Olfactory reception of potential pheromones and plant odors by tarnished plant bug,Lygus lineolaris (Hemiptera: Miridae)

Olfactory reception of potential pheromones and host-plant odors by male and female tarnished plant bugs (TPBs),Lygus lineolaris (Hemiptera: Miridae), was investigated by utilizing electroantennogram (EAG) techniques. In general, EAGs were similar between the sexes. Among 31 compounds of seven chemical groups tested, insect-produced butyrates and host-plant-containing green leaf volatiles (GLVs) were the most active. Hexyl butyrate and (E)-2-hexenyl butyrate elicited greater EAGs in males than in females. Females responded with significantly greater EAGs to alcohol and aldehyde GLVs than to their acetate derivatives. Among GLVs, sexual dimorphism was also observed in response to (E)-2-hexenol and (E)-2-hexenal. Females were more sensitive to the monoterpene geraniol than were males. While nonanal was the most stimulatory compound tested, no sexual differences in EAGs to this compound were observed. These studies reveal olfactory receptors on TPB antennae responsive to insect and host-plant volatiles that are likely to play a role in host finding and sexual attraction.     

Electroantennographic and behavioral responses of the sphinx moth Manduca sexta to host plant headspace volatiles

Coupled gas chromatography with electroantennographic detection (GC-EAD) using antennae of adult female Manduca sexta was employed to screen for olfactory stimulants present in headspace collections from four species of larval host plants belonging to two families: Solanaceae—Lycopersicon esculentum (tomato), Capiscum annuum (bell pepper), and Datura wrightii; and Martyniaceae—Proboscidea parviflora. Headspace volatiles were collected from undamaged foliage of potted, living plants. GC–EAD revealed 23 EAD-active compounds, of which 15 were identified by GC-mass spectrometry. Identified compounds included aliphatic, aromatic, and terpenoid compounds bearing a range of functional groups. Nine EAD-active compounds were common to all four host plant species: (Z)-3-hexenyl acetate, nonanal, decanal, phenylacetaldehyde, methyl salicylate, benzyl alcohol, geranyl acetone, (E)-nerolidol, and one unidentified compound. Behavioral responses of female moths to an eight-component synthetic blend of selected tomato headspace volatiles were tested in a laboratory wind tunnel. Females were attracted to the blend. A comparison of responses from antennae of males and females to bell pepper headspace volatiles revealed that males responded to the same suite of volatiles as females, except for (Z)-3-hexenyl benzoate. EAD responses of males also were lower for (Z)- and (E)-nerolidol and one unidentified compound. Electroantennogram EAG dose–response curves for the 15 identified EAD-active volatiles were recorded. At the higher test doses (10–100 g), female antennae yielded larger EAG responses to terpenoids and to aliphatic and aromatic esters. Male antennae did respond to the higher doses of (Z)-3-hexenyl benzoate, indicating that they can detect this compound. On the basis of ubiquity of the EAD-active volatiles identified to date in host plant headspace collections, we suggest that M. sexta uses a suite of volatiles to locate and identify appropriate host plants.     

Responses of the Mediterranean Pine Shoot Beetle Tomicus destruens (Wollaston) to Pine Shoot and Bark Volatiles

The pine shoot beetle Tomicus destruens has two dispersal phases per generation. In the first, mature adults move toward trunks of dying pines to lay eggs; in the second, callow adults move toward the shoots of healthy pines for maturation feeding. However, there is no information on the chemical stimuli that govern host selection by T. destruens adults. The aims of this study were: (1) to identify the volatiles released by shoots and bark of stone pine that are behaviorally and electrophysiologically active on T. destruens; (2) to verify which blends and concentrations of such volatiles are differently active on males and females, as well as on callow and mature adults, during the two host search phases (breeding and feeding). A four-arm olfactometer was used to test the behavior of walking T. destruens adults toward various sources of volatiles including fresh shoots and bark, their collected volatiles, and two synthetic blends. For each odor, the behavior of both callow and mature males and females was recorded individually. Shoot and bark extracts were analyzed by coupled gas chromatography and mass spectrometry (GC-MS), and tested by gas chromatography coupled with electroantennography (GC-EAD) on T. destruens males and females. Two blends of two (alpha-pinene and beta-myrcene; blend A) and three (alpha-pinene, beta- myrcene, and alpha-terpinolene; blend B) synthetic compounds, chosen among those that induce EAD responses and known to be attractive for other bark beetle species, were tested in the olfactometer at five concentrations. Insect behavior was affected by the degree of sexual maturation but not by sex. Callow insects were attracted by shoots and their extracts, while mature individuals by bark and its extracts. Six extracted compounds were active on T. destruens antennae: limonene, (Z)-3-hexen-1-ol and beta-caryophyllene, alpha-pinene, beta-myrcene, and alpha-terpinolene. alpha-Terpinolene, released only by bark, was active only on mature insects, whereas (Z)-3-hexen-1-ol, released only by shoots, was active only on callows. Males and females showed similar EAD responses. Of the six extracted volatiles, two were attractive for callow adults (blend A) and three for matures (blend B). In both cases, responses were positively correlated with blend concentration, although a repellent effect was noted at the highest concentrations.     

Sex-Related Perception of Insect and Plant Volatiles in Lygocoris pabulinus

We recorded electroantennograms of male and female Lygocoris pabulinus antennae to 63 insect and plant volatiles. EAGs were between 100 and 500 V. Overall, male EAGs were about twice the size of female EAGs. In both sexes, largest EAGs were recorded to (E)-2-hexenyl butanoate and (E)-2-hexen-1-ol. Response profiles were similar in both sexes. However, male antennae were more sensitive to a number of esters, especially the butanoates and pentanoates. Female antennae were more sensitive to nine of the 19 plant volatiles, i.e., to hexan-1-ol, heptan-1-ol, 1-octen-3-ol, 2-heptanone, (R)-carvone, linalool, geraniol, nerol, and methyl salicylate. Sexual differences in responses suggest that males are more sensitive to insect-produced pheromone-type compounds, whereas females are more sensitive to plant compounds for their orientation towards oviposition sites.     

Female-Biased Attraction of Oriental Fruit Fly, Bactrocera dorsalis (Hendel), to a Blend of Host Fruit Volatiles From Terminalia catappa L.

Coupled gas chromatography-electroantennogram detection (GC-EAD) analysis of volatiles from tropical almond fruit, Terminalia catappa L., revealed 22 compounds that were detected by antennae of oriental fruit fly females, Bactrocera dorsalis (Hendel). Both solid-phase microextraction (SPME) and Porapak Q were used for sampling odors in fruit headspace, with SPME collections producing larger EAD responses from a greater number of compounds. Geranyl acetate and methyl eugenol elicited the largest EAD responses. A synthetic blend containing SPME collected, EAD stimulatory compounds showed female-biased attraction in laboratory wind tunnel bioassays, but heavily male-biased trap captures in a larger olfactometer arena. A nine-component subset of compounds eliciting relatively small EAD responses (EAD minor) and consisting of equal parts ethanol, ethyl acetate, ethyl hexanoate, hexyl acetate, linalyl acetate, ethyl nonanate, nonyl acetate, ethyl cinnamate, and (E)-β-farnesene, attracted mainly females. This EAD minor blend was as attractive to females and much less attractive to males when compared to torula yeast in field cage experiments using glass McPhail traps. Similar results were obtained with outdoor rotating olfactometer tests in which the EAD minor blend was almost completely inactive for males.     

Communication ecology of webbing clothes moth: 2. Identification of semiochemicals mediating attraction of adults to larval habitat

Our objective was to identify the semiochemicals that mediate attraction of the webbing clothes moth (WCM), Tineola bisselliella (Lepidoptera: Tineidae), to suitable larval habitat. Coupled gas chromatographic-electroantennographic detection (GC-EAD) analyses of Porapak Q-captured bioactive volatiles from horseshoe crab, and dried but untanned vertebrate pelts revealed numerous EAD-active volatiles. These volatiles were identified by comparative GC-mass spectrometry and GC-EAD analyses of natural and synthetic compounds. A blend of 28 synthetic candidate semiochemicals attracted both male and female WCM. Experiments deleting various components determined that saturated aldehydes—but not unsaturated aldehydes, saturated hydrocarbons, saturated alcohols, or ketones—were essential for blend attractiveness. A blend of nonanal, the single most attractive aldehyde, in combination with geranylacetone was more attractive to WCM than the 28-component blend or dried, untanned animal pelt. Selection of larval habitat resides more with male than female WCM, as indicated by stronger EAD responses from male than female antennae to habitat-derived semiochemicals, and more selective and early response to habitat cues by males than females. Exploitation of nonanal and geranylacetone as resource-derived semiochemicals by both adult WCM and its larval parasitoid, Apanteles carpatus, is an example of convergent semiochemical parsimony.     

Scented Males and Choosy Females: Does Male Odor Influence Female Mate Choice in the Mediterranean Fruit Fly?

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), displays a lek mating system characterized by a high level of female discrimination among potential mates. The basis of female choice is not understood, but recent studies indicate that male exposure to the aroma of certain plant structures or essential oils may increase mating success. In particular, exposure to the aroma of ginger root oil (GRO) enhances male mating frequency, and several sterile-male release programs against C. capitata have incorporated ‘aromatherapy’ (large-scale exposure of pre-release insects to GRO) to increase the effectiveness of control efforts. We investigated the mechanism underlying female preference for GRO-exposed males. Two sets of experiments were conducted. In the first, we monitored female attraction to (1) freshly killed flies, or (2) paper discs that contained hexane extracts from varying treatments. In these tests, females were sighted more often (1) near GRO-exposed than non-exposed males (even when the males were visually concealed) and (2) near extracts from GRO-exposed than non-exposed males. These findings suggest a ‘perfume effect’, whereby female mate choice is mediated by olfactory differences. In the second set, we compared (1) mate choice between intact females and females from which both antennae had been surgically removed, and (2) mating success between intact males and males from which both antennae had been surgically removed before GRO exposure. Intact females preferred GRO-exposed males, whereas females lacking both antennae rarely mated and showed no preference between GRO-exposed and non-exposed males. In the opposite treatment (intact females but surgically altered males), GRO-exposed males lacking both antennae mated as frequently as GRO-exposed intact males. These data suggest that female choice was dependent on olfactory perception of male odor but that male mating success did not depend on olfactory perception of GRO aroma, suggesting, in turn, that GRO conferred a mating advantage through an external phenomenon (possibly alteration of cuticular scent) rather than through internal processing (pheromone synthesis).     

Electrophysiological and Behavioral Responses of the Cabbage Moth to Plant Volatiles

Plant volatiles from cabbage and chrysanthemum were studied as to how they affect behavior of the cabbage moth, Mamestra brassicae (L.). Chemical, electrophysiological, and behavioral techniques were used. The electroantennographic (EAG) evaluation of selected compounds from Brassi-caceae showed that isothiocyanates (NCS) elicited weak responses, and some did not evoke significant EAG responses at all. Green leaf volatiles (GLVs) evoked the strongest responses in both male and female antennae. The capacity of NCS to stimulate upwind flight of mated females was not different at doses of 10^–7, 10^–6, or 10^–5 g when tested in a wind tunnel. At the higher doses, allyl NCS stimulated upwind flight in the females more than the other compounds. Allyl NCS was significantly better than the other compounds at stimulating females to land on targets. Mated females flew upwind and landed on the targets with allyl NCS more often than virgin females and males. With respect to the behavioral activity of GLVs, only (E)-2-hexenal and (Z)-3-hexenyl acetate elicited upwind flight and landing in females. Ten compounds were identified from a chrysanthemum extract by using coupled gas chromatography–electroantennography. Five of these, (Z)-3-hexenyl acetate, 1-8-cineole, -terpinene, chrysanthenone, and camphor, elicited upwind flight of mated females, but only three stimulated landing.     

Mechanism of aggregation behavior inMaladera matrida Argaman (Coleoptera: Scarabaeidae)

AdultMaladera matrida Argaman (Coleoptera: Scarabaeidae: Melolonthinae) males emerge from soil for an active period at dusk, a few minutes before the females. Adults are found during most of the active hours on the foliage in aggregations composed of an equal sex ratio. The mechanism of aggregation behavior ofM. matrida beetles was studied in a Y-shaped olfactometer. No evidence was found for the existence of an aggregation pheromone released either by males or by females, but behavior tests indicate that adultM. matrida beetles, males as well as females, are attracted to volatiles of an injured host plant. The following scenario is suggested: Males emerge daily from soil at dusk, a few minutes before the females, and immediately start feeding. Additional males are attracted to the injured host's volatiles and form aggregations. When females emerge from soil, the attractant volatiles are concentrated in spots, and the females join the aggregations, forming an equal sex ratio.     

(R)-acetoin-female sex pheromone of the summer chafer Amphimallon solstitiale (L.)

Extracts of Amphimallon solstitiale (L.), a well known, widely distributed and rather common European scarab beetle, were analyzed by GC-MS and GC-EAD. Acetoin -(R):(S) < 9:1 - as well as 2,3-butanediol -(2R,3R):(2S,3S) :meso = 1:1:9 - were present in extracts of both males and females. Although (2S,3S)-butanediol did not show any EAD activity, the other compounds elicited strong responses exclusively with male antennae. In contrast, several EAD active green leaf volatiles were detected equally well by male and female antennae. During preliminary field bioassays, (R)-acetoin was highly attractive to swarming males, whereas neither rac-acetoin nor the 2,3-butanediols showed activity. Therefore, (R)-acetoin is the female sex pheromone of A. solstitiale.     

Evidence for volatile male-produced pheromone in banana weevilCosmopolites sordidus

Females of the banana weevil,Cosmopolites sordidus, were attracted to and made longer visits to live conspecific males, trapped volatiles from males, and dissected male hindguts in a still-air olfactometer. Male weevils were attracted to volatiles trapped from males and made longer visits to live males and volatiles from males. Live females, collected volatiles from females and female hindguts, elicited small or no behavioral responses from either sex. Electroantennogram (EAG) responses from both male and female antennae were elicited by collected volatiles from males and by dichloromethane extracts of male hindguts and bodies but not by surface washes of males. No significant EAG responses were given to equivalent material from females. It is therefore suggested that male banana weevils release an aggregation pheromone via their hindgut.     

Laboratory and field evidence for maleproduced aggregation pheromone inRhynchophorus cruentatus (F.) (Coleoptera: Curculionidae)

Laboratory and field assays were conducted to determine if palmetto weevil,Rhynchophorus cruentatus (F.), adults produce an aggregation pheromone. Attraction of females in a Y-tube olfactometer to conspecific males was greater than to clean air. Male and female attraction to conspecific male volatiles combined with host-palm,Sabal palmetto (Walter), volatiles was greater than to host-palm volatiles alone. Similarly, more weevils were caught in the field in traps baited with conspecific males plus host-palm tissue than in similar traps baited with only males, or palm tissue, or females, or females plus palm tissue. These results suggest thatR. cruentatus males produce an aggregation pheromone(s) that is highly attractive to conspecific adults of both sexes when combined with host-palm volatiles. This study is an important step towards understanding the chemical ecology ofR. cruentatus.     

Olfactory responses ofIps plastographus maritimus lanier (coleoptera: Scolytidae) to insect and host-associated volatiles in the laboratory

Attraction of both sexes ofIps plastographus maritimus Lanier to bark-phloem-xylem discs of Monterey pine,Pinus radiata D. Don, was demonstrated in the laboratory. Increasing concentrations of male and female volatiles trapped separately and released in a one-to-one ratio decreased attraction for both sexes combined. Attraction of both sexes to volatiles derived from males and females tunneling together in a one-to-one ratio increased with increasing concentration of extract. Attraction of males and females to male-infested discs and to trapped male volatiles increased with increasing dose of males or male extract. Attraction of males and females to female-infested discs and to trapped female volatiles was also demonstrated. The presence of females in male galleries reduced the attractiveness of infested disks to both sexes combined. Increasing numbers of females, tunneling separately from males in the same disc, reduced attraction of males, but not females. When a constant attractive dose of male volatiles was released with increasing doses of female volatiles, there was no difference in response of either sex when female volatiles were present compared with the response to male volatiles alone. When a constant attractive dose of male volatiles was released with increasing concentrations of volatiles derived from males and females tunneling together in a one-to-one ratio, attraction ofI. p. maritimus decreased. Response of females was frequently higher than that of males to the same attractant source. Hence, both sexes produce an attractant, and both sexes tunneling together in the same gallery reduce attraction of males and females to an attractive dose of male attractant.     

Analysis of the Volatiles Emitted by Whole Flowers and Isolated Flower Organs of the Carob Tree Using HS-SPME-GC/MS

The volatiles emitted by fresh whole flowers and isolated flower organs of male, female, and hermaphrodite carob trees (Ceratonia siliqua L.; Leguminosae) were analyzed by headspace solid-phase microextraction followed by capillary gas chromatography and mass spectrometry. The headspace of carob flowers is mainly constituted of high amounts of monoterpenes and sesquiterpenes, and more than 25 compounds were identified. The gender and cultivar affected both the qualitative profile and the relative abundances of the volatiles of whole flowers and isolated floral organs. Linalool and its derivatives (cis-linalool furan oxide, 2,2,6-trimethyl-3-keto-6-vinyltetrahydropyran, cis-linalool pyran oxide, and trans-linalool furan oxide), α-pinene, and α-farnesene were the dominant volatiles. Female flowers had a higher diversity of volatile compounds than males and hermaphrodites, but a lower abundance of the major ones. Similarly, the floral scent of female flowers of cv. Mulata had a higher content of volatiles but a lower abundance of the major ones, when compared to cv. Galhosa. In each of the three gender types of flowers, the nectary disks seemed to be the major source of volatiles.     

Olfactory receptor cell responses ofIps grandicollis (eichhoff) (Coleoptera: Scolytidae) to intra- and interspecific behavioral chemicals

Electrophysiological recordings from antennal olfactory receptor cells were obtained fromIps grandicollis. Recordings were made from olfactory receptor cells from nine regions of the antennae in response to stimulation with the semiochemicals-pinene, frontalin,endo-brevicomin, verbenone,trans-verbenol,cis-verbenol, ipsdienol, and ipsenol. In many cases, up to two cells were recorded concurrently from the same location. When compared to males, females had a greater percentage of cells responsive to the primary pheromones ofDendroctonus frontalis, frontalin andtrans-verbenol, and ofIps spp., ipsdienol and ipsenol. Among females, more cells responded totrans-verbenol and theIps-produced volatiles than to host or otherD. frontalis-produced compounds. Olfactory cells of males responded mostly tocis-verbenol, followed by-pinene, verbenone,trans-verbenol, andendo-brevicomin. Of those cells responsive primarily to one compound, the greatest percentage were responsive totrans-verbenol in females and to verbenone in males. The response of the antennal olfactory receptor cells to semiochemicals used by male and femaleI. grandicollis is consistent with the presence of these compounds during the host colonization period for each sex. Our results, which show a lack of specificity in most pheromone and host odor receptor cells, is in contrast with previously published accounts of olfactory receptor cell specificity in otherIps species.     

Electrophysiological and Behavioral Responses of the Black-Banded Oak Borer, <Emphasis Type="BoldItalic">Coroebus florentinus</Emphasis>, to Conspecific and Host-Plant Volatiles

Aspects of the chemical ecology of the black-banded oak borer, (BBOB) Coroebus florentinus (Coleoptera: Buprestidae), were studied. Odors produced by males and females were similar, both qualitatively and quantitatively. Nonanal, decanal, and geranylacetone, identified in the headspace of both sexes, elicited strong electroantennographic responses from male antennae, but not from female antennae. In dual-choice olfactometer experiments, a blend of these three compounds was attractive to both sexes; males responded to decanal alone, while females responded to geranylacetone alone, suggesting that these compounds are responsible for activity of the blend to the respective sexes. Antennae of both sexes responded electroantennographically to the green leaf volatiles (E)-2-hexenal, (E)-2-hexenol, 1-hexanol, (Z)-3-hexenyl acetate, and n-hexyl acetate, all identified from the host plant Quercus suber. In behavioral experiments, only females were attracted to host-plant odors, and in tests with synthetic compounds, females were attracted to (E)-2-hexenol, 1-hexanol, and (Z)-3-hexenyl acetate. It is likely that these compounds play a role in foraging and/or oviposition behavior of BBOB females.     

Identification of the female-produced sex pheromone of the scarab beetle,Hoplia equina

Hoplia equina LeConte (Coleoptera: Scarabaeidae: Melolonthinae) is a beetle pest of cranberry beds in Massachusetts. Larvae feed on the roots of the cranberry plant, reducing yield as well as vine density. The female sex pheromone was identified as 2-tetradecanone. There were eight compounds found in the airborne volatiles collected from females that elicited antennal responses from males. Of the eight compounds tested (nonanal, decanal, dodecanal, 2-dodecanone, 2-tridecanone, 2-tetradecanone, 2-pentadecanone, and 2-hexadecanone), 2-tetradecanone was the only one that attracted male beetles in the field. Combining any of the other seven antennally active compounds with 2-tetradecanone did not increase male capture.     

Evidence for volatile chemical attractants in the beetleMaladera matrida argaman (Coleoptera: Scarabaeidae)

TheMaladera matrida beetle (Coleoptera, Scarabaeidae, Melolonthinae), a relatively new species to science, was first identified in Israel in 1983. In the course of field observations it was found that adultM. matrida beetles emerged from the soil at sunset to feed and mate. During the first 20 min of flight, most of the beetles were males. The females emerged shortly afterwards, and aggregations numbering 20–30 individuals with equal proportions of males and females were eventually formed on peanut plants. Laboratory olfactometer bioassays showed that peanut leaves (food) attracted both males and females. Field-trapping experiments and olfactometer studies showed thatM. matrida beetles were highly attracted by live virgin females in the presence of food (cut-up peanut leaves). Another set of field trapping experiments indicated that airborne volatiles produced by live virgin females plus food had the same attracting ability as live virgin females plus food. The attraction exerted by the combination of live virgin females and peanut leave volatiles suggests a synergism effect. Accordingly, we propose a two-stage mechanism of chemical communication in theM. matrida beetles: first, the males cause mechanical damage to the host plant to attract both sexes; later, the females emit attractants (sex pheromone) while eating or shortly thereafter.     

Cuticular Hydrocarbons as Sex Pheromone of the Bee <Emphasis Type="Italic">Colletes cunicularius</Emphasis> and the Key to its Mimicry by the Sexually Deceptive Orchid, <Emphasis Type="Italic">Ophrys exaltata</Emphasis>

Male Colletes cunicularius bees pollinate the orchid, Ophrys exaltata, after being sexually deceived by the orchid’s odor-mimicry of the female bee’s sex pheromone. We detected biologically active volatiles of C. cunicularius by using gas chromatographic–electroantennographic detection (GC-EAD) with simultaneous flame ionization detection. After identification of the target compounds by coupled gas chromatography–mass spectrometry (GC-MS), we performed behavioral tests using synthetic blends of the active components. We detected 22 EAD active compounds in cuticular extracts of C. cunicularius females. Blends of straight chain, odd-numbered alkanes and (Z)-7-alkenes with 21–29 carbon atoms constituted the major biologically active compounds. Alkenes were the key compounds releasing mating behavior, especially those with (Z)-7 unsaturation. Comparison of patterns of bee volatiles with those of O. exaltata subsp. archipelagi revealed that all EAD-active compounds were also found in extracts of orchid labella. Previous studies of the mating behavior in C. cunicularius showed linalool to be an important attractant for patrolling males. We confirmed this with synthetic linalool but found that it rarely elicited copulatory behavior, in accordance with previous studies. A blend of active cuticular compounds with linalool elicited both attraction and copulation behavior in patrolling males. Thus, linalool appears to function as a long-range attractant, whereas cuticular hydrocarbons are necessary for inducing short-range mating behavior.     

Biology of pheromone release by male caribbean fruit flies,Anastrepha suspensa (Diptera: Tephritidae)

Males of the Caribbean fruit fly,Anastrepha suspensa (Loew), typically form leks and attract females by releasing a multicomponent volatile pheromone. Previous reports have identified two nine-carbon alcohols, three lactones, a sesquiterpene, and a monoterpene in the volatiles. The present report is a study of the physiology of male pheromone release and of ecological and social interactions that influence pheromone release by laboratoryreared flies. Volatiles released by males were trapped on Tenax, eluted, separated, and quantitatively measured by gas chromatography. Experiments showed that the volatiles were primarily released from mouth and anus. Sealing the anal opening or the mouth with melted beeswax resulted in up to 40% or greater reduction in most components, and sealing both mouth and anus further reduced release of volatiles, but some volatiles are possibly still released directly from the cuticle. An anal pouch of everted tissue played a major role as a large evaporative surface for release of some of the volatile components. Male flies entrained to a 1410 light-dark cycle showed a peak release of volatiles at 11–12 hr into the photophase, but smaller quantities of the same volatiles were released over a broad period during the daylight hours. Laboratory-reared males peaked in pheromone release at 7–10 days and production and release continued through 35 days of age. Single males released significantly more of all components measured than did groups of males. The reduction by aggregations of males may be related to lekking behavior in this fruit fly. The pheromone probably serves to attract females to a lek site, but additional parameters are likely to enter into the choice of male made by the arriving female.This is University of Florida Agricultural Experiment Station Journal Series No. 9589.