Female sex pheromone of Cystidia couaggaria couaggaria (Lepidoptera: Geometridae): identification and field attraction

The plum cankerworm moth, Cystidia couaggaria couaggaria (Geometridae: Ennominae), is a defoliator of Chinese plum trees (Prunus mume). The pheromone components of the female were analyzed by gas chromatography (GC) with an electro-antennographic (EAG) detector and GC coupled with mass spectrometry. The crude pheromone extract included several EAG-active components, i.e., trienyl, dienyl, and saturated hydrocarbons, with a C21-C25 straight chain. The characteristic mass spectra indicated the unsaturated hydrocarbons to be (3Z,6Z,9Z)-3,6,9-trienes and (6Z,9Z)-6,9-dienes. In the fields, mixtures of the synthetic C<21 and C<23 trienes in a ratio of 2:3 and 1:4 successfully attracted males of this diurnal species during daytime. While the male antennae responded to the C25 triene and saturated hydrocarbons, their synergistic effects were not observed on the male attraction in the fields. Addition of the C21 diene interestingly inhibited the activity of the triene mixture. Males of Cystidia truncangulata, a sympatric diurnal congener of C. c. couaggaria, showed similar EAG responses to the unsaturated hydrocarbons, but no C. truncangulata males were attracted by the lures tested for C. c. couaggaria males, indicating that the identified hydrocarbons comprised the species-specific pheromone of C. c. couaggaria females.     

Electrophysiological responses of Atta sexdens rubropilosa workers to essential oils of eucalyptus and its chemical composition

The leaf-cutting ant Atta sexdens rubropilosa Forel, 1908 is the most harmful of the Eucalyptus pests, causing severe losses in wood production through defoliation. Various strategies have been tried and effort spent on the development of methods to control this pest, however no practical and environmentally acceptable one currently exists. In this work the chemical composition of the essential oil of seven Eucalyptus species was identified and the selectivity and sensitivity of antennal receptors of A. sexdens rubropilosa workers to the volatile compounds were determined using the electroantennographic technique (EAG and GC-EAD). Analysis by GC-EAD showed in E. cloesiana and E. maculata, respectively, seventeen and sixteen terpenes that elicited responses in ant workers' antennae, indicating the potential role of the essential oils as allelochemicals that determine the choice of the foraging material.     

Electroantennographic bioassay as a screening tool for host plant volatiles

Plant volatiles play an important role in plant-insect interactions. Herbivorous insects use plant volatiles, known as kairomones, to locate their host plant. When a host plant is an important agronomic commodity feeding damage by insect pests can inflict serious economic losses to growers. Accordingly, kairomones can be used as attractants to lure or confuse these insects and, thus, offer an environmentally friendly alternative to pesticides for insect control. Unfortunately, plants can emit a vast number volatiles with varying compositions and ratios of emissions dependent upon the phenology of the commodity or the time of day. This makes identification of biologically active components or blends of volatile components an arduous process. To help identify the bioactive components of host plant volatile emissions we employ the laboratory-based screening bioassay electroantennography (EAG). EAG is an effective tool to evaluate and record electrophysiologically the olfactory responses of an insect via their antennal receptors. The EAG screening process can help reduce the number of volatiles tested to identify promising bioactive components. However, EAG bioassays only provide information about activation of receptors. It does not provide information about the type of insect behavior the compound elicits; which could be as an attractant, repellent or other type of behavioral response. Volatiles eliciting a significant response by EAG, relative to an appropriate positive control, are typically taken on to further testing of behavioral responses of the insect pest. The experimental design presented will detail the methodology employed to screen almond-based host plant volatiles by measurement of the electrophysiological antennal responses of an adult insect pest navel orangeworm (Amyelois transitella) to single components and simple blends of components via EAG bioassay. The method utilizes two excised antennae placed across a "fork" electrode holder. The protocol demonstrated here presents a rapid, high-throughput standardized method for screening volatiles. Each volatile is at a set, constant amount as to standardize the stimulus level and thus allow antennal responses to be indicative of the relative chemoreceptivity. The negative control helps eliminate the electrophysiological response to both residual solvent and mechanical force of the puff. The positive control (in this instance acetophenone) is a single compound that has elicited a consistent response from male and female navel orangeworm (NOW) moth. An additional semiochemical standard that provides consistent response and is used for bioassay studies with the male NOW moth is (Z,Z)-11,13-hexdecadienal, an aldehyde component from the female-produced sex pheromone.     

Perception of potential sex pheromones and host-associated volatiles in the cotton plant bug,Adelphocoris fasciaticollis (Hemiptera: Miridae): morphology and electrophysiology

Highly developed chemoreception allows insects to detect foods, find mates, and escape natural enemies. We described the structures and distributions of antennal chemosensilla in Adelphocoris fasciaticollis Reuter by scanning electron microscopy and transmission electron microscopy. Seven major types of antennal sensilla were identified in adults of both sexes. Types 1 and 2 are sensilla chaetica and have thick cuticular walls with conspicuous grooves at their surfaces. Types 3 and 4 are multiporous sensilla trichodea with 1–3 dendrites located at the sensillum lymph, indicating a putative olfactory function. Types 5 and 6 are typical sensilla basiconica but share different characteristics in both external morphology and internal ultrastructure, and may be involved in the perception of host-associated odorants. The last sensilla were Böhm bristles. In addition to the morphological characterization, electrophysiological responses of antennal chemosensilla to 51 semiochemicals were investigated based on electroantennogram (EAG) recordings. Results revealed that different chemical stimuli elicited significantly different dose-dependent EAG responses, in which potential sex pheromone components and green leaf volatiles showed relatively higher EAG responses, but neither monoterpenes nor sesquiterpenes can elicit favorable EAG values. The results provided direct morphological and electrophysiological evidence that the adult antennae of A. fasciaticollis could function in searching for mates and host plants.     

Ultrastructure and potential role of integumentary glandular cells in adult male and female Callosobruchus subinnotatus (Pic) and C. maculatus (Fabricius) (Coleoptera : Bruchidae)

Transmission and scanning electron microscopy methods were used to study the ultrastructure of integumentary glandular cells that may be involved in the production of sex pheromones and other semiochemicals in Callosobruchus subinnotatus and C. maculatus (Coleoptera : Bruchidae). Additionally, we measured electroantennogram (EAG) responses of male and female antennae to solvent extracts and glassadsorbed volatiles from both sexes of C. maculatus in order to localize the source of the putative sex pheromone. Both species have numerous cuticular pores on the abdomen and thorax. These pores open via an epicuticular duct into a single type 3 secretory cell. Solvent extracts of the pygidium from the female elicit the highest EAG responses from male antennae, suggesting this area of the abdomen to be the source of the putative sex pheromone in C. maculatus.     

Perception of cuticular hydrocarbons by the olfactory organs in Periplaneta americana (L.) (Insecta: Dictyoptera)

Despite the importance of cuticular hydrocarbons (CHs) in insect chemical communication, direct proof that they are detected and recognized by insects by contact or by olfactory receptors are rare. In Periplaneta americana, CHs induce aggregation. The aim of our study was to investigate how CHs are detected by P. americana antennae. Using solid phase microextraction and gas chromatography, the three main CHs of the species profile were identified in the volatiles emitted by these insects. Gas chromatography coupled to electroantennography recordings demonstrated that the antennae responded to these three CHs. Furthermore, CHs had an attraction effect in Y-olfactometer bioassays when presented at high concentrations. As CHs can be perceived by P. americana, at least from a short distance, they could play a role in attracting conspecifics during aggregation processes, in addition to inducing aggregation when direct contact is possible.     

Comparative study of the cuticular hydrocarbon composition of Melipona bicolor Lepeletier, 1836 (Hymenoptera, Meliponini) workers and queens

In social insects, cuticular hydrocarbons are involved in species, kin, caste and nestmate recognition. Gas chromatography and mass spectrometry were used to compare the cuticular hydrocarbon composition of workers, males and queens of Melipona bicolor. The cuticular hydrocarbon composition of this species was found to consist mainly of C23, C25:1, C25, C27:1, C27, C29:1 and C29, which are already present in imagoes that have not yet abandoned the brood cell. This composition varied quantitatively and qualitatively between and within the castes and sexes. The newly emerged workers and young queens (virgins) had similar cuticular hydrocarbon profiles, which were different from those of the males. When the females start executing their tasks in the colony, the cuticular hydrocarbon profile differences appear. The workers have less variety, while the queens conserve or increase the number of cuticular hydrocarbon compounds. The queens have more abdominal tegumentary glands than the workers, which apparently are the source of the new cuticular compounds.     

华北大黑鳃金龟对桃树挥发物的电生理反应

【目的】华北大黑鳃金龟Holotrichia oblita是一种分布范围广,寄主种类多的农业害虫。本研究鉴定了桃树顶空挥发物中对华北大黑鳃金龟雌虫具有触角电生理活性的化合物,并探索桃树挥发物活性成分的剂量对华北大黑鳃金龟雌、雄虫触角电生理反应的影响。【方法】采用顶空吸附法收集桃树枝叶挥发物,用气相色谱 触角电位联用技术(GC-EAD)和气相色谱 质谱联用技术(GC-MS)鉴定有电生理活性的桃树挥发物成分,最后用触角电位(electroantennograph, EAG)技术测试这些挥发物在0.01,0.1, 1, 10和100 μg剂量下引起的华北大黑鳃金龟雌、雄成虫EAG反应。【结果】桃树挥发物中能引起华北大黑鳃金龟雌成虫触角电生理反应的成分有7种,包括Z-β-罗勒烯、顺-3-己烯乙酸酯、顺-3-己烯醇、壬醛、水杨酸甲酯以及2种未知化合物。所测试的对华北大黑鳃金龟雌成虫触角具有电生理活性的5种桃树挥发物成分在各剂量下都能引起雌、雄成虫明显的EAG反应。雌、雄虫对同种物质的EAG反应随着剂量的增加而有增大的趋势,并且雌虫的EAG反应显著高于雄虫。【结论】桃树挥发物中,罗勒烯、顺-3-己烯乙酸酯、顺-3-己烯醇、壬醛、水杨酸甲酯均能引起华北大黑鳃金龟雌、雄成虫的剂量依赖性的触角电生理反应,而且存在显著的性别差异。可利用这些化合物开展行为反应和田间诱集试验,进一步验证其对华北大黑鳃金龟的引诱活性。     

Roles of Hydrocarbons in the Recognition Systems of Insects

SYNOPSIS. Many bioassays have shown that cuticular hydrocarbonsare used in the recognition systems of both solitary and socialinsects. The function of insect recognition systems is to enablean insect to recognize, and possibly discriminate, its own species,sex, or kin from that of other insects. The primary functionof cuticular hydrocarbons is to protect the insects from desiccation.Hydrocarbons can be removed from insect cuticles and characterizedwith gas chromatography/mass spectrometry. Studies using suchanalytical techniques have revealed that insect hydrocarboncompositions are species-specific, sex-specific and, in socialinsects, colony- and caste-specific. Furthermore, recognitionbioassays have confirmed that certain components of the cuticleof some insect species are sex attractants as well as aphrodisiacsor sex inhibitors. Other bioassays have shown that hydrocarbonsare important in facilitating colony structure in social insects.In addition, the hydrocarbons of some parasitic insects appearto mimic those of their host species. Thus, hydrocarbons areproving to be very important in the everyday activities of manyinsect species.     

昆虫触角转录组研究进展

昆虫通过信息交流感受内外坏境的变化,影响着昆虫定位、搜索食物源、寻找产卵地点和选择配偶等行为。在昆虫中,触角分布着较多的嗅觉感受器,可以感知挥发性分子、气味和激素,是昆虫重要的嗅觉器官,参与信息交流。综述和展望昆虫触角转录组的研究进展,有利于促进害虫管理、害虫防治和社会性昆虫级型分化与劳动分工的研究,也能为昆虫触角后续研究和昆虫触角仿生的应用提供参考。     

Divergence in cuticular hydrocarbons between parapatric subspecies of the meadow grasshopper, Chorthippus parallelus (Orthoptera, Acrididae)

Two subspecies of the grasshopper Chorthippus parallelus (Orthoptera; Acrididae) meet and form a hybrid zone in the Pyrenees. Here we investigate whether the subspecies differ in the blend of cuticular hydrocarbons. Such differences may function as chemical signals, being detected via contact chemoreception and used during mate choice as in other insects. Gas chromatography shows that the subspecies have diverged in the composition of their cuticular hydrocarbons. This difference between subspecies exists over and above variation in cuticular hydrocarbons among individual populations. The majority of the difference can be attributed to the relative amounts of a small group of compounds present in the cuticle. The possible consequences of this chemical divergence for mating encounters between the subspecies are discussed.     

暗黑鳃金龟对性信息素的触角电生理及行为反应

为了分离鉴定暗黑鳃金龟的性信息素成分并对其功能进行验证,本研究对比摸索了3种触角的处理方法,并进行同一浓度（30 ng·μL^-1）二元混合物、不同配比的触角EAG测试。结果包括: 建立了一种鳃叶状触角的触角电位（EAG）测定方法,即将暗黑鳃金龟Holotrichia parallela触角的各鳃叶用针分离开后进行测定,这种方法测得的触角电位反应值较高。雄虫触角对L-异亮氨酸甲酯和(R)-(-)-芳樟醇为7∶1的二元混合物的反应值最高,和暗黑鳃金龟雌虫性信息素25个腺体提取液的EAG反应相当;对同一配比（7∶1）不同剂量刺激液的EAG测试表明,雄虫对浓度为30 ng·μL^-1的二元混合物刺激液的反应值最高。嗅觉反应结果进一步证实,试虫对L-异亮氨酸甲酯和(R)-(-)-芳樟醇7∶1的选择最高,选择系数达93.3%。研究结果为利用性信息素防治暗黑鳃金龟技术的开发提供了基础。     

I smell where you walked – how chemical cues influence movement decisions in ants

Interactions between animals are not restricted to direct encounters. Frequently, individuals detect the proximity of others through cues unintentionally left by others, such as prey species assessing predation risk based on indirect predator cues. However, while the importance of indirect cues in predator–prey interactions has been intensely studied, their role in interactions among competitors, and their consequences for community structure, are little known to date. Ant communities are usually structured by aggressive interactions between competing species. Responding to cues of others should be useful to avoid competitors or discover food sources. In ants and other insects, such cues include chemical footprints, which they leave while walking. Here, we investigated how different ant species respond to footprints of others. Ant colonies were confronted with footprints of other colonies or species, and the workers chose between cue‐bearing and cue‐free areas. Moreover, we determined the chemical composition of footprints, and compared the absolute quantities of footprint and cuticular hydrocarbons. Ants of the species Lasius niger avoided footprints of non‐nestmate conspecifics, and tended to avoid footprints of two other species. We suggest that they avoided encounters with competitors to reduce costly fights. In contrast, three other ant species approached allospecific footprints, which may represent eavesdropping to find resources discovered by others. Three of the four ant species responded differently to nestmates and non‐nestmate footprints either through footprint‐following or antennation behavior. The chemical composition of footprints was species‐specific and largely congruent to cuticular hydrocarbons. Footprint quantities left by single workers represented 1/170 to 1/64 of the quantity of their cuticular hydrocarbons. We showed that chemical footprints represent an important cue for behavioral decisions in ants. The ability to identify and respond to chemical footprints may represent an important strategy for insects to cope with competing species or colonies in their habitat.     

Gas-chromatography and electroantennogram analysis of saturated hydrocarbons of cruciferous host plants and host larval body extracts of Plutella xylostella for behavioural manipulation of Cotesia plutellae

Saturated hydrocarbons (SHC) of five cruciferous host plants viz., cabbage, cauliflower, broccoli, knol khol and Brussels sprout and the larvae of diamondback moth (DBM), Plutella xylostella reared on these host plants were identified through gas-chromatography. The hydrocarbon profile of host plants and larval body extract of DBM reared on respective host plants revealed a wide variation in quantity as well as quality. Long chain hydrocarbons C26-C30 were detected in all the extracts. In electroantennogram (EAG) studies, SHCs at 10(-3) g dose elicited differential EAG response in the antennal receptors of gravid Cotesia plutellae females. Tricosane (C23) and hexacosane (C26) elicited 10-fold increased EAG response compared to control stimulus. Long chain hydrocarbons C27, C28 and C29 elicited, 6-7 fold increased responses. The sensitivity of antenna was 4-5 folds for C25, C14, C24, C15 and C30, while the short chain hydrocarbons elicited 2-3 fold increased EAG responses. Dual choice flight orientation experiments in a wind tunnel revealed that the gravid C. plutellae females preferred the odour of C16, C26, C29, C15, C21, C23, C30, C27, C24 and C22 as 60-70% females oriented and landed on SHC treated substrate compared to control odour, while the odour of eicosane (C20), pentacosane (C25) and octacosane (C28) were not preferred by the females.     

西花蓟马表皮碳氢化合物成份分析

西花蓟马Frankliniella occidentalis(Pergande)是一种重要的世界性害虫。为了明确西花蓟马表皮碳氢化合物的主要成分,本文采用改进的进样技术,利用气相色谱-质谱联用仪(GC-MS)对西花蓟马成虫和若虫表皮碳氢化合物进行分析。经NIST数据库检索,并与标准图谱比较,应用色谱峰面积归一法测定各种成分及其相对含量,实验结果表明,西花蓟马成虫和若虫表皮中的主要成分为C25～C29的直链和支链饱和烷烃;成虫表皮中含有9种碳氢化合物,若虫表皮中有8种碳氢化合物;9-甲基二十五烷是其成虫特有的,其它8种碳氢化合物是成虫与若虫共有的,但其含量略有差异。     

Effect of whitefly parasitoids on the cuticular lipid composition of Bemisia argentifolii (Homoptera: aleyrodidae) nymphs

Experiments were conducted to determine the effects of whitefly parasitoids on the cuticular lipid composition of the silverleaf whitefly, Bemisia argentifolii Bellows and Perring [=sweetpotato whitefly, Bemisia tabaci (Gennadius), Biotype B] nymphs. The cuticular lipids of B. argentifolii nymphs that had been attacked by parasitic wasps, either Eretmocerus mundus Mercet or Encarsia pergandiella Howard, were characterized by capillary gas chromatography and CGC-mass spectrometry and the results compared with the cuticular lipids of unparasitized nymphs. Previous studies with B. argentifolii nymphs had shown that wax esters were the major components of the cuticular lipids with lesser amounts of hydrocarbons, long-chain aldehydes, and long-chain alcohols. No appreciable changes in lipid composition were observed for the cuticular lipids of E. pergandiella-parasitized nymphs as compared to unparasitized controls. However, the cuticular lipids from nymphs parasitized by E. mundus contained measurable quantities of two additional components in their hydrocarbon fraction. Analyses and comparisons with an authentic standard indicated that the two hydrocarbons were the even-numbered chain length methyl-branched alkanes, 2-methyltriacontane and 2-methyldotriacontane. The occurrences and possible functions of 2-methylalkanes as cuticular lipid components of insects are discussed and specifically, in regard to host recognition, acceptance, and discrimination by parasitoids. Published 2000 Wiley-Liss, Inc.     

Oviposition deterrents from eggs of the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae): chemical identification and analysis by electroantennogram

Our previous results showed that an extract of the abdomens of mated females of the cotton bollworm, Helicoverpa armigera, deterred oviposition of conspecifics. In this paper, we found that the extract, in addition to reducing conspecifics’ oviposition, could elicit strong electroantennogram responses from mated females. The EAG elicitors mainly came from mature chorionated eggs in the ovarioles. Laid eggs or their surface extract evoked similar EAG responses. The main chemical components of the EAG elicitors from mature chorionated and laid eggs were myristic, palmitic, stearic, and oleic acids. A blend of authentic fatty acids at the ratio found in the laid eggs and in an amount equivalent to 100 laid eggs mimicked the EAG response and deterring effect. Moreover, these four oviposition-deterring fatty acids and their corresponding methyl esters evoked significantly higher EAG responses from both mated females and males than hexane blank and background. The EAG values differed among the test chemicals and between sexes. These results demonstrate that the four fatty acids from eggs are at least partially responsible for the oviposition-deterring effect of the extract from the abdomens of mated female H. armigera and that the moths may detect these chemicals olfactorily by antennae.     

Effects of a neonicotinoid insecticide (acetamiprid) on acetylcholinesterase activity and cuticular hydrocarbons profil in German cockroaches

Acetamiprid was incorporated into the diet at 2% dose corresponding to the LD50 and orally administrated to newly emerged adults of the German cockroach Blattella germanica and investigated on acetylcholinesterase activity and cuticular hydrocarbons profil. Acetylcholinesterase specific activity was determined on adult males and females after 24, 48 and 72 hours of treatment. Pentanic extracts of cuticular hydrocarbons in males and females after 6 days of treatment were analysed by gas chromatography. Data revealed an increase in acetylcholinesterase activity in both sexes from the control series. However, a significant inhibition in AChE was observed after treatment at 24, 48 and 72 hours especially in females. In addition, hydrocarbons profils were found qualitatively similar in all groups of insects. However, slight quantitative differences between sexes in control series were noted. Acetamiprid feminize the cuticular profil in males with significant reduction of cuticular compound, and these allowed separation of insects into two groups using multivariate analysis.     

Cuticular hydrocarbon pattern as a chemotaxonomy marker to assess six species of thrips

Thrips constitute several families of slender insects with fringed wings and unique asymmetrical mouthparts. They have become globally important pests, infesting a variety of agriculturally important crops. Species of thrips are difficult to identify due to their small size and similarities in morphology. Recently, in addition to morphology, both molecular and non-molecular taxonomic tools have been used to identify species differences. Insect cuticular hydrocarbons have been widely used in chemotaxonomy. In this study, a Thermal Separation Probe was used to identify the cuticular hydrocarbons of Frankliniella occidentalis, Frankliniella intonsa, Thrips palmi, Thrips hawaiiensis, Haplothrips chinensis and Gynaikothrips ficorum. We analyzed the hydrocarbon composition of adults in all 6 species, and in the larvae of F. occidentalis, T. hawaiiensis and T. palmi. The results showed that the composition of cuticular hydrocarbons differed between species. All 6 species of adults and 3 species of larvae were easily distinguishable by quantitative analysis of hydrocarbon profiles. These results provide a possible method for the identification of thrips.     

Lipophorin receptor regulates the cuticular hydrocarbon accumulation and adult fecundity of the pea aphid Acyrthosiphon pisum

Cuticular hydrocarbons form a barrier that protects terrestrial insects from water loss via the epicuticle. Lipophorin loads and transports lipids, including hydrocarbons, from one tissue to another. In some insects, the lipophorin receptor (LpR), which binds to lipophorin and accepts its lipid cargo, is essential for female fecundity because it mediates the incorporation of lipophorin by developing oocytes. However, it is unclear whether LpR is involved in the accumulation of cuticular hydrocarbons and its precise role in aphid reproduction remains unknown. We herein present the results of our molecular characterization, phylogenetic analysis, and functional annotation of the pea aphid (Acyrthosiphon pisum) LpR gene (ApLpR). This gene was transcribed throughout the A. pisum life cycle, but especially during the embryonic stage and in the abdominal cuticle. Furthermore, we optimized the RHA interference (RNAi) parameters by determining the ideal dose and duration for gene silencing in the pea aphid. We observed that the RNAi-based ApLpR suppression significantly decreased the internal and cuticular hydrocarbon contents as well as adult fecundity. Additionally, a deficiency in cuticular hydrocarbons increased the susceptibility of aphids to desiccation stress, with decreased survival rates under simulated drought conditions. Moreover, ApLpR expression levels significantly increased in response to the desiccation treatment. These results confirm that ApLpR is involved in transporting hydrocarbons and protecting aphids from desiccation stress. Furthermore, this gene is vital for aphid reproduction. Therefore, the ApLpR gene of A. pisum may be a novel RNAi target relevant for insect pest management.