molecular identity of the insect olfactory CO 2 receptors may spur the development of novel mosquito control strategies designed to take advantage of this unique and critical olfactory pathway. This in turn could bolster the worldwide fight against malaria and other insect-borne diseases.

The classification of jumping spiders (Salticidae) is revised to bring it into accord with recent phylogenetic work. Of the 610 recognized extant and fossil genera, 588 are placed at least to subfamily, most to tribe, based on both molecular and morphological information. The new subfamilies Onomastinae, Asemoneinae, and Eupoinae, and the new tribes Lapsiini, Tisanibini, Neonini, Mopsini, and Nannenini, are described. A new unranked clade, the Simonida, is recognized. Most other family-group taxa formerly ranked as subfamilies are given new status as tribes or subtribes. The large long-recognized clade recently called the Salticoida is ranked as a subfamily, the Salticinae, with the name Salticoida reassigned to its major subgroup (the sister group to the Amycoida). Heliophaninae Petrunkevitch and Pelleninae Petrunkevitch are considered junior synonyms of Chrysillini Simon and Harmochirina Simon respectively. Spartaeinae Wanless and Euophryini Simon are preserved despite older synonyms. The genus Meata Żabka is synonymized with Gedea Simon, and Diagondas Simon with Carrhotus Thorell. The proposed relationships indicate that a strongly ant-like body has evolved at least 12 times in salticids, and a strongly beetle-like body at least 8 times. Photographs of living specimens of all 7 subfamilies, 30 tribes, and 13 subtribes are presented.