BACKGROUND: Lucilia cuprina (Wiedemann, 1830) (Diptera: Calliphoridae) is the main causative agent of flystrike of sheep in Australia and New Zealand. Female flies lay eggs in an open wound or natural orifice, and the developing larvae eat the host\'s tissues, a condition called myiasis. To improve our understanding of host-seeking behavior, we quantified gene expression in male and female antennae based on their behavior.
METHODS: A spatial olfactometer was used to evaluate the olfactory response of L. cuprina mated males and gravid females to fresh or rotting beef. Antennal RNA-Seq analysis was used to identify sensory receptors differentially expressed between groups.
RESULTS: Lucilia cuprina females were more attracted to rotten compared to fresh beef (> fivefold increase). However, males and some females did not respond to either type of beef. RNA-Seq analysis was performed on antennae dissected from attracted females, non-attracted females and males. Transcripts encoding sensory receptors from 11 gene families were identified above a threshold (≥ 5 transcript per million) including 49 ATP-binding cassette transporters (ABCs), two ammonium transporters (AMTs), 37 odorant receptors (ORs), 16 ionotropic receptors (IRs), 5 gustatory receptors (GRs), 22 odorant-binding proteins (OBPs), 9 CD36-sensory neuron membrane proteins (CD36/SNMPs), 4 chemosensory proteins (CSPs), 4 myeloid lipid-recognition (ML) and Niemann-Pick C2 disease proteins (ML/NPC2), 2 pickpocket receptors (PPKs) and 3 transient receptor potential channels (TRPs). Differential expression analyses identified sex-biased sensory receptors.
CONCLUSIONS: We identified sensory receptors that were differentially expressed between the antennae of both sexes and hence may be associated with host detection by female flies. The most promising for future investigations were as follows: an odorant receptor (LcupOR46) which is female-biased in L. cuprina and Cochliomyia hominivorax Coquerel, 1858; an ABC transporter (ABC G23.1) that was the sole sensory receptor upregulated in the antennae of females attracted to rotting beef compared to non-attracted females; a female-biased ammonia transporter (AMT_Rh50), which was previously associated with ammonium detection in Drosophila melanogaster Meigen, 1830. This is the first report suggesting a possible role for ABC transporters in L. cuprina olfaction and potentially in other insects.

Alternative splicing is an essential post-transcriptional regulatory mechanism that diversifies gene function by generating multiple protein isoforms from a single gene and act as a crucial role in insect environmental adaptation. Olfaction, a key sense for insect adaptation, relies heavily on the antennae, which are the primary olfactory organs expressing most of the olfactory genes. Despite the extensive annotation of olfactory genes within insect antennal tissues facilitated by high-throughput sequencing technology advancements, systematic analyses of alternative splicing are still relatively less. In this study, we focused on the oriental fruit fly (Bactrocera dorsalis), a significant pest of fruit crops. We performed a detailed analysis of alternative splicing in its antennae by utilizing the full-length transcriptome of its antennal tissue and the insect\'s genome. The results revealed 8600 non-redundant full-length transcripts identified in the oriental fruit fly antennal full-length transcriptome, spanning 4,145 gene loci. Over 40% of these loci exhibited multiple isoforms. Among these, 161 genes showed sex-biased isoform switching, involving seven different types of alternative splicing. Notably, events involving alternative transcription start sites (ATSS) and alternative transcription termination sites (ATTS) were the most common. Of all the genes undergoing ATSS and ATTS alternative splicing between male and female, 32 genes were alternatively spliced in protein coding regions, potentially affecting protein function. These genes were categorized based on the length of the sex-biased isoforms, with the highest difference in isoform fraction (dIF) associated with the ATSS type, including genes such as BdorABCA13, BdorCAT2, and BdorTSN3. Additionally, transcription factor binding sites for doublesex were identified upstream of both BdorABCA13 and BdorCAT2. Besides being expressed in the antennal tissues, BdorABCA13 and BdorCAT2 are also expressed in the mouthparts, legs, and genitalia of both female and male adults, suggesting their functional diversity. This study reveals alternative splicing events in the antennae of Bactrophora dorsalis from two aspects: odorant receptor genes and other types of genes expressed in the antennae. This study not only provides a research foundation for understanding the regulation of gene function by alternative splicing in the oriental fruit fly but also offers new insights for utilizing olfaction-based behavioral manipulation techniques to manage this pest.

Insects must fly in highly variable natural environments filled with gusts, vortices, and other transient aerodynamic phenomena that challenge flight stability. Furthermore, the aerodynamic forces that support insect flight are produced from rapidly oscillating wings of time-varying orientation and configuration. The instantaneous flight forces produced by these wings are large relative to the average forces supporting body weight. The magnitude of these forces and their time-varying direction add another challenge to flight stability, because even proportionally small asymmetries in timing or magnitude between the left and right wings may be sufficient to produce large changes in body orientation. However, these same large magnitude oscillating forces also offer an opportunity for unexpected flight stability through non-linear interactions between body orientation, body oscillation in response to time varying inertial and aerodynamic forces, and the oscillating wings themselves. Understanding the emergent stability properties of flying insects is a crucial step toward understanding the requirements for evolution of flapping flight and decoding the role of sensory feedback in flight control. Here we provide a brief review of insect flight stability, with some emphasis stability effects brought about by oscillating wings, and present some preliminary experimental data probing some aspects of flight stability in free-flying insects.

The lycid genus Ponyalis Fairmaire, 1899 is reviewed. Six new species are described from China, including P.longicornis sp. nov., P.truncata sp. nov., P.dabieshanensis sp. nov., P.hainanensis sp. nov., P.quadricollimima sp. nov., and P.zhejiangensis sp. nov. Nine previously known species, including P.alternata (Pic, 1927), P.fukiensis (Bocak, 1999), P.gracilis (Bocak, 1999), P.himalejica (Bourgeois, 1885), P.klapperichi (Bocak, 1999), P.laticornis Fairmaire, 1899, P.nigrohumeralis (Pic, 1939), P.quadricollis (Kiesenwetter, 1874), and P.variabilis Li, Bocak & Pang, 2015 are illustrated with images of the habitus and aedeagi to make the comparisons with the new species. In addition, a distribution map and an identification key to all 24 species of Ponyalis are provided.

Endoclita signifer is a prominent wood-boring insect species in eucalyptus plantations in Guangxi, China, causing significant ecological and economic damage. A novel approach to controlling the challenging wood-boring pest involves disrupting the olfactory communication between insects and the volatile compounds emitted by plants. To identify the olfactory proteins contributing to host selection based on 11 GC-EAD-active volatiles from eucalyptus leaves and to discover the highly expressed olfactory proteins, we conducted a study on the antennal transcriptomes of adult E. signifer and screened key olfactory proteins in the antennae. We identified a total of 69 olfactory proteins. When compared to the larval transcriptomes, the antennal transcriptome of adult E. signifer revealed the presence of 17 new odorant-binding proteins (OBPs), including 2 pheromone-binding proteins (PBPs), 7 previously unreported chemosensory proteins (CSPs), 17 new odorant receptors (ORs), 4 new gustatory receptors (GRs), 11 novel ionotropic receptors (IRs), and 2 sensory neuron membrane proteins (SNMPs). Through the phylogenetic tree of OBPs and ORs, we identified EsigPBP2 and EsigPBP3 as two of the three PBPs, designated EsigOR13 as EsigOrco, and recognized EsigOR10 and EsigOR22 as the newly discovered EsigPRs in E. signifer. In the adult antennae, the expression levels of EsigGOBP14, EsigGOBP13, EsigOBP14, EsigOBP17, EsigCSP14, and EsigOR16 were notably high, indicating that these proteins could be pivotal in binding to plant volatiles.

BACKGROUND: Odorant-binding proteins (OBPs) are essential in insect\'s daily behaviors mediated by olfactory perception. Megachile saussurei Radoszkowski (Hymenoptera, Megachilidae) is a principal insect pollinating alfalfa (Medicago sativa) in Northwestern China. The olfactory function have been less conducted, which provides a lot of possibilities for our research.
RESULTS: Our results showed that 20 OBPs were identified in total. Multiple sequence alignment analysis indicated MsauOBPs were highly conserved with a 6-cysteine motif pattern and all belonged to the classic subfamily, coding 113-196 amino acids and sharing 41.32%-99.12% amino acid identity with known OBPs of other bees. Phylogenetic analysis indicated there were certain homologies existed among MsauOBPs and most sequences were clustered with that of Osmia cornuta (Hymenoptera, Megachilidae). Expression analysis showed the identified OBPs were mostly enriched in antennae instead of other four body parts, especially the MsauOBP2, MsauOBP3, MsauOBP4, MsauOBP8, MsauOBP11 and MsauOBP17, in which the MsauOBP2, MsauOBP4 and MsauOBP8 presented obvious tissue-biased expression pattern. Molecular docking results indicated MsauOBP4 might be the most significant protein in recognizing alfalfa flower volatile 3-Octanone, while MsauOBP13 might be the most crucial protein identifying (Z)-3-hexenyl acetate. It was also found the lysine was a momentous hydrophilic amino acid in docking simulations.
CONCLUSIONS: In this study, we identified and analyzed 20 OBPs of M. saussurei. The certain homology existed among these OBPs, while some degree of divergence could also be noticed, indicating the complex functions that different MsauOBPs performed. Besides, the M. saussurei and Osmia cornuta were very likely to share similar physiological functions as most of their OBPs were clustered together. MsauOBP4 might be the key protein in recognizing 3-Octanone, while MsauOBP13 might be the key protein in binding (Z)-3-hexenyl acetate. These two proteins might contribute to the alfalfa-locating during the pollination process. The relevant results may help determine the highly specific and effective attractants for M. saussurei in alfalfa pollination and reveal the molecular mechanism of odor-evoked pollinating behavior between these two species.

Glutathione transferases (GST) are detoxification enzymes that conjugate glutathione to a wide array of molecules. In the honey bee Apis mellifera, AmGSTD1 is the sole member of the delta class of GSTs, with expression in antennae. Here, we structurally and biochemically characterized AmGSTD1 to elucidate its function. We showed that AmGSTD1 can efficiently catalyse the glutathione conjugation of classical GST substrates. Additionally, AmGSTD1 exhibits binding properties with a range of odorant compounds. AmGSTD1 has a peculiar interface with a structural motif we propose to call \'sulfur sandwich\'. This motif consists of a cysteine disulfide bridge sandwiched between the sulfur atoms of two methionine residues and is stabilized by CH…S hydrogen bonds and S…S sigma-hole interactions. Thermal stability studies confirmed that this motif is important for AmGSTD1 stability and, thus, could facilitate its functions in olfaction.

Species in Ectrichodiinae are known for their prey specialization on millipedes. However, knowledge of the morphological adaptations to this unique feeding habit was limited. In the current study, we examined the microstructures of the antennae, mouthparts, and legs of four millipede feeding ectrichodiines, Ectrychotes andreae (Thunberg, 1888), Haematoloecha limbata Miller, 1953, Labidocoris pectoralis (Stål, 1863), and Neozirta eidmanni (Taueber, 1930), and compared them with those of three species of tribelocephalines, a group closely related to Ectrichodiinae. On the antennae, we found four types of antennal sensilla. On the mouthparts, we recognized four types of labial sensilla. Sampled ectrichodiines have distinctly more and denser slightly transverse ridges on the external side of mandibles than tribelocephalines. E. andreae and H. limbata possess numerous small papillae fringed with densely arranged finger-print-like grains on the trochanter and femur; these probably facilitate the immobilization of prey. Overall, our study illustrates, at a microstructural level, the remarkable morphological adaption of prey manipulation in ectrichodiine, and has enhanced our understanding about stenophagy in the family Reduviidae.

The olfactory system plays a fundamental role in mediating insect behaviour. Worker bees exhibit an age-dependent division of labour, performing discrete sets of behaviours throughout their lifespan. The behavioural states of bees rely on their sense of the environment and chemical communication via their olfactory system, the antennae. However, the olfactory adaptation mechanism of worker bees during their behavioural development remains unclear. In this study, we conducted a comprehensive and quantitative analysis of antennal gene expression in the Apis mellifera of newly emerged workers, nurses, foragers and defenders using RNA-seq. We found that the antenna tissues of honey bees continued developing after transformation from newly emerged workers to adults. Additionally, we identified differentially expressed genes associated with bee development and division of labour. We validated that major royal jelly protein genes are highly and specifically expressed in nurse honey bee workers. Furthermore, we identified and validated significant alternative splicing events correlated with the development and division of labour. These findings provide a comprehensive transcriptome profile and a new perspective on the molecular mechanisms that may underlie the worker honey bee division of labour.

The bamboo bug Notobitus meleagris (Fabricius, 1787) is a serious pest of bamboo shoots in China, India, Myanmar, Vietnam, and Singapore. The antennae of the nymphal instars and adults of N.meleagris are involved in communication among individuals and finding the host plants. In order to understand the morphology of antennal sensilla, their types, and the distribution of sensilla on the antennae of nymphal instars and adults in N. meleagris, we studied the morphology of antennal sensilla with a scanning electron microscope. The antennae of the nymphs and adults comprised the scape, pedicel, and two flagellomeres. Four types and eight subtypes of sensilla were identified in the nymphal instars (sensilla trichodea [St].1, St.2, St.3, sensilla basiconica [Sb].1, Sb.2, sensilla chaetica [Sc].1, Sc.2, sensilla coeloconica [Sco].1), whereas those of the adults had five types and eleven subtypes of sensilla (St.1, St.2, St.3, Sb.1, Sb.2, Sb.3, Sc.1, Sc.2, Sco.1, Sco.2, and sensilla campaniformia [Sca]). There are significant differences in the number, type, and size of the sensilla in different nymphal instars, which increases with the increase in nymphal instars. There was no sexual dimorphism observed in the adult sensilla; however, the length and diameter of St.3, Sb.2, and Sb.3 were sexually dimorphic. The potential functions of each sensillum were discussed based on the morphology and distribution of the antennal sensilla and were compared with similar published studies. Our results provide primary data for further research on the behavioral mechanism, green prevention, and control of N. meleagris.