A study of factors that control biosynthesis of the compounds which comprise the boll weevil pheromone

Biosynthesis of the four monoterpene compounds that comprise the pheromone of the male boll weevil,Anthonomus grandis Boheman, [1, (+)-cis-2-isopropenyl-1-methylcyclobutaneethanol; II, (Z)-3,3-dimethyl-^1,-cyclohexaneethanol; III, (Z)-3,3-dimethyl-^1,-cyclohexaneacetaldehyde; and IV, (E)-3,3-dimethyl-^1,-cyclohexane-acetaldehyde] was studied. More pheromone was biosynthesized in the summer months, somewhat less was produced by males in the presence of females than by isolated males, and the pheromone was concentrated in the gut and surrounding tissue of the abdomen of the males. Incubation of abdomens with the pheromone alcohols yielded related hydrocarbons, aldehydes, and alcohols, which suggested the presence of several enzyme systems. Boll weevils were able to allylically oxidize myrcene and limonene to alcohols, a capability that suggests pheromone precursors may be at least in part inhaled rather than ingested. The hemolymph may then transport the precursor to the gut or some alternative site where allylic oxidation to the pheromone occurs.Coleoptera: Curculionidae.In cooperation with the Mississippi Agricultural and Forestry Experiment Station, Mississippi State, Mississippi 39762. Received for publication.     

Mating behaviour and evidence for a female released courtship pheromone in the signal crayfish Pacifastacus leniusculus

The mating behaviour of the signal crayfish, Pacifastacus leniusculus (Dana), has been categorised into seven distinct stages:; orientation; contact; seizure; turning; mounting; spermatophore deposition; and dismounting. These categories were used in the development of a bioassay to test whether mature females release a sex pheromone during the breeding season to which males respond. Water conditioned by 1) mature females (MF water), 2) immature females (IF water) and 3) freshwater (C water), were injected through standard aquarium air-stones into tanks containing mature males. The behaviour of the male was recorded on video for 15 minutes before and after injection of each test water. The time that the males spent exhibiting the three behavioural categories of quiescent, motile and handling of the air-stone, were recorded. Handling of the air-stone included the mating behaviours of seizure, mounting, and spermatophore deposition onto the surface of the air-stone. Males exposed to MF water exhibited significantly increased levels of motile activity and handling behaviour, than males exposed to C water or IF water. These results demonstrate for the first time the presence of a sex pheromone, released during the breeding season by mature females, that stimulates courtship and mating behaviour in male P. leniusculus.     

Calling behavior and pheromone titer in the smaller tea tortrix moth,Adoxophyes sp. (Lepidoptera: Tortricidae)

The calling behavior and pheromone titer in the female smaller tea tortrix moth,Adoxophyes sp., were investigated under a 1410-hr light-dark photoperiod. Quantitative gas chromatographic analysis of ovipositor extract for (Z)-11-tetradecenyl acetate (Z11–14Ac) and (Z)-9-tetradecenyl acetate (Z9–14Ac), the major pheromone components of this species, obtained on the third day postemergence, indicated that extractable amounts of sex pheromone were present throughout the period of observation. Maximal pheromone titer and calling activity was reached at 8 and 10 hr after onset of scotophase, respectively. The ratio ofZ11–14Ac toZ9–14Ac through the 24-hr period varied significantly. The significance of the sex pheromone component ratio variation on the attraction of males was tested in a field experiment. The ratio of males trapped by the most attractive blend versus the least attractive one was 2.16.     

Temporal patterns of sex pheromone titers and release rates inHolomelina lamae (Lepidoptera: Arctiidae)

Six hydrocarbon components (2-methylhexadecane,n-heptadecane, 2-methylheptadecane, 2-methyloctadecane,n-nonadecane, and 2-methylnonadecane) were identified in sex-pheromone gland extracts and in airborne collections ofHolomelina lamae. Low variability in the ratio of components among individuals indicates tight regulation of blend composition. Minor changes were evident in the quantity and ratio of the blend as a function of time of day. Based on gland extracts, the total quantity of the six components increased from day 1 (X = 6299 ng) to day 4 (X = 7498 ng) and subsequently decreased. No significant correlations were found between total gland contents and wet or dry weights of moths. Emission rates ofH. lamae females were determined from pheromone adsorbed onto Porapak Q. Quantities released peaked shortly after the onset of calling and decreased rapidly as calling continued. Peak release rates ranged from 13 to 350 ng/10 min, and from 37 to 835 ng/60 min. Noncalling females did not emit detectable quantities of pheromone. Based on release rates and the rate of pulsation of the abdominal tip, the average amount released per pulse is not constant. The mean ratio of components released (0.787.45 84.802.842.591.53) was not very different from the ratio of components in gland extracts of 2-day-old females (0.704.1990.12 1.651.911.42). We propose that the blend is atomized rather than volatilized from the gland, thus retaining nearly the same ratios in the female's effluvium as in her gland.     

Heliothis virescens: Response characteristics of receptor neurons in Sensilla Trichodea type 1 and type 2

Partial electroantennograms (EAGs) and single cell recordings fromHeliothis virescens males have demonstrated the presence of pheromones receptor neurons in sensilla trichodea type 2 as well as in type 1. This is supported by cobalt tracing experiments, showing that primary axons from the distal flagellum, containing only s. trichodea type 2, project into the macrogiomerulus complex in the male antennal lobes. Four types of finely tuned pheromone receptor neurons were found in males, whereas in females the corresponding neurons responded mainly to host odors. In males the majority (75 and 18%, respectively) were tuned to the majorHeliothis virescens pheromone components (Z)-11-hexadecenal (Z11-16A1) and (Z)-9-tetradecenal (Z9-14A1). The others (5 and 2%, respectively) responded specifically to (Z)-1 1-hexadecen-1-ol (Z1 1-16OH) and (Z)-1 1-hexadecen-1-ol acetate (Z1 1-16Ac). No neurons responding selectively to the minor pheromone components were found. The Z11-16A1 neurons of both sensilla types possessed similar specificity. However, the sensitivity decreased toward the medial and distal part of the flagellum, where s. trichodea type 2 are located. This suggests that the pheromone concentrations can be detected peripherally by a spatial as well as a temporal mechanism. Differences in temporal response patterns (pronounced phasic vs. tonic component) were found within the same type of neurons, suggesting different ability to encode intermittency of the pheromone plume as well as to mediate maintenance of flight.     

Genetic aspects of interpopulational differences in pheromone blend of cabbage looper moth,Trichoplusia ni

The genetic basis of interpopulational differences in the pheromone blend emitted by the cabbage looper moth,Trichoplusia ni (Hübner), was examined by crossing individuals from a field-derived population (P₁) with individuals from a long-maintained laboratory colony (P₂). These colonies differed in the emission rate and relative proportions of four of the five known minor pheromone components, but not in the emission rate of the major component, (Z)-7-dodecenyl acetate (Z7-12Ac). These differences in pheromone blend were quantitatively small but biologically significant, because in the field, males responded preferentially to traps baited with a pheromone blend that is similar to that emitted by P₁ females relative to a blend similar to that emitted by P₂ females. In initial crosses, variation in the quantity and quality of pheromone blends among families of P₁, P₂, and F₁ hybrid females was examined. In F₁ females the relative proportions (quantity relative to the major component) of (Z)-5-dodecenyl acetate (Z5-12Ac) and (Z)-7-tetradecenyl acetate (Z7-14Ac) were intermediate to parental lines. In a second more extensive set of crosses, analyses included P₁, P₂, F₁, F₂, and selected backcrosses. The relative proportion of Z5-12Ac, Z7-14Ac, and Z9-14Ac emitted by F₁ females were intermediate to parental lines. The frequency distributions of relative proportions of these components emitted by females were not consistent with those expected under a single autosomal or sex-linked gene hypothesis, suggesting that more than one gene is involved in the quantitative differences in the pheromone blend.     

Orientation of boll weevil,Anthonomus grandis boh. (Coleoptera: Curculionidae), to pheromone and volatile host compound in the laboratory

Behavioral responses of male and female boll weevils to the aggregation pheromone, grandlure, and the major volatile of cotton, -bisabolol, were investigated using a new dual-choice olfactometer. Dosage-response experiments revealed both males and females to be attracted by the aggregation pheromone at the 1.0 g dosage. However, only males were attracted to -bisabolol (1.0 g). Both sexes were repelled by the highest dosage of-bisabolol tested (10 g). In preference experiment, males chose grandlure over -bisabolol, while both sexes chose the combination of grandlure + -bisabolol over -bisabolol alone. There was some evidence for synergism between pheromone and plant odor for the females. The results correlate well with previous electrophysiological and behavioral experiments.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Alpha-acaridial a female sex pheromone from an alarm pheromone emilting mite Rhizoglyphus robini

The female sex pheromone of Rhizoglyphus robini Claparède (Astigmata: Acaridae) was identified as -acaridial [2(E)-(4-methyl-3-pentenyl)- butenedial], which stimulated males sexually and enhanced the frequency of male mounting behavior. Although a hexane extract of females manifested alarm pheromone activity against tested males due to the presence of the alarm pheromone neryl formate, silica gel column fractions containing -acaridial evoked increased mounting behavior by males at a dose of 0.1 female equivalent. Synthetic -acaridial at a dose of 10 ng showed a peak of activity as a sex pheromone, with a convex dose–response relationship. Its content was determined to be 388 ± 244 ng per female and 163 ± 97 ng per male by GC. This is the first time that two pheromones (the alarm pheromone neryl formate, and the sex pheromone -acaridial) have been demonstrated to be components of the same opisthonotal gland secretion in astigmatid mites. A mechanism for the appropriate expression of the two pheromones by the mites under different conditions is proposed.     

Spruce budworm (Choristoneura fumiferana) pheromone chemistry and behavioral responses to pheromone components and analogs

This paper reviews the sex pheromone chemistry and pheromone-mediated behavior of the spruce budworm and related coniferophagous (Choristoneura) budworms. InC. fumiferana, temporal changes in pheromone-gland monounsaturated fatty acids (pheromone precursors) enable the prediction of the primary sex pheromone components. This technique may also be applicable for predicting additional pheromone components. Tetradecanal (14 Ald), previously shown to enhance close-range precopulatory behavior, lowers the threshold of response by males for upwind flight to a pheromone-component source. Spruce budworm males maintain upwind flight to 955 (E/Z)-1,12-pentadecadiene (diolefin analog) after initiating upwind flight to a primary-component pheromone source (955E/Z11-14Ald). This is the first demonstration of apparently normal male flight responses to a pheromone analog.Lepidoptera: Tortricidae     

Response of male potato stem borer moths,Hydraecia micacea (Esper) to conspecific females and synthetic pheromone blends in the laboratory and field

Behavior of males ofHydraecia micacea (Esper) responding to virgin females and to synthetic pheromone blends were investigated in a laboratory wind tunnel. The synthetic blend consisted of saturated 14Ac (68.9%),Z9–14Ac (3.4%),E11–14Ac (14.6%), andZ11–14Ac (13.1%). Virgin females were significantly better lures than the four-component synthetic blend for most behaviors. By deleting components individually from the four-component blend,Z9–14Ac,Z11–14Ac, and saturated 14Ac were found to be necessary for communication butE11–14Ac was found to have no effect on typical pheromone-mediated reproductive behaviors. Close-range studies suggested that chemicals of low volatility, released from moths, were important in eliciting copulation attempts. Field studies reinforced laboratory findings regarding the effectiveness of different lures and indicated thatHeliothis traps were the most effective for monitoring.     

Sex pheromone evidence for two distinct taxa withinGraphania mutans (Walker)

The sex pheromones of two populations ofGraphania mutans (Walker) were analyzed. Females from an Auckland population produced (Z)-9-tetradecenol (Z9-14OH), (Z)-9-tetradecenyl acetate (Z9-14OAc), (Z)-7-tetradecenol (Z7-14OH) and (Z)-7-tetradecenyl acetate (Z7-14OAc), while females from a Lincoln population produced these four compounds and a large amount of (Z)-9-tetradecenal (Z9-14Ald). Significant differences, paralleling the difference between females, were observed when the responses of males of both populations to the above and other related compounds were tested by electroantennogram, field-trapping, and wind-tunnel bioassays. The most distinct difference was observed in the wind tunnel. Males from both taxa flew upwind and touched pheromone sources containing sex pheromone extract of females of their own taxon, but either did not initiate upwind flight or arrested upwind flight shortly after taking flight in response to extract from females of the other taxon. The difference between the pheromone systems of the two populations is probably due to the presence and importance of Z9-14Ald in the pheromone blend of the Lincoln population. Thus the addition of a relatively large amount of Z9-14Aid to a four-component pheromone blend (i.e., Z9-14OH, Z9-14OAc, Z7-14OH, andZ7-14OAc) attractive to Auckland males completely suppressed trap catches of male G.Mutans in Auckland but large numbers of males were caught at both Lincoln and Nelson in traps baited with this five-component blend. In wind-tunnel studies, the addition of even small (1% of amount of Z9-14OH) amounts ofZ9-14Ald to the four-component blend resulted in a significantly greater proportion of Auckland males arresting upwind flight than to the four-com ponent blend. It is suggested that these two populations of G. nations represent distinct sibling species within the described concept.LepidopteraNoctuidaeHadeninae.     

Behavioral responses of maleArgyrotaenia velutinana (Lepidoptera: Tortricidae) to components of its sex pheromone

Males of the redbanded leafroller,Argyrotaenia velutinana (Walker) (Lepidoptera: Tortricidae), were studied for their behavioral responses in laboratory olfactometers and in the field to the 3 components of the female-produced sex pheromone:cis-11-tetradecenyl acetate (c11–14Ac),trans-11-tetradecenyl acetate (t11–14Ac), and dodecyl acetate (12Ac). Dodecyl acetate, when evaporated with c11–14Ac (8%trans) in the field, modified the behavior of feral males nearby the chemical source, causing an increase in the frequency of landing and close approach to the pheromone dispenser. Apparently, an inflight behavioral modification concerning landing or not landing occurs within 60 cm of the source and is mediated by 12Ac. In laboratory olfactometers, c11–14Ac (8%trans) demonstrated a lower threshold for male activation than pure c11- and t11–14Ac and blends of the two isomers. Additionally, over a wide range of dosages, males responded with optimum wing-fanning response to c11–14Ac (8%trans) compared to pure c11–14Ac, c11–14:Ac (30%trans), and pure t11–14Ac, suggesting that thecistrans ratio rather than absolute amounts of either isomer, is a crucial factor in eliciting male response. When presented with c11–14Ac (8%trans) (11), dodecyl acetate caused a significant prolongation of wing-fanning over c11–14Ac (8%trans) alone and resulted in a greater percentage of males moving upwind to the source. Since the increase in wing-fanning and orientation occurred at higher concentrations of the 3-component mixture, the effect of 12Ac in the laboratory may reflect the close-range role of 12Ac in the field.     

Influence of (Z)-11-hexadecen-1-ol on field performance ofHeliothis virescens pheromone in a PVC dispenser as evidenced by trap capture

Field studies were conducted to determine the effect of (Z)-11-hexadecen-1-ol (Z11-16 OH) on capture of tobacco budworm (TBW),Heliothis virescens (F.), males when added to two-component (HV-2) and six-component (HV-6) pheromone blends dispensed from a polyvinyl chloride (PVC) substrate. Numbers of males caught in traps baited with PVC dispensers containing 0.25% Z11-16 OH, relative to total pheromone content, were significantly higher than numbers caught with dispensers containing noZ11-16 OH. Catches of TBW were also increased significantly in some tests whenZ11-16 OH was formulated in the bait at a 1% concentration. Catches were significantly reduced with dispensers containing 5.95%Z11-16 OH compared with those containing noZ11-16 OH. There were no differences in catch between traps baited with HV-2 vs. HV-6 or HV-2 + 0.25%Z11-16 OH vs. HV-6 + 0.25%Z11-16 OH when formulated in PVC substrate.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Sex pheromone components of the blueberry leaftier mothCroesia curvalana kearfott (Lepidoptera: Tortricidae)

The GC-MS and GC-EAD analyses of sex-gland components and sex-gland-released volatiles have identified (E)- and (Z)-11-tetradecenal (9010) and (E)- and (Z)-11-tetradecenyl acetate (8515) as components of the sex pheromone chemical communication system ofCroesia curvalana (Kearfott). The aldehyde-to-acetate ratio of 91 was found in the gland-released components. This blend at a 0.1–1 g/day release rate from PVC lures was shown to be as effective as virgin females in the trapping of maleC. curvalana.     

Identification of sex pheromone of calendula plume mothPlatyptilia williamsii

The sex pheromone of the calendula plume moth,Platyptilia williamsii was identified as (Z)-11-hexadecenal (Z11–16Aid). Extracts of female sex pheromone glands contained several compounds when analyzed by capillary and packed-column GLC. However, airborne collections of volatiles from glands contained only one of these compounds, having the same retention time asZ11–16Ald. GC-MS and microozonolysis analyses of the natural product were consistent with those of syntheticZ11–16Ald. In a flight tunnel, males oriented upwind and touched sources ofZ11–16Ald and gland extract with equal frequency. Field tests of syntheticZ11–16Ald already have shown it to be a potent sex attractant for males of this species. This study further supports the hypothesis thatP. williamsii and a sympatric species,Platyptilia carduidactyla, are not reproductively isolated by chemical differences in the composition of the sex pheromone, but rather by temporal differences in sexual activities.     

Effect of formulations and dispensers on attractiveness of virelure to the tobacco budworm

Formulations of virelure, the synthetic sex pheromone of the tobacco budworm,Heliothis virescens (F.), were developed, bioassayed in traps in field cages, and used in traps to survey populations in plant hosts. Virelure (10 mg) laminated between thin sheets of vinyl polymer plastic was attractive to male moths for 21 days, and attractiveness did not regress appreciably for the first 7 days. Another dispenser was an 8 × 30-mm cigarette filter encased in a glass shell vial. A mixture of 10 l (Z)-11-hexadecenal and 0.5 l (Z)-9-tetradecenal, the pheromone components, formulated with wheat germ oil andd-alpha tocopherol (91) in 0.5 ml CH₂Cl₂ (WGOE) was still attractive to males after 5 days. Cottonseed oil, polyethylene glycol 600 distearate (peg-600-d), and peg-6000-d also inhibited excessive vaporization and oxidation of virelure. Virelure (21.25 l) formulated on filters with WGOE and used as bait (replaced weekly) in survey traps caught 27,263 males in 1975; analysis of catches each day for 7-day periods showed that most males were caught within 3 days after baiting, and attractiveness regressed considerably during the last 3–4 days of each week. Four ratios of virelure components were tested as bait (20 mg) in saucer-type pheromone traps, and the 161 ratio caught significantly more male moths than ratios of 241, 321, or 401.Lepidoptera Noctuidae.In cooperation with the Texas Agricultural Experiment Station, Texas A & M University, College Station 77843.This paper reports the results of research only. Mention of a pesticide in this paper does not constitute a recommendation for use by the USDA nor does it imply registration under FIFRA as amended. Also, mention of a commercial or a proprietary product in this paper does not constitute an endorsement by the USDA.     

Sex pheromone of the false codling mothCryptophlebia leucotreta (Lepidoptera:Tortricidae)

The sex pheromone ofCryptophlebia leucotreta females is a mixture of (E)-8- and (Z)-8-dodecenyl acetate (dda). The compounds have been isolated from extracts ofC. leucotreta females and were identified by means of chromatography on a silver-impregnated column, and by combined GC-MS analysis and ozonolysis. Optimal catches of males were obtained with mixtures of (E)-8- and (Z)-8-dda in the range of 7030 to 3070.     

Redundancy in a chemical signal: Behavioral responses of maleTrichoplusia ni to a 6-Component sex pheromone blend

The flight response of maleTrichoplusia ni was observed in a flight tunnel to a sex pheromone blend composed of six components:Z7–12Ac, 12Ac,Z5-12Ac, 11-12Ac,Z7-14Ac, and Z9-14Ac. The number of males reaching a 3000-g source of this blend was > 95%, equal to that observed to female glands and significantly greater than with the previously identified two-component blend (Z7-12Ac + 12Ac). In subtraction tests, all five-component blends, with the exception of the blend lacking the primary componentZ7-12Ac, and several four-component blends elicited similar peak levels of upwind flight, source contacts, and hairpencil displays to that observed with the six-component blend. We characterize the substitution of certain minor components for one another as a form of redundancy in the chemical signal and suggest that it contributes to response specificity and signal recognition in males. The results also support the concept that the full blend of components acts as a unit to influence male behavior at all phases of the response. Individual minor components were not responsible for eliciting specific behaviors in the sequence.     

Identification of sex pheromone components of jack pine budworm,Choristoneura pinus pinus freeman

Chemical identification and field-trapping experiments have shown that a blend of 8515 (E,Z)-11-tetradecenyl acetates and 8515 (E,Z)-11-tetradecen-1-ols (in a 91 ratio) are female sex pheromone components for jack pine budworm,Choristoneura pinus pinus. This blend of chemicals, formulated in PVC (0.1 %, w/w) sources is as effective a trap bait as virgin females. Preliminary wind tunnel observations have indicated that this blend, effective as a trap bait, is not equivalent to females.Lepidoptera: Tortricidae.     

Behavioral and neurosensory responses of the boll weevil,Anthonomus grandis Boh. (Coleoptera: Curculionidae), to fluorinated analogs of aldehyde components of its pheromone

Competitive field tests with -fluorinated analogs of compounds III and IV (III--F and IV--F, respectively) of the boll weevil,Anthonomus grandis Boh., aggregation pheromone showed these compounds, when combined with the other pheromone components [(±)-I and II], to be as attractive as grandlure [(+)-I, II, and III+IV]. Dose-response curves constructed from electroantennograms of male boll weevils to serial stimulus loads of III, IV, III--F, IV--F, and the corresponding acyl fluorinated analogs (III-acyl-F and IV-acyl-F) showed the -fiuorinated analogs to be as active as the pheromone components (threshold=0.1 g), while the acyl fluorinated analogs had a 10-100 x higher threshold (=1-10 g). Single-neuron recordings showed that IV neurons and II neurons (Dickens, 1990) responded to IV--F and III--F, respectively, while IV-acyl-F and III-acyl-F were inactive. Since a previous study showed compounds I, II, and IV to be essential for behavioral responses in the field, it seems likely that the activity of the -fluorinated analogs observed here is due to the stimulation of IV neurons by IV--F as indicated in single neuron recordings.