Diel periodicity and influence of age and mating on female sex pheromone titre in Estigmene acrea (Lep., Arctiidae)

Abstract:  Calling behaviour, diel periodicity, and effect of age and mating on female sex pheromone titre in Estigmene acrea (Drury) were studied under laboratory conditions. Forty-five per cent of females started calling during the first scotophase, but the highest number of calling females was observed during the second, third and fourth scotophases. Calling behaviour occurred from the third hour after dark until just before the end of the scotophase. However, females exhibited a bimodal pattern of calling with the first peak occurring between 4 and 6 h and a second peak at 10 h after the onset of scotophase. The mean onset of calling time differed significantly with age. Older females showed a tendency to call longer, but there was no significant difference. The amount of (Z,Z)-3,6-cis-9, 10-epoxyheneicosadiene in females was quantified from the first scotophase following emergence, until the fifth scotophase. Glands of 0-day-old females presented a higher content of pheromone compared with that found in glands of 1-, 2-, 3- and 4-day-old females. Pheromone titre was determined at 2-h intervals throughout the third scotophase and photophase. (Z,Z)-3,6-cis-9,10-epoxyheneicosadiene was found in the gland during the scotophase as well as the photophase. However, there was no consistent pattern of pheromone production throughout the scotophase or photophase. Mated females of E. acrea produced significantly less pheromone than virgin females.     

枣镰翅小卷蛾性信息素通讯系统

采用单个雌蛾性信息素腺体分析技术对枣镰翅小卷蛾Ancylis sativa Liu雌蛾性信息素的组分和组分间的精确比例进行了测定,结果表明,枣镰翅小卷蛾雌蛾的性信息素系统由二个顺反异构体组分组成,即反-9-十二碳烯醋酸酯(E9-12∶Ac)和顺-9-十二碳烯醋酸酯(Z9-12∶Ac)组成,E9-12∶Ac与Z9-12∶Ac的比例为6.5∶3.5;雌蛾产生和释放性信息素具有时辰节律性,在光周期14L∶10D、温度为21℃时,性信息素产生的高峰期为进入黑暗期6.5 h;不同日龄雌蛾产生的性信息素有差异,1日龄最低,2日龄最高,3～5日龄居中,不同日龄雌蛾产生的性信息素组分间的比例无显著差异;对3个世代雌蛾产生的性信息素的量及组分间的比例的研究表明,越冬代含量最高,为(10.1±7.0)ng/头,第2代为(9.5±4.6)ng/头,第1代仅为(1.4±1.0)ng/头,3个世代性信息素组分间的比例无显著差异,在63.1%～64.3%(E)范围内。     

笋秀夜蛾雄蛾对性信息素化合物的电生理和行为反应

利用气质联用仪对笋秀夜蛾雌蛾性腺体粗提物成分进行了分析比对,通过触角电位(EAG)试验研究了笋秀夜蛾雄成虫对性信息素组分的电生理反应,以Y形嗅觉仪进行了室内和林间的行为生测.结果表明： 雌蛾性腺体粗提物中顺11-十六碳乙酸酯(Z11-16:Ac)和顺11-十六碳烯醇(Z11-16:OH)为笋秀夜蛾性信息素活性组分,性腺粗提物、两种化合物及其混合物均能激发雄蛾明显的EAG反应,且EAG反应值随性信息素组分浓度增加而增加.Z11-16:Ac和Z11-16:OH按57∶43配置成的二元混合物所激发的EAG反应强于同等剂量下的单一组分.室内的行为生测和林间诱捕试验结果与EAG反应基本一致,Z11-16:Ac+Z11-16:OH(57∶43)混合物对雄蛾引诱力最强,在林间单诱捕器(诱芯浓度为10⁴ng·μL^-1)的平均诱捕量达到(48.5±6.7)头.     

Selection for altered pheromone-component ratios in the pink bollworm moth,Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Female pink bollworm moths, Pectinophora gossypiella(Saunders), were selected for altered component ratios of the long-distance sex pheromone, (Z, E)-and (Z, Z)-7,11- hexadecadienyl acetate. Selection for 12 generations increased the mean (± SD) percentage of the (Z, E)isomer from 42.9 ± 1.0 in the parental generation to 48.2 ± 1.2. Although statistically significant, a change of this magnitude may be transparent to males because of their relatively broad response spectrum. Selection for a lower percentage of the (Z, E)isomer yielded no change in the mean pheromone ratio. The total amount of pheromone produced declined in both selected lines. In the line selected for females producing a high percentage of the (Z, E)isomer, the duration of wing fanning by males to high (Z, E)blends was elevated.     

EFFECTS OF SUBLETHAL ESERINE ON THE CHEMICAL COMMUNICATION SYSTEM OF ASIAN CORN BORER,OSTRINIA FURNACALIS (GUENEE)*

Abstract Topically applied sublethal doses of eserine may interrupt chemical communication between the two sexes of Asian corn borer, Ostrinia furnacalis (Guenee), by affecting calling and sex pheromone titre released by the females. (1) Studies on the effects of sublethal eserine on the chemical communication system of O. furnacalis indicated that there was a decreasing probability of females calling and sex pheromone titre as the eserine dosage increased from 0.27 to 2 700 ng, with no effect on the periodicity. However, at 2 700 ng, the E/Z ratio of the sex pheromone components was affected. The sexual chemical communication system could not control within narrow level. (2) The recovery test of 27ng‐treated female indicated that the calling percentages of the 1st, 2nd and 4th day post‐treatment were 50%, 78% and 84% respectively. Sex pheromone titre was 40%, 40% and 80% of control female repectively. There was a trend toward recovery. The sexual chemical communication system could control within narrow level from the 2nd day post‐treatment.     

Activity of the diastereoisomers of 13,23-dimethylpenta-triacontane, the sex pheromone of Glossina pallidipes, and comparison with the natural pheromone

ABSTRACT. All three synthetic diastereoisomers of 13,23-dimethyl-pentatriacontane, the pheromone of Glossina pallidipes (Austen), have been tested in the G. pallidipes sex pheromone bioassay, together with one of the four diastereoisomers of 13,17-dimethylpentatriacontane, originally proposed as a candidate pheromone of G. pallidipes. Of the three isomers of 13,23-dimethylpentatriacontane only the (13R,23S) isomer was active with an ED-50 of 4.47±1.09/μg (mean±SD). The (13R,17R)-13,17-dimethylpentatriacontane was inactive. The diastereo-isomeric mixtures of 13,17- and 13,23-dimethylpentatriacontane were active with ED-50 values of 17.88±1.25/μg and 8.88±1.15μg respectively. The natural pheromone was active with an ED-50 of 8.07±1.17 μg indicating it to be a diastereoisomeric mixture.     

Within-population variability in a moth sex pheromone blend: genetic basis and behavioural consequences

Evolutionary diversification of sexual communication systems in moths is perplexing because signal and response are under stabilizing selection in many species, and this is expected to constrain evolutionary change. In the moth Heliothis virescens, we consistently found high phenotypic variability in the female sex pheromone blend within each of four geographically distant populations. Here, we assess the heritability, genetic basis and behavioural consequences of this variation. Artificial selection with field-collected moths dramatically increased the relative amount of the saturated compound 16:Ald and decreased its unsaturated counterpart Z11–16:Ald, the major sex pheromone component (high line). In a cross between the high- and low-selected lines, one quantitative trait locus (QTL) explained 11–21% of the phenotypic variance in the 16:Ald/Z11–16:Ald ratio. Because changes in activity of desaturase enzymes could affect this ratio, we measured their expression levels in pheromone glands and mapped desaturase genes onto our linkage map. A delta-11-desaturase had lower expression in females producing less Z11–16:Ald; however, this gene mapped to a different chromosome than the QTL. A model in which the QTL is a trans-acting repressor of delta-11 desaturase expression explains many features of the data. Selection favouring heterozygotes which produce more unsaturated components could maintain a polymorphism at this locus.     

Canalization of the redbanded leafroller moth sex pheromone blend

Previous attempts to shift the (Z)-11-/(E)-11-tetradecenyl acetate ratio of pheromone components in the redbanded leafroller moth (RBLR), Argyrotaenia velutinana, by several selection protocols showed that this ratio is strongly canalized. Analysis of the complete seven-component blend, however, showed that a Geneva laboratory stock of RBLR had a lower percent (20%) of the E9–12:OAc minor component compared to the E11–14:OAc component than a population of RBLR from North Carolina (31%). Hybrid populations from these two cultures were used in a two-way family truncation selection scheme in which families were selected for either the lowest (low line) or the highest (high line) ratio of E9–12:OAc/E11–14:OAc. After three generations of selection, the low line had 14% E9–12:OAc relative to E11–14:OAc and the high line had 42%. The selection pressure was removed in generations 4–9, and the low line remained unchanged at 14% E9–12:OAc; but in the high line, it drifted to 53%. Studies were conducted to estimate heritability and realized heritability. The realized heritability calculated for each generation of selection averaged 1.14 for the low line and 1.50 for the high line. These calculations, along with estimated heritability values of 0.416 and 0.644 for reciprocal crosses, indicate some plasticity in the E9–12:OAc/E11–14:OAc ratio. This ratio was positively correlated to the total amount of 12-carbon components to 14-carbon components, but was negatively correlated to the Z/E ratio of Δ11-tetradecenylacetates. The results of two studies on the canalization of various components of the RBLR sex pheromone blend indicate that there is limited potential in this insect for manipulation of the blend ratios in the laboratory.     

Sex pheromone of the butterbur borer, Ostrinia zaguliaevi

The sex pheromone blend of the butterbur borer, Ostrinia zaguliaevi (Lepidoptera: Pyralidae) was analyzed by means of gas chromatography-electroantennographic detection (GC-EAD), GC-mass spectrometry and a series of wind-tunnel bioassays. Four EAD-active compounds were detected in the female sex pheromone gland extract, and these were identified as tetradecyl acetate (14:OAc), (Z)-9-tetradecenyl acetate (Z9-14:OAc), (E)-11-tetradecenyl acetate (E11-14:OAc) and (Z)-11-tetradecenyl acetate (Z11-14:OAc). The average amounts ± s.d. of the four compounds in a single sex pheromone gland were 7.9±3.7 ng, 10.1±3.2 ng, 1.1±0.5 ng and 11.6±5.1 ng, respectively. In a wind-tunnel bioassay, the ternary blend of Z9-, E11- and Z11-14:OAc at a ratio found in the sex pheromone gland (45:5:50) elicited the same behavioral responses from the males as did virgin females and pheromone gland extract. Removal of any single compound from the ternary blend significantly diminished the pheromonal activity, whereas addition of 14:OAc to the ternary blend had no effect on the males' behavioral responses. Therefore, it was concluded that the sex pheromone blend of O. zaguliaevi is composed of Z9-14:OAc, E11-14:OAc and Z11-14:OAc at a ratio of 45:5:50.     

Effect of (E4, Z6)-4,6-Hexadecadienal in attraction of Stathmopoda masinissa with its pheromone components of Korean population

Timely insecticidal application for Stathmopoda masinissa Meyrick (Lepidoptera: Stathmopodidae), is important, for reducing damage to persimmon (Diospyros kaki Thunb.), an important tree fruit cultivated in Korea. In this regard, the early and precise detection of adult S. masinissa is desirable. In this study, we report the effect of (E4,Z6)-4,6-hexadecadienal (E4,Z6-16Ald) with sex pheromone components in attracting S. masinissa males. The sex pheromone of S. masinissa in the Korean population comprised two components, (E4,Z6)-4,6-hexadecadienyl acetate (E4,Z6-16Ac) and (E4,Z6)-4,6-hexadecadienol (E4,Z6-16OH). It was shown that the E4,Z6-16Ald acts as a synergist of E4,Z6-16Ac for attracting S. masinissa in the Japanese population. To test whether E4,Z6-16Ald could be used as an attractant in the Korean population, the E4,Z6-16Ald with the two pheromone components was evaluated in attracting S. masinissa males. Electroantennography (EAG) assays were performed to determine the antennal responses of S. masinissa males to the two pheromone components and E4,Z6-16Ald tested. A field attraction test with a combination of pheromones and E4,Z6-16Ald was carried out for 3 years in three different regions in Korea. E4,Z6-16Ald elicited as high a response as the two pheromone components. A mixture of the two pheromone components and E4,Z6-16Ald and a mixture of E4,Z6-16Ac and E4,Z6-16Ald attracted more S. masinissa males than a mixture of E4,Z6-16Ac and E4,Z6-16OH, the pheromone of Korean population. This new pheromone lure formulation with E4,Z6-16Ald is expected to contribute to the precise detection of S. masinissa by luring males to pheromone-baited traps.     

Kairomonal effect of sex pheromone components of two lepidopteran olive pests on Trichogramma wasps

Egg parasitoids are known to use a wide range of chemicals, emitted by plants, host eggs or adults, for host selection. The effect of the sex pheromone components of the lepidopteran olive pests Prays oleae (Lepidoptera: Yponomeutidae) and Palpita unionalis (Lepidoptera: Pyralidae) was studied under laboratory conditions, on the foraging behaviour of the egg parasitoid Trichogramma oleae (Hymenoptera: Trichogrammatidae). The response of T. oleae wasps to ( Z )-7-tetradecenal and ( E )-11-hexadecenal, major sex pheromone components of P. oleae and P. unionalis respectively, depended on the dose of the pheromone used in a Y-tube olfactometer bioassay. ( E )-11-hexadecenal elicited maximum attraction (70%) at a dose of 1 μg, while a dose of 100 μg ( Z )-7-tetradecenal attracted 80% of the tested wasps. ( E )-11-hexadecenyl acetate, the second sex pheromone component of P. unionalis , and the binary blend of ( E )-11-hexadecenyl acetate: ( E )-11-hexadecenal (7:3) were not attractive at these doses. The results of this research are discussed in view that they may be considered as alternatives in the biological control of these pests.     

Orientation disruption of Planotortrix octo using pheromone or inhibitor blends

Orientation disruption (indicated by reduced trap catch) of adult male Planotortrix octo (Lepidoptera: Tortricidae) was examined in eight small plot trials at four apple orchards over three years, using either (i) Z5-14:OAc (inhibitor), (ii) a blend of 25:75 Z5-14:OAc and Z8-14:OAc (inhibitor plus partial pheromone), or (iii) 50:50 Z8-14:OAc and 14:OAc (pheromone) in polyethylene rope dispensers at 100 or 200 dispensers per 0.1 ha. Use of inhibitor plus partial pheromone gave significant reductions in trap catch in all eight trials. Inhibitor alone gave statistically significant reductions in catch in all three trials where it was tested, but was not as effective as the inhibitor plus partial pheromone in one of these trials. Three trials comparing efficacy between the pheromone and the inhibitor plus partial pheromone blend showed no difference between these blends. Analysis of covariance of trap catch after treatment, using the catch in the first generation in each trap as a covariate, was useful for detection of treatment effects. Traps containing the blend of Z5-14:OAc and Z8-14:OAc were not attractive, suggesting that false trails may not be important where this blend is used, since it is an incomplete pheromone and contains an inhibitor.Disruption of mating was examined in closed containers, with dispensers containing (i), or (ii). Mating frequency was 86.4% in the controls, compared to only 14.3% with the inhibitor present alone, or 1.7% with partial pheromone and inhibitor. The frequency of mating in scotophase within 1–8 h after termination of 24 h exposure to a very high dose of the non-attractive blend of 25%:75% Z5-/Z8-14:OAc was identical for treated and untreated P. octo males.     

Elevated temperature increases reproductive investment in less preferred mates in the invasive European corn borer moth

Rapidly changing environments may weaken sexual selection and lead to indiscriminate mating by interfering with the reception of mating signals or by increasing the costs associated with mate choice. If temperature alters sexual selection, it may impact population response and adaptation to climate change. Here, we examine how differences in temperature of the mating environment influence reproductive investment in the European corn borer moth (Ostrinia nubilalis). Mate preference in this species is known to be related to pheromone usage, with assortative mating occurring between genetically distinct E and Z strains that differ in the composition of female and male pheromones. We compared egg production within and between corn borer lines derived from four different populations that vary in pheromone composition and other traits. Pairs of adults were placed in a mating environment that matched the pupal environment (ambient temperature) or at elevated temperature (5°C above the pupal environment). At ambient temperature, we found that within‐line pairs produced eggs sooner and produced more egg clusters than between‐line pairs. However, at elevated temperature, between‐line pairs produced the same number of egg clusters as within‐line pairs. These results suggest that elevated temperature increased investment in matings with typically less preferred, between‐line mates. This increased investment could result in changes in gene flow among corn borer populations in warming environments.     

(Z)-9-tetradecenal: a potent inhibitor of pheromone-mediated communication in the oriental tobacco budworm moth,Helicoverpa assulta

The behavioural significance of (Z)-9-tetradecenal to male H. assulta was tested by comparing the number of moths attracted to lures containing a standard synthetic female sex pheromone with lures in which (Z)-9-tetradecenal was also added. The standard pheromone mixture used contained 1000 g (Z)-9-hexadecenal, 50 g (Z)-11-hexadecenal, 300 g (Z)-9-hexadecenyl acetate and 15 g (Z)-11-hexadecenyl acetate impregnated on rubber septa. Addition of (Z)-9-tetradecenal to the standard pheromone was shown to significantly reduce the caught of male H. assulta when added in amounts greater than 10 g or 1% of the major pheromone component in both field and net-house experiments. The reduction in catch was found to be dependent on the quantity of (Z)-9-tetradecenal added to the standard pheromone. The implications of these results on conspecific and inter-specific pheromone-mediated communication in H. assulta and related sympatric heliothine species is discussed.Abbreviations Z9-16:AL (Z)-9-hexadecenal - Z11-16:AL (Z)-11-hexadecenal - Z9-16:AC (Z)-9-hexadecenyl acetate - Z11-16:AC (Z)-11-hexadecenyl acetate - Z9-14:AL (Z)-9-tetradecenal - Z9-16:OH (Z)-9-hexadecen-1-ol - Z11-16:OH (Z)-11-hexadecen-1-ol - RH relative humidity     

Effect of a neuroendocrine factor on sex pheromone biosynthesis in the tomato looper,Chrysodeixis chalcites (Lepidoptera: Noctuidae)

The presence of a pheromone biosynthesis activating neurohormone in the head gandlia, and its effect on the sex phermone biosynthetic pathway, were investigated in the tomato looper, Chrysodeixis chalcites (Esper). Comparison of pheromone components and precursor levels in the presence and absence of the factor was performed using untreated, ligated and ligated and injected virgin females. Pheromone glands of treated and untreated moths were extracted and analyzed by capillary gas chromatography for their most abundant pheromone components, (Z)-7-dodecenyl acetate and (Z)-9-tetradecenyl acetate, and the putative biosynthetic precursors hexadecanoate, (Z)-11-hexadecenoate, (Z)-9-tetradecenoate and (Z)-7-dodecenoate. Comparison of the amounts of the pheromone and precursor components in the three groups of females indicated that a neuroendocrine factor is involved in the regulation of the pheromone biosynthesis in C. chalcites. Lack of such a factor resulted in a marked decrease of the sex pheromone components as well as the three unsaturated putative biosynthetic precursors. However, no decrease was observed in the content of palmitoate, suggesting that the Δ11 desaturation step is affected by the neuroendocrine factor. Injection of head ganglia extracts into ligated females resulted in a recovery of unsaturated precursor and phermone content. Both male and female head ganglia were found to contain a sex pheromone biosynthesis regulatory factor. However, the stimulatory pattern of the factor from the two sexes was different, suggesting that the two factors are quantitatively and/or qualitatively distinct.     

Measurement by electroantennogram of airborne pheromone in cotton treated for mating disruption of Pectinophora gossypiella following removal of pheromone dispensers

The presence of pheromone in cotton foliage after removal of pheromone dispensers was assessed by measuring the airborne pheromone concentration with an electroantennogram device. Plots of 0.4 ha in isolated cotton fields were treated with Shin-Etsu PBW-Rope® pheromone dispensers for mating disruption of Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae). The dispensers contained ( Z , Z )- and ( Z , E )-7,11-hexadecadienyl acetates (gossyplure) in a 49:51 ratio and were applied at a density of 1 000/ha. The 400 pheromone dispensers were removed 1–12 days later. In four experiments involving canopy heights from 30–150 cm, the decay of the pheromone concentration was recorded repeatedly in short intervals for up to 7 h. Decay to undetectable concentrations generally occurred within 1–10 h, depending on plant size and wind conditions. In all four experiments, pheromone concentration 24 h after removal was found to be near or below detection threshold of the electroantennogram. The presence of pheromone within and above the cotton after dispenser removal would be due to re-entrainment of pheromone that had been adsorbed on cotton foliage or possibly some residual airborne pheromone.     

Sulfhydryl-reagent inhibition of olfaction in a moth and effects of exposure to pheromone compounds or a pheromone analogue

The effects on olfaction of N-ethylmaleimide (NEM), a specificreagent of free sulfhydryl groups, were studied in the mothMamestra brassicae. The antennae of male M.brassicae bear twotypes of specialist receptor neurons involved in pheromone communication.One type is tuned to (Z)-11-hexadecenyl acetate (Z11-16:Ac),the main pheromone component; the second type is tuned to (Z)-9-tetradecenylacetate (Z9-14:Ac), an interspecific inhibitor not producedby the females of this species. Vapours of NEM irreversiblyinhibited the electro-antennographic (EAG) responses to Z11-16:Acand Z9-14:Ac. When Zll-16:Ac was applied before and during NEMtreatment, the responses to Z9-14:Ac were preserved and someprotection was observed in the responses to Zll-16:Ac. In return,Z9-14:Ac partially prevented the disappearance of responsesto Zll-16:Ac but not to Z9-14:Ac. A third compound, hexadecylacetate (16:Ac), found in the pheromone gland, but not detectedby the antennal receptors, did not prevent the inhibition causedby NEM.     

Sex pheromone biosynthetic pathway in Spodoptera littoralis and its activation by a neurohormone

Deuterium-labeled fatty acids have been used to elucidate the sex pheromone biosynthetic pathway in Spodoptera littoralis. Label from palmitic acid was incorporated during the scotophase into all the pheromone acetates and their corresponding fatty acyl intermediates. (Z,E)-9,11-tetradecadienyl acetate, the major component of the pheromone blend, is synthesized from palmitic acid via tetradecanoic acid, which, by the action of a specific (E)-11 desaturase and subsequently a (Z)-9 desaturase, is converted into (Z,E)-9,11-tetradecadienoate. By further reduction and acetylation, this compound leads to the dienne acetate. Deuterated precursors applied to the pheromone gland during the photophase were also incorporated into the pheromone. The percentage of labeled (Z,E)-9,11-tetradecadienyl acetate relative to natural compound was significantly higher during the light period. Label incorporation from different intermediates into the pheromone was stimulated by injection of brain-subesophageal ganglion extract during the photophase. The influence of the pheromone biosynthesis-activating neuropeptide on the biosynthetic pathway is discussed.     

Electrophysiological and behavioural evidence for a fourth sex pheromone component in the turnip moth, Agrotis segetum

Abstract. In addition to the pheromone components (Z)-5-decenyl, (Z)-7-dodecenyl and (Z)-9-tetradecenyl acetate (Z5-10:OAc, Z7-12:OAc and Z9-14:OAc), it has previously been shown that the sex pheromone gland of the turnip moth, Agrotis segetum (Lepidoptera: Noctuidae Schiff) contains 10:OAc, 12:OAc, Z5-12:OAc, Z9-12:OAc, 11–12:OAc, Z5-14:OAc, Z7-14:OAc and Z11-16:OAc. To find out whether any of these additional compounds is involved in the sex pheromone communication in A. segetum, a comprehensive electro-physiological and behavioural investigation was conducted. Single-sensillum recordings on male antennae revealed three subtypes of sensilla among the previously so-called Z5-10:OAc sensilla. One subtype was identified having one receptor neurone (A) that responded to Z5-10:OAc with a large spike amplitude and another neurone (B) that responded to (Z)-5-decenol (Z5-10:OH) with a small spike amplitude. In another subtype the B neurone responded to Z5-12:OAc and sometimes also to 27-12:OAc and 10:OAc, in addition to responding to Z5-10:OH. In a third subtype the A neurone responded to all acetates identified from the female pheromone gland, whereas the small spike amplitude neurone was tuned to Z5-10:OH. A flight tunnel assay showed that blends composed of nine, eight or seven compounds were equivalent to the previously identified three-component pheromone blend in eliciting male behavioural responses. In field trapping tests, blends of eleven, nine or seven compounds did, however, catch significantly more moths than the three-component blend. Further assays showed that only 25- 12:OAc could significantly increase the catch numbers when added to the three-component blend, and thus qualified as a fourth pheromone component in A. segerum. The behavioural significance of additional female-produced acetates — for which males possess antennal receptors — is suggested, but may be impossible to confirm because of ‘diminishing returns’ when trying to refine a multicomponent pheromone further.     

Change in reductase activity is responsible for senescent decline in sex pheromone titre in the lightbrown apple moth,Epiphyas postvittana (Walker)

Sex pheromone titre in the tortricid moth Epiphyas postvittana follows a pattern commonly observed in other species of moths: an increase to a peak some time after eclosion (2-3days), and then a slow decline as the female ages. Previous work has shown that this decline is not regulated by the pheromone biosynthesis activating neuropeptide PBAN. Using in vivo and in vitro enzyme assays, and fatty acid methyl ester (FAME) analyses of pheromone precursors in the gland, we have investigated this senescent decline in pheromone titre. The enzyme assays have shown that in older females the fatty acid reductase and fatty acid synthesis enzyme systems decrease in activity (relative to younger females), whereas other enzyme systems involved in pheromone biosynthesis, including limited beta-oxidation (2-carbon chain-shortening), (E)-11-desaturation, and acetylation (by an acetyl transferase) remain unchanged in their activity. Of the two enzymatic processes involved, the more important one contributing to the decline appears to be the fatty acid reductase. This is consistent with FAME analyses of pheromone glands in old and young females, which show little difference in levels of saturated FAME, but a significant increase in the level of the putative precursor, (E)-11-tetradecenoate, of the sex pheromone component (E)-11-tetradecenyl acetate. Thus, this decline in fatty acid reductase activity results in a buildup of the precursor as the female ages. The near ubiquity of fatty acid reductases in moth sex pheromone systems suggests that this may be a common mechanism for the senescent decline of sex pheromone titre in moths.