The analysis of flight paths of male Egyptian cotton leafworm moths, Spodoptera littoralis, to a sex pheromone source in the field

ABSTRACT. The flight of male Spodoptera littoralis (Boisd.) (Noctuidae) towards a pheromone source was recorded during the early part of the night using a cine camera and an image intensifier. The cine films were analysed frame by frame to produce flight tracks from which it was possible to calculate the mean advance rate of moths towards the pheromone source and their projected ground speed, for a series of positions downwind of the source. As wind speed was measured the moth's air speed was also estimated. The moths compensated for changes in wind speed by varying their air speed, hence maintaining a ground speed independent of wind speed. The ground speed itself was found to decrease as moths flew closer to the pheromone source.     

Biosynthetic pathways of the pheromone of the Egyptian armyworm Spodoptera littoralis

Abstract Most insect pheromones comprise multicomponent blends of geometric or optical isomers, and one major question is how insects produce species‐specific ratios of components for successful reproductive isolation. Key enzymes suggested to be involved in pheromone biosynthesis are acetyl‐coenzyme A carboxylase and fatty acyl synthetase, chain‐shortening enzymes, desaturases, elongases, reductases, oxidases, and alcohol acetyl transferases. The female pheromone composition of the Egyptian armyworm Spodoptera littoralis (Boisd.) is highly dependent on the origin of the strain. In this review, we present a summary of the different reported pheromone compositions of the moth, including from our recent studies on this subject, as well as the biosynthetic routes to the different components and the molecular approaches involved. In addition, the key role played in the proposed biosynthetic pathways by a number of important biosynthetic enzymes, such as chain shortening enzymes, desaturases and alcohol acetyl transferases, is outlined, as well as the latest developments on the inhibition of these enzymes.     

Effect of the pheromone biosynthesis activating neuropeptide on sex pheromone biosynthesis in Spodoptera littoralis isolated glands

The control of Spodoptera littoralis sex pheromone biosynthesis has been investigated with synthetic pheromone biosynthesis activating neuropeptide (PBAN) and different labeled tracers using an in vitro isolated gland system. Responsiveness of the glands to PBAN stimulation was impaired by careless tissue manipulation. The fact that PBAN is active in the isolated gland system suggests that this might be a target organ for this peptide in S. littoralis. As reported previously with Br-SOG extracts and intact females, label incorporation into the pheromone increased in glands treated with PBAN from all the precursors tested. However, the formation of labeled intermediates from d₅E11–14:Acid also occurred in glands incubated in the absence of the peptide, but the amounts of d₅Z9, E11–14:Acid were lower in PBAN treated glands than in controls. These results indicate that PBAN controls pheromone biosynthesis in S. littoralis by regulating the reduction of acyl moieties. © 1994 Wiley-Liss, Inc.     

Effect of constant light on male sterility in the cotton leafworm Spodoptera littoralis

Females of the cotton leafworm (Spodoptera littoralis) reared in long day conditions (LD 16:8 h) and mated to males kept throughout the whole period of development in continuous light (LL) oviposit very small numbers of mostly sterile eggs. It was found that in control males reared from the first larval instar in long day conditions there was a large accumulation of euperene sperm bundles in their testes on day 1 after imaginal moult. On day 10 of adult life the number of the sperm bundles was very small. In males kept from the first instar in continuous light there was also high number of sperm bundles on day 1 after imaginal moult but it did not decrease significantly on day 10 as was observed in controls. Transfer of different developmental stages of S. littoralis from long day conditions to continuous light resulted in a big difference in the density of eupyrene sperm bundles in their testes. In control insects reared through the whole of their development in long day conditions there was a significant decrease in the density of eupyrene sperm bundles on day 10 of adult life. By contrast, in males in continuous light, regardless of their developmental stage when transferred, there was either no change in density of sperm bundles in day 10 adults or there was a significant increase in comparison with day 1 adults. The highest density of eupyrene sperm bundles was observed in day 10 adults when they were transferred to continuous light shortly before moulting to the last instar (as day 4 larvae in the last stadium or day 1 pupae). Generally, the density of eupyrene sperm bundles on day 10 of adult development was about 2–2.5 times higher in males in continuous light then those under long day conditions. The results presented here indicate that the last larval instar and the pupa are the stages most sensitive to constant light treatment, which greatly reduces the amount of eupyrene sperm bundles released from the testes.     

斜纹夜蛾在风洞中对性信息素的行为反应及田间诱捕试验

雌蛾腺体内含量最高的组份9,11-14∶Ac（A）在风洞中能引起雄蛾从搜索气迹、定向飞行到撒开味刷企图交尾连续的行为反应,而雌蛾腺体内其它组份单独使用时均不能引起雄蛾上述行为反应。一定量的Z9,E12-14∶Ac（B）对A的活性有增效作用,诱芯中B数量过多,不但失去对A的活性增效作用,还对雄蛾接近诱芯和企图交尾有强烈的抑制作用。9-14∶Ac（C）与11-14∶Ac (D)对雄蛾的定向行为无影响,诱芯中含有50%的C时,反而对雄蛾接近诱芯和企图交尾有抑制作用。A与B在滤纸诱芯中的含量比例与诱芯释放的挥发物比例明显不同,从9∶1（A∶B）诱芯释放的挥发物比例更接近于雌蛾腺体内的天然比例。田间诱捕试验中两组份诱芯的诱捕量随两组份比例不同而变化, 9∶1（A∶B）诱芯的诱捕量最大,1∶1（A∶B）诱芯的诱捕量低于单一的A组份诱芯。     

甜菜夜蛾对性信息素的行为反应及其田间诱捕效果

人工合成的甜菜夜蛾性信息素两组分（顺,反）-9,12-十四碳二烯醇醋酸酯（Z9,E12-14：Ac）和（顺）-9-十四碳烯醇（Z9-14：OH）按不同配比制成诱芯,在风洞中均能引起雄蛾搜索气迹、定向飞行及接近诱芯的行为反应.不同配比和剂量的诱芯诱虫效果差异显著（p＜0.05）.Z9,E12-14：Ac和Z9-14：OH按7：3配比,诱虫活性最高,表现在风洞中,搜索气迹、定向飞行和接近诱芯的蛾数最高,与处女蛾的引诱效果相当.以此配比制成的性诱剂在田间诱捕的虫量最多,与风洞的试验结果基本一致.诱芯剂量在0.05～0.5mg范围内均有显著的诱虫效果,但剂量过低或过高均导致诱捕率下降.同一配比诱芯在风洞中引起雄蛾接近诱芯的蛾量与田间诱蛾量呈显著相关（R1=0.968,R2=0.961）.并对这些结果在甜菜夜蛾田间性诱剂防治应用的前景进行了讨论.     

Functional characterization of sex pheromone receptors in Spodoptera frugiperda,S. exigua,and S. litura moths

Moths possess an extremely sensitive and diverse sex pheromone processing system, in which pheromone receptors (PRs) are essential to ensure communication between mating partners. Functional properties of some PRs are conserved among species, which is important for reproduction. However, functional differentiation has occurred in some homologous PR genes, which may drive species divergence. Here, using genome analysis, 17 PR genes were identified from Spodoptera frugiperda, S. exigua, and S. litura, which belong to 6 homologous groups (odorant receptor [OR]6, 11, 13, 16, 56, and 62); of which 6 PR genes (OR6, OR11, OR13, OR16, OR56, and OR62) were identified in S. frugiperda and S. exigua, and 5 PR genes were identified in S. litura, excluding OR62. Using heterologous expression in Xenopus oocytes, we characterized the functions of PR orthologs including OR6, OR56, and OR62, which have not been clarified in previous studies. OR6 orthologs were specifically tuned to (Z,E)-9,12-tetradecadienyl acetate (Z9,E12-14:OAc), and OR62 orthologs were robustly tuned to Z7-12:OAc in S. frugiperda and S. exigua. The optimal ligand for OR56 was Z7-12:OAc in S. frugiperda, but responses were minimal in S. exigua and S. litura. In addition, SfruOR6 was male antennae-specific, whereas SfruOR56 and SfruOR62 were male antennae-biased. Our study further clarified the functional properties of PRs in 3 Spodoptera moth species, providing a comprehensive understanding of the mechanisms of intraspecific communication and interspecific isolation in Spodoptera.     

Some physiological,biochemical and histopathological effects of Artemisia monosperma against the cotton leafworm,Spodoptera littoralis

The effect of Artemisia monosperma wild plant hexane extract on some biological and physiological aspects of Spodoptera littoralis, as well as some biochemical and histopathological changes after treatment with this extract have been studied. The results indicated that treatment with larvae for two days revealed satisfactory effects in larval mortality (50%) and in larval weight and prolonged the effect in the pupal stage. Also the treatment reduced the food consumption and the amount of faeces of the tested larvae which led to a significant reduction in the final body weight with 76.4%. Treatment also extended the time of food passage through the midgut to 3.2 h compared to 1.38 h in control, and the larvae had a smaller midgut. The enzymatic activity of the digestive enzymes amylase and invertase revealed a significant inhibition in the treated larvae. Also transaminase enzyme activity (AST and ALT) reduced after treatment. The results of phosphatase enzyme activity (ACP and ALP) showed a potent inhibitory effect on both enzymes which more was pronounced in ALP than ACP activity, the percent inhibition being 73.8% and 30.6%, respectively. The histopathological effects of A. monosperma treatment on the midgut of Spodoptera littoralis revealed that the epithelium membrane was exfoliated and completely destroyed. Meanwhile, epithelia cells were strongly vacuolated and considerably elongated. Boundary lines between the cells disappeared.     

The effects of pheromone concentration on the flight behaviour of the oriental fruit moth, Grapholitha molesta

ABSTRACT. Male oriental fruit moths, Grapholitha molesta (Busck) (Tortricidae), flew at lower overall and net ground velocities when they flew toward higher concentration pheromone sources. Turning frequency was greater with increased pheromone concentration, while the distance of turns from the plume axis back towards the axis decreased. Turning magnitude and inter-reversal track angles remained constant at all concentrations tested. Concomitant with the changes in ground velocity but constant inter-reversal angles, were decreases in airspeed, decreases in the moths' course angles and increases in their drift angles. The significance of these changes is discussed in relation to their possible role in a longitudinal chemoklinotactic programme of turning operating in conjunction with anemotaxis to allow location of a pheromone source in wind.     

Behavioral responses of maleHeliothis armigera (Lepidoptera: Noctuidae) moths in a flight tunnel to combinations of components identified from female sex pheromone glands

Six compounds were identified from gland extracts of the cotton bollworm, Heliothis armigera(Hubner): (Z)-11-hexadecenal (Z11-16:Ald), (Z)-9-hexa-decenal (Z9-16:Ald), hexadecanal, (Z)-11-hexadecenol (Z11-16:OH), (Z)-7-hexadecenal (Z7-16:Ald), and (Z)-9-tetradecenal (Z9-14:Ald). Each of the compounds that were identified was examined for its ability to elicit sexual responses from male moths in a flight tunnel. Males flew upwind to Z11-16:Ald alone, but greater levels of copulatory responses were evoked with the addition of 2.5% Z9-16:Ald to the Z11-16:Ald. Addition of hexadecanal to the binary mixture had no effect in raising the behavioral response of the males in the flight tunnel. The effect of Z7-16:Ald on male flight depended on the loading. The addition of 1% of this component to 2 mg of the binary mixture reduced levels of copulatory response, but the same addition (1 %) to 10 g of the binary mixture increased copulatory response. The addition of 79-14:Ald or Z11-16:OH to the binary mixture reduced behavioral responses of males. High loadings of the binary mixture (200–2000 g) were better than a low loading (10 g) in eliciting response of males.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 2455-E, 1988 series.     

Disruption of male spruce budworm orientation to female moths by pheromone and pheromone analogues in a wind tunnel

Abstract. The ability of male spruce budworm moths, Choristoneura fumiferana (Clem.), to orientate to and locate virgin female moths was investigated in a laboratory wind tunnel. When presented with two caged ‘target female’ moths, more than 99% of the male moths locked on and flew directly to the females. When confined for 3 h before release, downwind of a three-dimensional array of thirty-five evenly distributed female moths (a density of 40/m³), over 90% of the males still successfully oriented to one or another of the females, although not always to the target females. With an array of thirty-five septa containing either E-11-tetradecenyl acetate on E-11-tetradecenol there was no visible change in behaviour; >90% of the males flew directly to the two target females, which indicates that neither the acetate nor the alcohol has potential for mating disruption. An array of thirty-five septa containing a 955 blend of E- and Z-11-tetradecenal, the main components of the spruce budworm sex pheromone, significantly reduced the numbers of male moths able to locate the target females, and effects were concentration-dependent. The highest concentration, which gave a release rate similar to that of a calling female, produced the same level of disruption as the thirty-five females, but sensory fatigue became a factor in addition to ‘false trail following’. Lower concentrations were significantly less effective, with no evidence of sensory fatigue. At all concentrations significant numbers of males flew to the septa (false trail following), but when male moths were left uncaged in the tunnel for a further 3h, most eventually located the females. This suggests that false trail following alone will not prevent mating. The level of disruption was not improved by the addition of 2% tetradecanal to the 955 blend. Similar levels of disruption to the 955 blend were obtained with an 80:20 blend. A 5050 blend still caused a significant amount of false trail following, but less than the other blends. The ability of male spruce budworm to orientate to off-blend trails was enhanced if the males were first exposed to the natural, female-produced pheromone.     

Sexual behaviour and pheromone titre of the Spodoptera littoralis female moth

The sexual behaviour of females of the Egyptian cotton leafworm, Spodoptera littoralis (Boisduval), was studied in the laboratory. Calling of females was maximal on the 2–3rd night between 3 and 9 h into scotophase. Largest amounts of pheromone were found in the glands of 1–3 day-old 2–3 h into scotophase: a maximum of 6–8 ng of (Z,E)-9,11-tetradecadienyl acetate per female. Very low amounts of pheromone were detected 1 h before and at the end of scotophase. Mating of 2–3 day-old females, occurred mainly between 0 and 3 h into scotophase. Mating suppressed the pheromone titre drastically when measured 3 h after copulation but the titre increased significantly after 24 h, prior to egg laying. However, when egg laying commenced, the amount of pheromone detected was negligible. A high concentration of synthetic pheromone in closed containers did not affect calling of females. On the other hand mating was drastically suppressed in a pheromone-permeated atmosphere.

---

Zusammenfassung Das Sexualverhalten der Weibchen des ägyptischen Baumwollwurms, Spodoptera littoralis (Boisduval) wurde unter Laborverhältnissen untersucht. Das maximales Rufen der Weibchen war in der 2–3 Nacht zwischen 3 und 9 Stunden der Skotophase. Die grössten Pheromonmengen wurden in den Drüsen der 1 bis 3 Tage alten nach 2–3 Stunden in der Skotophase gefunden und zwar maximal 6–8 ng (Z,E)-9,11-Tetradecadienyl Acetate. Ein drastischer Abfall des Pheromoninhalts wurde zwischen der 4 und 5 Nacht beobachtet. Sehr kleine Pheromonmengen wurden eine Stunde vor der Skotophase und nach ihrem Ablauf gefunden. Die Paarung 2–3 Tage alten wurde im allgemeinen zwischen Stunden 0 und 3 der Skotophase beobachtet. Drei Stunden nach der Paarung war der Pheromontiter drastisch herabgesetzt, er stieg jedoch nach 24 Stunden, vor der Eiablage bedeutend an. Sobald die Eiablage anfing, war das Pheromon jedoch kaum nachweisbar. Eine hohe Konzentration des synthetischen Pheromons in geschlossenen Gefässen beeinflusste das Rufen der Weibchen nicht. Anderseits war jedoch die Paarung in einer mit Pheromon durchgedrungenen Atmosphäre sehr stark herabgesetzt.

     

The effects of unilateral antennectomy on the flight behaviour of male Heliothis virescens in a pheromone plume

Abstract .Unilaterally antennectomized Heliothis virescens (F.) males flying close to the central axis of a plume of sex pheromone display no significant differences in behaviour compared to sham-operated males in course angles, track angles, airspeed and groundspeed. This demonstrates that right/left antennal information is not necessary for normal orientation movements in response to pheromone, but rather that it is 'blended' within the moth's central nervous system before pheromone-mediated manoeuvres are made. However, some unilaterally antennectomized moths (36%) make repetitive, asymmetrical, saw-tooth-shaped tracks during pheromone-mediated upwind progress, whereas control moths never make such tracks. Unilaterally antennectomized moths made such tracks on the side of the plume contralateral to the missing antenna. We hypothesize that these occasional asymmetrical tracks in unilaterally ablated males are the result of reiterative asymmetrical pheromone stimulation of a higher probability on track legs going toward rather than away from the long axis of the plume on males with a single antenna remaining on the 'away from axis' side. Combined with a greater propensity for treated moths to lock onto the plume away from the central axis on one side rather than the other, repetitive successive asymmetrical track legs (resulting in a saw-tooth-shaped track) are commonly observed in these moths. Control moths do also make asymmetric successive track legs but they rarely are repeated and thus are not readily observed.     

性信息素对斜纹夜蛾雄蛾嗅觉相关基因 abp,pbp 和 or 表达的影响

【目的】信息素是个体之间传递信息的重要分子,研究性信息素对斜纹夜蛾 Spodoptera litura 嗅觉相关基因表达的影响对于增加性信息素作用机理的认识及其应用有重要的意义。【方法】本研究通过实时定量PCR（qRT-PCR）技术探究在性信息素刺激处理条件下,斜纹夜蛾成虫嗅觉相关基因 abp, pbp 和 or 表达水平的变化;利用性信息素在田间诱捕斜纹夜蛾雄蛾,并通过自动计数器记录每小时诱虫量,从而间接显示其交配行为的节律性。【结果】斜纹夜蛾雄虫触角中嗅觉相关基因abp, pbp 和 or 的表达具有节律特性。经性信息素化合物(Z9, Z11-14:OAc+Z9, Z12-14:OAc)刺激处理后,abp, pbp 和 or 表达量也发生了显著的改变。通过记录田间性信息素诱捕器在一天中不同时间段内诱捕的雄蛾数量,发现诱捕到的斜纹夜蛾也具有节律特性。【结论】基因表达水平上的节律特性可能与雄虫交配活动的节律相关联,说明性信息素处理也在一定程度上改变了其节律及其对性信息素的神经反应。这一结果也首次从基因水平证明性信息素的刺激处理提高了周缘神经系统对性信息素反应的敏感性,有助于我们理解性信息素作用的分子机理,对迷向及性诱和测报应用具有指导意义。     

Inhibitory effect of 10,11-methyl-enetetradec-10-enoic acid on a Z9-desaturase in the sex pheromone biosynthesis of Spodoptera littoralis

The effect of 10,11-methylenetetradec-10-enoic acid on the sex pheromone biosynthetic pathway of Spodoptera littoralis is reported. This new cyclopropene fatty acid inhibited the biosynthesis of the main pheromone component from labeled myristicacid. The study of each Z desaturation step revealed that the Z9-desaturase of E11–14:Acid was inhibited, whereas the Z11-desaturase of 16:Acid was not affected. The results presented in this article agree with our hypothesis that the methylenehexadecenoic acids are beta-oxidized in the pheromone gland to the corresponding methylenetetradecenoic acids. © 1994 Wiley-Liss, Inc.     

斜纹夜蛾性信息素诱捕器田间应用技术

考查斜纹夜蛾Spodoptera litura(Fabricius)性信息素诱捕器放置高度、间隔距离以及气象因子对性信息素诱集效果的影响。结果表明,放置高度为1m时,性信息素诱捕器易引起斜纹夜蛾的反应,明显优于0.5m和1.5m的诱集效果。诱捕器放置的间隔距离,以25m为诱集效果最佳,与10,15,20及30m的具有显著差异。夜间风向对诱捕器的诱蛾效果具有明显影响,在3个成一列放置的诱捕器中,诱集量最大的是放在上风口位置的诱捕器;同时,与夜间风向平行设置的诱捕器,其诱集量显著高于与夜间风向垂直设置诱捕器的诱集量。     

Hickory shuckworm Cydia caryana: electroantennogram and flight tunnel studies of potential sex pheromone components

Electroantennogram (EAG) measurement of male Cydia caryana moth antennal olfactory response to monounsaturated 12 and 14 carbon alcohols and acetates indicated that the (E)-8-, (E)-10- conjugated double bond system of a dodecadien-1-ol acetate is a critical chemical structural component of the C. caryana sex pheromone. Additionally, EAG measurements implicated (E)-8-dodecen-1-ol acetate, (Z)-8-dodecen-1-ol acetate, (Z)-9-dodecen-1-ol acetate and (Z)-12-tetradecen-1-ol as potential minor pheromonal components. An EAG dosage-response study suggested that there were at least two heterologous populations of pheromone acceptors. Behavioral analysis of male moth response in a flight tunnel to compounds which evoked the stronger EAG responses suggested that (E,E)-8,10-dodecadien-1-ol acetate and (Z)-9-dodecen-1-ol acetate resemble or are C. caryana sex pheromonal components, while (Z)-8-dodecen-1-ol acetate and (E)-10-dodecen-1-ol acetate are either parapheromones or are minor pheromone components. Behavioral significance of (Z)-12-tetradecen-1-ol was difficult to interpret in the flight tunnel.

---

Résumé Les réponses olfactives antennaires de Cydia caryana, mesurées par électroantennogrammes (EAG), aux alcools et acétates à carbones monounsaturés en positions 12 et 14, ont montré que le système conjugué de double liaison, (E)-8-, (E)-10- du dodecadien-1-ol acétate constitue un composé chimique strutural critique de la phéromone sexuelle de C. caryana.De plus, les acétates: (E)-8-dodecen-1-ol,(Z)-8-dodecen-1-ol,(Z)-9-dodecen-1-ol, et le (Z)-12-tetradecen-1-ol, se sont révélés en AEG comme des composés secondaires de la phéromone. L'étude par AEG de la relation dose-réponse a conduit à l'hypothèse de deux catégories de populations de récepteurs de phéromones. L'analyse comportementale des résponses des papillons mâles dans le tunnel de vol aux composés qui ont provoqués les plus forts AEG, on fait estimer que les acétates (E,E)-8,10-dodécadien-1-ol et (Z)-9-dodecen-1-ol ressemblent (ou sont) les constituants de la phéromone sexuelle de C. caryana; tandis que les (Z)-8-dodecen-1-ol et (E)-10-dodecen-1-ol sont, soit des paraphéromones, soit des constituants mineurs de la phéromone.La signification biologique du (Z)-12-tétradécen-1-ol a été difficile à interprêter avec les expériences en tunnel de vol.

     

Peripheral regulation by ecdysteroids of olfactory responsiveness in male Egyptian cotton leaf worms, Spodoptera littoralis

Physiological and behavioral plasticity allows animals to adapt to changes in external (environmental) and internal (physiological) factors. In insects, the physiological state modulates adult behavior in response to different odorant stimuli. Hormones have the potential to play a major role in the plasticity of the olfactory responses. To explore if peripheral olfactory processing could be regulated by steroid hormones, we characterized the molecular, electrophysiological, and behavioral response to changes in endogenous hormone levels in adult male Spodoptera littoralis. The expression of the receptor complex (EcR/USP) was localized by in situ hybridization in the olfactory sensilla of antennae. Injections of 20-hydroxyecdysone (20E) induced an ecdysteroid signaling pathway in antennae and increased expression of the nuclear receptors EcR, USP and E75. Diacylglycerol kinase (DGK) and CaM expression were also up-regulated by 20E. Taken together, these molecular, electrophysiological, and behavioral results suggest a hormonal regulation of the peripheral olfactory processing in S. littoralis.     

Scoliopteryx libatrix (L.) (Lep., Noctuidae) male reaction to the synthetic main sex pheromone component and its isomers – wind tunnel and field investigations

Abstract: The four stereoisomers of 6,13-methylheneicosene were tested with Scoliopteryx libatrix (L.) males in a wind tunnel. The most active isomer was (Z6,S13)-methylheneicosene which had been identified as the main sex pheromone component of the species. Some medium activity was found for (Z6,R13)- and (E6,S13)-, while the (E6,R13)-stereoisomer showed the lowest activity. These results were confirmed in field tests with sticky traps. Monitoring of S. libatrix at two sites showed that the flight of the insects started at the end of March to the beginning of April and lasted till August to the beginning of September. It was concluded that the males of the second generation were not attracted by the pheromone.