Attraction of female mediterranean fruit flies to the five major components of male-produced pheromone in a laboratory flight tunnel

Attraction and pheromonal activity of five major identified components of the male-produced sex pheromone of the Mediterranean fruit flyCeratitis capitata to virgin laboratory-reared females was assessed in a laboratory flight tunnel. Dual-choice competitive assays were run to establish a baseline response of virgin females to live male pheromone, individual components, and an ensemble of all five compounds alone (air control) and competitively against one another. Approximately 50% of the females released in the tunnel were captured on leaf models emitting pheromonal odors from five live males. Over 37% of released females responded to an ensemble of five major identified components presented in individual capillaries. Response of females to individual components was less than 10%. Competitive assays showed the live male-produced pheromone to be more attractive than either the five major component ensemble (FMCE) or individual components. Further research is likely to identify other male-produced compounds with pheromonal activity that could improve development of a pheromone-based trap for monitoring Mediterranean fruit fly populations.     

Foraging Behavior of Anastrepha Ludens, A. obliqua, and A. serpentina in Response to Feces Extracts Containing Host Marking Pheromone

Following oviposition, females of many Tephritid flies deposit host marking pheromones (HMPs) to indicate that the host fruit has been occupied. We describe the foraging behavior of these three economically important species (Anastrepha ludens and A. obliqua from the fraterculus species group and A. serpentina from the serpentina species group) when they encounter an artificial fruit (green agar spheres wrapped in Parafilm) marked with intra- and interspecific feces extracts that contain, among other substances, host marking pheromone. When flies encountered fruit treated with either 1 or 100 mg/ml feces extract, there were drastic and statistically significant reductions in tree residence time, mean time spent on fruit, and in the number of oviposition attempts or actual ovipositions when compared to the control treatment (clean fruit). These responses were almost identical irrespective of extract origin (i.e., fly species), indicating complete interspecific HMP cross-recognition by all three Anastrepha species tested. We discuss the ecological and practical implications of our findings.     

Evidence for a Host-Marking Pheromone in White Spruce Cone Fly, Strobilomyia neanthracina

Cone flies (Strobilomyia spp.) lay eggs on coniferous cones, and larvae must complete development within the cone on which the eggs are laid. Previous field surveys showed that egg distributions of several species are uniform, suggesting that females avoid ovipositing on cones with conspecific eggs or larvae. In both the field and laboratory, S. neanthracina females walked around cones following oviposition, touching their mouthparts to the cone as they walked. In laboratory bioassays, where females were presented with a cone on which they or another female had oviposited and touched with mouthparts, or one without an egg, females laid preferentially on cones without eggs. However, females laid randomly when presented with a cone on which a female had oviposited but been prevented from touching with her mouthparts following oviposition or another cone without an egg. This indicates that females deposit a host-marking pheromone with their mouthparts following oviposition and that this deters further oviposition on marked hosts. Laboratory and field bioassays indicated that the host-marking pheromone is located in the head and thorax of female flies.     

Larval Diet Affects Male Pheromone Blend in a Laboratory Strain of the Medfly, <Emphasis Type="Italic">Ceratitis capitata</Emphasis> (Diptera: Tephritidae)

The Mediterranean fruit fly (medfly) Ceratitis capitata is a polyphagous pest of fruits and crops with a worldwide distribution. Its ability to use different larval hosts may have multiple effects, including impacts on adult reproductive biology. The male sex pheromone, which plays a key role in attracting both other males to lekking arenas and females for mating, is a mixture of chemical compounds including esters, acids, alkanes and terpenes known to differ between laboratory strains and wild-type populations. The relationship between larval diet and adult pheromone composition remains unexplored. Here, we investigated the effect of larval diet, including laboratory media and fresh fruits, on the composition of the male pheromone mixture. Using Headspace Solid Phase Microextraction we collected the pheromone emitted by males reared as larvae on different substrates and found both qualitative and quantitative differences. A number of alkanes appeared to be typical of the pheromone of males reared on wheat bran-based larval medium, and these may be cuticular hydrocarbons involved in chemical communication. We also detected differences in pheromone composition related to adult male age, suggesting that variations in hormonal levels and/or adult diet could also play a role in determining the chemical profile emitted. Our findings highlight the plasticity of dietary responses of C. capitata, which may be important in determining the interactions of this pest with the environment and with conspecifics. These results also have applied relevance to increase the mating competitiveness of mass-reared C. capitata used in Sterile Insect Technique programs.     

Residual activity of oviposition-deterring pheromone inRhagoletis pomonella (Diptera: Tephritidae) and female response to infested fruit

Under dry conditions, oviposition-deterring pheromone (ODP) of the apple maggot fly (Rhagoletis pomonella Walsh) on host fruit proved deterrent to ovipositing females for at least three weeks, with a half-life of ca. 11 days. There was no difference in decline of residual activity under lab vs. field conditions or between fly-deposited ODP vs. an application of a water extract of ODP. A decline in pheromone activity resulted from exposure to both natural and simulated rainfall. For natural rainfall, greatest losses (50– 61%) in activity resulted from high-intensity rains, with substantially less activity lost (13–35%) following light or moderate intensity rains.R. pomonella females discriminated against fruit without ODP but with conspecific larvae. Discrimination against infested fruit was manifested within fewer days following infestation of small fruit (9 mm diam.) as compared to larger fruit (15 mm diam.).     

Aqueous extracts from indigenous plants as oviposition deterrents forHeliothis virescens (F.)

In laboratory and field tests, water extracts from plant foliage deterred oviposition byHeliothis virescens (F.). A maximum reduction of 93% was attained in laboratory oviposition cages. When females were allowed free choice of treated or untreated tobacco plants in field cage and field tests, maximum reductions in oviposition were 71 and 83%, respectively.Lepidoptera: Noctuidae.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Regulation of Oviposition in Anopheles gambiae s.s.: Role of Inter- and Intra-Specific Signals

Females of Anopheles gambiae Giles normally oviposit in a large number of fresh, small, sunlit, and spatially spread temporary pools. Such pools are associated with lower levels of predation compared to large, longer-lasting habitats. We compared oviposition levels on preferred (water collected from natural anopheline larval habitats) and non-preferred (distilled water) aqueous substrates by gravid females that contained different densities of conspecific eggs or early and late instar larvae. The presence of conspecific larvae, but not eggs, had a positive or negative effect on the ovipositional responses of gravid An. gambiae females, depending on the quality (preferred or non-preferred by the mosquito) of the oviposition water and the density of larvae. Presence of larvae, at all densities, in distilled water deterred oviposition. However, in natural anopheline pool water, a low density of larvae increased oviposition, whereas a higher density inhibited oviposition. Our results suggest that two signals produced by this mosquito may be involved in regulating oviposition: a volatile pheromone emitted by conspecific larvae, which augments the effect of a volatile signal emitted by preferred habitats, and a non-olfactory cue associated with high densities of larvae that deters oviposition.     

Oviposition response of Chironomus tepperi to nitrogenous compounds and bioextracts in two-choice laboratory tests

Two-choice laboratory tests were used to investigate the oviposition response of Chironomus tepperi to a range of nitrogenous compounds and crude bioextracts. Responses to nitrogenous compounds varied in response to concentration. Ammonium nitrate did not influence oviposition at concentrations from 2 to 12 mg/liter. Hydroxylamine hydrochloride increased oviposition at 6 mg/liter, but had no effect at either 2 or 12 mg/liter. Sodium nitrate reduced oviposition at 2 mg/liter relative to the controls, but had no significant effect at 6 or 12 mg/liter. C. tepperi responded to many of the crude bioextracts, strongly avoiding oviposition in solutions containing homogenized chironomid larvae (1 final instar/100 ml; C. tepperi or Polypedilum nubiferum), and avoiding solutions conditioned by conspecificlarvae at concentrations down to the equivalent of 1 final instar/100 ml over 24 hr. Homogenates of adult conspecifics had no effect on oviposition site selection. Homogenates of larval Culex annulirostris (Culicidae) deterred oviposition, but only at high concentrations (3 final instars/100 ml). Our results demonstrate that chemical cues from larval populations deter oviposition by C. tepperi females searching for newly flooded habitats where larval competition will be minimized.     

Floral synomone of a wild orchid,Bulbophyllum cheiri,lures Bactrocera fruit flies for pollination

The major fruit fly attractant component in the floral fragrance of Bulbophyllum cheiri (fruit fly orchid) is methyl eugenol (ME). In the lowland rain forest of Malaysia, the solitary and nonresupinate flowers of the fruit fly orchid attract only males of the ME-sensitive fruit fly species (Bactrocera carambolae, B. papayae, and B. umbrosa. During the morning, the fruit fly orchid flower is visited by many fruit flies, which can sometimes cover the whole flower. The number of visitors dwindles in the afternoon. Headspace analysis of the flower shows a high ME peak in the morning, a small one between 12:00 and 14:00 hr, and no detectable ME peak after 14:00 hr. The process of pollination in the wild is initiated by attraction of fruit flies to floral ME. The flower, with the aid of its specialized hinged see-saw lip (labellum), temporarily traps (<1 min) a fruit fly pollinator between its lip and column. Just prior to this, the fly is rewarded by the opportunity to feed on the floral attractant found on surfaces of petals, sepals, and lip. The pollinaria borne by two wild B. papayae males (caught on and near the fruit fly orchid flower) are identical in morphology and structure with those obtained from the flower. Many of the B. papayae males (17 of 22 analyzed) attracted to the fruit fly orchid already possessed both ME metabolites, trans-coniferyl alcohol and 2-allyl-4,5-dimethoxyphenol, in their rectal glands, indicating that they had previously consumed ME. In this orchid–fruit fly association, both organisms gain direct reproductive benefits: the orchid flower gets pollinated without having to offer nectar, while the fruit fly boosts its pheromone and defense system, as well as its sexual competitiveness by feeding on the ME produced by the flower.     

Factors influencing release of hostmarking pheromone byRhagoletis pomonella flies

The effect of fly or fruit treatments on quality and/or quantity of host-marking pheromone (HMP) trail substance released by apple maggot flies (Rhagoletis pomonella) following oviposition was evaluated. Among flies, considerable variation existed in the amount of HMP substance deposited, but overall, the amount of substance released on successively offered fruit (over a day or a week) did not change appreciably. Fly diet did not influence pheromone activity. Older flies (28 days) or smaller flies released less or less active HMP trail substance than younger flies (14 days) or larger flies. Females deposited a similar amount of trail substance on large (18–19 mm diam.) or HMP-marked fruit as on small (12–13 mm) or unmarked fruit. Starvation reduced the amount of measurable trail substance deposited but resulted in a more active HMP deposition. Discrepancy between trail measurement and behavioral bioassay results for the starvation treatment indicated that trail measurement results may be misleading under conditions that reduce gut contents of the fly.     

Aphid and Plant Volatiles Induce Oviposition in an Aphidophagous Hoverfly

Episyrphus balteatus DeGeer (Diptera, Syrphidae) is an abundant and efficient aphid-specific predator. We tested the electroantennographic (EAG) response of this syrphid fly to the common aphid alarm pheromone, (E)-β-farnesene (EβF), and to several plant volatiles, including terpenoids (mono- and sesquiterpenes) and green leaf volatiles (C6 and C9 alcohols and aldehydes). Monoterpenes evoked significant EAG responses, whereas sesquiterpenes were inactive, except for the aphid alarm pheromone (EβF). The most pronounced antennal responses were elicited by six and nine carbon green leaf alcohols and aldehydes [i.e., (Z)-3-hexenol, (E)-2-hexenol, (E)-2-hexenal, and hexanal]. To investigate the behavioral activity of some of these EAG-active compounds, E. balteatus females were exposed to R-(+)-limonene (monoterpene), (Z)-3-hexenol (green leaf alcohol), and EβF (sesquiterpene, common aphid alarm pheromone). A single E. balteatus gravid female was exposed for 10 min to an aphid-free Vicia faba plant that was co-located with a semiochemical dispenser. Without additional semiochemical, hoverfly females were not attracted to this plant, and no oviposition was observed. The monoterpene R-(+)-limonene did not affect the females’ foraging behavior, whereas (Z)-3-hexenol and EβF increased the time of flight and acceptance of the host plant. Moreover, these two chemicals induced oviposition on aphid-free plants, suggesting that selection of the oviposition site by predatory hoverflies relies on the perception of a volatile blend composed of prey pheromone and typical plant green leaf volatiles.     

Intra- and interspecific sex pheromone responses of screwworm and secondary screwworm flies

A laboratory behavioral assay examined intra- and interspecific responses to sex pheromone by screwworms,Cochliomyia hominivorax, and secondary screwworms,C. macellaria, in relation to the duration of colonization ofC. hominivorax test males. Females ofC. macellaria, like those ofC. hominivorax, were found to produce a pheromone that stimulates male copulatory attempts on contact. Newly colonized (<22 generations)C. hominivorax males did not respond toC. macellaria pheromone, indicating that pheromone contributes to reproductive isolation between these two closely related species. Although long-colonized (>200 generations)C. hominivorax males did respond toC. macellaria females or their extract, this behavior was infrequent and significantly less common than intraspecific responses. DeprivingC. macellaria adults of dietary protein did not affect the potency of female extracts, but did reduce male responsiveness to pheromone. These results provided little evidence that colonization reduces the ability ofC. hominivorax males to differentiate betweenC. hominivorax andC. macellaria females using sex pheromones.     

Oviposition-deterring pheromone ofRhagoletis pomonella

We found that after the parasitoidOpius lectus has arrived on a fruit infested by eggs or early-instar larvae of its tephritid hostRhagoletis pomonella, the following stimuli act to retain it and elicit antennal tapping and oviposition probes: unidentified fruit chemical components; characteristic fruit shape, size and color; andR. pomonella oviposition-deterring pheromone. This is the first demonstration of an oviposition-deterring pheromone in a phytophagous insect serving as a kairomone to one of its parasitoids.O. alloeus, a parasitoid of lateinstar larvae ofR. pomonella, was not influenced by the pheromone. Possible use of the pheromone for management ofO. lectus in a multifacetedR. pomonella suppression program is discussed.     

Host marking pheromone ofRhagoletis cerasi: Foraging behavior in response to synthetic pheromonal isomers

We studied the foraging behavior ofRhagoletis cerasi females in trees treated with synthetic cherry fruit fly host marking pheromone (HMP) under seminatural conditions (potted trees enclosed in a screen cage). Results show that synthetic HMP (particularly the 8RS-@#@ 15R isomer configuration (racemic mixture)) was highly effective in eliciting behavioral responses similar to those reported in studies using natural HMP. Flies exposed to synthetic pheromone exhibited short tree residence times (i.e., emigrated faster), increased flight frequency rates (measured as number of alightings per/minute), higher irritation indices while on a tree or a fruit, and oviposited fewer eggs per fruit visit than flies exposed to clean trees and fruit (not treated with synthetic HMP). Furthermore, we provide evidence showing that when flies were continuously exposed to an HMP-saturated environment, they exhibited an increased tendency to lay eggs in marked fruit.     

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).     

Mutual Reproductive Benefits Between a Wild Orchid, Bulbophyllum patens, and Bactrocera Fruit Flies via a Floral Synomone

The solitary flower of Bulbophyllum patens selectively attracts male fruit flies of several Bactrocera species with a specific fragrance in the rain forest of Malaysia. It temporarily traps flies between its hinged see-saw lip and column for pollination. The attractant component is zingerone [4-(4-hydroxy-3-methoxyphenyl)-2-butanone], a pungent essence of ginger. Zingerone has a structure resembling two major fruit fly attractants (methyl eugenol and raspberry ketone) and shows potency to attract a wide range of fruit fly species (B. carambolae, B. caudata, B. cucurbitae, B. tau, and B. umbrosa). A fruit fly visitor is rewarded by feeding on zingerone, and in return it removes the pollinarium and then transfers it to another flower. Males of the melon fly acquire the floral essence and selectively store it in the pheromone gland to attract conspecific females. Males of B. papayae, however, convert zingerone to zingerol in the crop. The latter compound is stored in the rectal gland and subsequently released to attract females. This provides a rare example of a mutualistic interaction between insects and plants via a floral synomone, in which both organisms obtain advantages directly benefiting their reproductive systems.     

Oviposition Responses of Gravid Female <Emphasis Type="Italic">Culex quinquefasciatus</Emphasis> to Egg Rafts and Low Doses of Oviposition Pheromone Under Semifield Conditions

Semifield experiments were conducted to study the oviposition of gravid Culex quinquefasciatus females in response to one or 10 egg rafts, or 3.0 μg of synthetic oviposition pheromone, (-)-(5R,6S)-6-acetoxy-5-hexadecanolide, a dose equivalent to 10 egg rafts. These treatments were added to the small bowls filled with either hay infusion or water in a small (0.3-m spacing) or a large-square design (3.4-m spacing). Oviposition choice was more pronounced in the “small square” assays. Mean number of egg rafts laid in response to a single egg raft in an oviposition jar filled with hay infusion was significantly greater than with all other treatments. When the oviposition pheromone dose was increased from one to 10 rafts or when 3.0 μg synthetic oviposition pheromone were dispensed on a floating receptacle, synergistic effects were observed between the oviposition pheromone and the hay infusion at both distances. This study is the first demonstration that the amount in a single raft induces oviposition of gravid Cx. quinquefasciatus females under semi-natural conditions.     

Oviposition deterrent by female reproductive gland secretion in Japanese pine sawyer, Monochamus alternatus

Adult females of Monochamus alternatusare known to use palpation to recognize oviposition scars that contain eggs and to be deterred from oviposition. This study investigated the oviposition-deterring activity of a jellylike secretion deposited by the females immediately after oviposition and methanol extracts of female reproductive organs in the laboratory. When females searching for oviposition sites encountered artificial oviposition scars, they stopped walking and drummed the surface and inside of the oviposition scars with their maxillary and labial palpi. When the females encountered the artificial scars plugged with the jellylike secretion, most of them left the scars after palpation. In contrast, when females encountered artificial scars not plugged with the secretion, most of them deposited single eggs through the scars. In another experiment, most females left artificial scars treated with methanol extracts of the spermathecal gland or other reproductive organs after palpation, but most of them oviposited through the scars treated with methanol alone. The results showed that females' recognition of egg-containing scars and departure from such scars were mediated by the chemical(s) produced by their reproductive organs.     

Chemical basis for asymmetric mating isolation between strains of screwworm fly,Cochliomyia hominivorax

Laboratory mating tests and bioassays for a contact, mating-stimulant pheromone were conducted within and between two strains of the screwworm fly,Cochliomyia hominivorax. No strain or sex difference in pheromone activity occurred at emergence. However, the pheromone activity of females increased with age in one strain but declined in the other. Activity also declined in males of both strains but more steeply than in the females. Thus, sexual dimorphism in pheromone activity developed with age in both strains but to differing degrees. The decline in female pheromone activity was partly compensated for within that strain by a higher male responsiveness to pheromone. Female pheromone activity and mating success were positively correlated. Virgin females and those inseminated 24–48 hr previously were equally stimulatory. It appears that the strain differences arose from selection for reduced pheromone activity during laboratory colonization.     

Production of onion fly attractants and ovipositional stimulants by bacterial isolates cultured on onion

Decomposing onions at certain microbial successional stages produce potent volatile attractants and ovipositional stimulants of the onion fly,Delia antiqua (Diptera: Anthomyiidae). A reproducible source of these compounds was obtained by culturingErwinia carotovora var.carotovora (EC) on sterile onion tissue. In laboratory choice tests, EC-inoculated onion was more attractive thanKlebsiella pneumoniae (KP) cultured on onion, EC cultured on potato (a nonhost of onion fly), or the chemical synthetic baits dipropyl disulfide and an aqueous solution of 2-phenylethanol and pentanoic acid. Onion flies were mildly attracted to potato after inoculation with EC, but females did not accept EC-inoculated potato for oviposition. This work emphasizes that sources of semiochemicals may need to be defined microbiologically as well as physically and chemically.Diptera: Anthomyiidae.Paper No. 12106 of the Michigan State University Agricultural Experiment Station.