Zingerone in the floral synomone of Bulbophyllum baileyi (Orchidaceae) attracts Bactrocera fruit flies during pollination

Many orchids use specific volatile chemical(s) in floral fragrance to attract potential pollinators to locate and visit flowers in the tropical rain forests. Male fruit flies (Bactrocera species) are attracted to the ‘fruity odour’ of Bulbophyllum baileyi. The floral chemical component responsible for this fruit fly attraction is zingerone, which also acts as a floral chemical reward during pollination. Zingerone (5 mg), absorbed into a filter and released via a portable-battery operated fan between 0900 and 1100 h, attracted 5–7 males of Bactrocera indonesiae in an orchard located in Kedah, Malaysia. In Penang island, the fruit fly species attracted are Bactrocera dorsalis (methyl eugenol-sensitive) and Bactrocera albistragata (raspberry ketone-sensitive). An attracted male fruit fly probes and feeds on floral petal or sepal before climbing on to the small see-saw lip (labellum). While on the lip and due to shifting of the fly's weight, the fly is toppled head first into the column cavity and simultaneously touches and consequently gets stuck to the sticky viscidium of pollinarium that still remained in the anther. It spends 23–46 min trying to free itself from being suspended from the floral column. Removal of pollinarium (pollinia, stipe and viscidium) is a long process. A male B. dorsalis that fed on a B. baileyi flower was found to sequester zingerol (a reduced form of zingerone) in the body, suggesting its role as sex pheromone to attract a female during courtship behaviour.     

The ecology and evolution of fly dispersed dung mosses (Family Splachnaceae): Manipulating insect behaviour through odour and visual cues

The use of sensory attractants is central to most animal-mediated pollination and seed dispersal interactions. Approximately half the 73 species of mosses’ in the family Splachnaceae are entomophilous (have their spores dispersed by flies) and are coprophilous (grow on feces and carrion). When mature, entomophilous species often produce brightly coloured, scented sporophytes which, for several species, have been shown to attract flies. In a number of cases, sporophyte colours and odours, as well as the flies that visit them, have been shown to be species-specific, suggesting that the mosses co-exist by signal diversification, just as flowering plants are thought to reduce competition for pollinators. Analyses of scent chemistry identified an odour contrast between generations; gametophytes were either unscented or weakly scented in most species, whereas sporophyte odours were universally stronger per unit mass and much more chemically complex. Sporophyte odours of North and South American species sampled were both complex and diverse, with an apparent inverse relationship between the size and showiness of the apophysis and its odour complexity. Furthermore, phylogenetic evidence suggests that fly dispersal of spores through visual and olfactory signals has evolved multiple times in the Splachnaceae and that modifications of sporophyte morphology may have followed, rather than triggered, the transitions to coprophily and entomophily. We review the ecological and evolutionary aspects ofentomophily, with particular emphasis on the chemistry of sporophyte odours and the means by which they mimic decaying organic matter.     

Trap for tephritid fruit fly parasites

A sticky trap for capturing the adults of tephritid fruit fly parasites was designed. This trap consisted of an outer and inner cylinder made of hardware cloth. Host fruits of fruit flies were placed in the inner cylinder and the outer one was sprayed with tanglefoot. Fruit fly adults and parasites attracted to the fruit were captured on the sticky outer cylinder.     

Comparative field studies of various traps and attractants of the olive fruit fly,Bactrocera oleae

In the framework of an ongoing testing and refining process of a mass trapping method, using a combination of semiochemicals, for the control of the olive fruit fly,Bactrocera (Dacus) oleae, four trap designs, three trap colors, six different food attractants, and two pheromone formulations were compared under field conditions. No differences were observed between the trap designs and the food attractants tested. Trap color had a significant effect in preference tests only. Traps combining food attractants and pheromones attracted higher numbers of both male and female flies but the differences became statistically significant only in cases of low trap densities. Pheromones enclosed in cyclodextrenes were not as attractive as standard pheromone formulations. The findings of these tests allow a choice among trap types and semiochemicals for cost reduction and convenience, but not for enhancement of the efficacy of the method.     

Whole body extract of Mediterranean fruit fly males elicits high attraction in virgin females

The search for effective female attractants emanating from the host or body of fruit flies has been an area of intensive research for over three decades. In the present study, bodies of male Mediterranean fruit flies, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), were extracted with diethyl ether or methanol and subjected to gas chromatography–mass spectrometry. Analysis revealed substantial qualitative and quantitative differences between males from a laboratory culture and wild males captured alive in an orchard. Most notably, the hydrocarbon sesquiterpene (±)‐α‐copaene, which is known to be involved in the sexual behaviour of the species, was found in substantial amounts in wild males, but was not detected in laboratory males. In laboratory tests, 15 laboratory or wild male equivalents of diethyl ether extracts or combined diethyl ether and methanol extracts, or, to a lesser extent, methanol extracts alone, were found to attract virgin females. In a citrus orchard, traps baited with combined diethyl ether and methanol extracts of wild males attracted significantly more virgin females than traps baited with various doses of pyranone or blends of other compounds identified in the extracts or reported in the literature, such as ethyl acetate, ethyl‐(E)‐3‐octenoate, and 1‐pyrroline. Traps baited with blends of compounds, however, displayed substantial attractiveness compared to control (non‐baited) traps. These results are important for better understanding the mating system of C. capitata as well as for further improving existing monitoring and control systems.     

Revised irradiation doses to control melon fly, Mediterranean fruit fly, and oriental fruit fly (Diptera: Tephritidae) and a generic dose for tephritid fruit flies

Currently approved irradiation quarantine treatment doses for Bactrocera cucurbitae (Coquillet), melon fly; Ceratitis capitata (Wiedemann), Mediterranean fruit fly; and Bactrocera dorsalis (Hendel), oriental fruit fly, infesting fruits and vegetables for export from Hawaii to the continental United States are 210, 225, and 250 Gy, respectively. Irradiation studies were initiated to determine whether these doses could be reduced to lower treatment costs, minimize any adverse effects on quality, and support a proposed generic irradiation dose of 150 Gy for fruit flies. Dose-response tests were conducted with late third instars of wild and laboratory strains of the three fruit fly species, both in diet and in fruit. After x-ray irradiation treatment, data were taken on adult emergence, and adult female fecundity and fertility. Melon fly was the most tolerant of the three species to irradiation, and oriental fruit fly was more tolerant than Mediterranean fruit fly. Laboratory and wild strains of each species were equally tolerant of irradiation, and larvae were more tolerant when irradiated in fruit compared with artificial diet. An irradiation dose of 150 Gy applied to 93,666 melon fly late third instars in papayas resulted in no survival to the adult stage, indicating that this dose is sufficient to provide quarantine security. Irradiation doses of 100 and 125 Gy applied to 31,920 Mediterranean fruit fly and 55,743 oriental fruit fly late third instars, respectively, also resulted in no survival to the adult stage. Results support a proposed generic irradiation quarantine treatment dose of 150 Gy for all tephritid fruit flies.     

Sequestration of 3-oxygenated α-ionone derivatives in the male rectal gland of the solanaceous fruit fly, Bactrocera latifrons

The solanaceous fruit fly, Bactrocera latifrons (Hendel) (Diptera: Tephritidae), infests various solanaceous fruits including eggplant and chili peppers. We found that a freshly cut fruit of an eggplant cultivar [ Solanum melongena L. cv. Long Purple Oriental (Solanaceae)] selectively attracted and provoked voracious feeding behavior in adult B. latifrons males (but not in females) in an indoor test. One of the male-specific attractants/feeding stimulants in eggplant was identified as 3-hydroxy-α-ionone. Sexually mature males that fed on the eggplant pulp selectively accumulated a series of 3-oxygenated α-ionone/α-ionol analogs (e.g., 3-oxo-α-ionol and 3-oxo-7,8-dihydro-α-ionol) in the rectal gland, a suspected pheromone reservoir in male flies. Males fed on synthetic 3-hydroxy-α-ionone, 3-oxo-α-ionol, or 3-oxo-α-ionone partially biotransformed the compounds into 3-oxo-α-ionol, 3-oxo-α-ionone, and 3-oxo-7,8-dihydro-α-ionol and sequestered substantial quantities (as high as 5 µg/gland as a mixture) in a similar ratio in the rectal gland within 6 h after ingestion. These results suggest that the rectal sequestrates may serve as a sex pheromone similar to other Bactrocera species that use phenylpropanoid volatiles to attract conspecific females.     

Attraction of Drosophila melanogaster males to food-related and fly odours

The fruit fly Drosophila melanogaster has become a model for olfaction and odour-mediated behaviour. In the wild, Drosophila flies aggregate on decaying fruit where they mate and oviposit and a strategy to find mates would be to locate fruit which has already been colonized by other flies. We therefore developed a bioassay to investigate attraction of males to food and fly odours. We showed that upwind flights are initiated by food odours. At shorter distances, males are attracted by volatiles produced by conspecifics. However, only odours produced by copulating flies attract males. This suggests either a synergistic effect of both male and female odours or changes in pheromone release during mating, that indicate the presence of sexually receptive females. Our findings demonstrate the essential role of food odours and pheromones for mate location in D. melanogaster.     

Cues used by the black fly,Simulium annulus,for attraction to the common loon (Gavia immer)

The parasitic relationship between a black fly, Simulium annulus, and the common loon (Gavia immer) has been considered one of the most exclusive relationships between any host species and a black fly species. To test the host specificity of this blood‐feeding insect, we made a series of bird decoy presentations to black flies on loon‐inhabited lakes in northern Wisconsin, U.S.A. To examine the importance of chemical and visual cues for black fly detection of and attraction to hosts, we made decoy presentations with and without chemical cues. Flies attracted to the decoys were collected, identified to species, and quantified. Results showed that S. annulus had a strong preference for common loon visual and chemical cues, although visual cues from Canada geese (Branta canadensis) and mallards (Anas platyrynchos) did attract some flies in significantly smaller numbers.     

Susceptibility of low-chill blueberry cultivars to Mediterranean fruit fly, oriental fruit fly, and melon fly (Diptera: Tephritidae)

No-choice tests were conducted to determine whether fruit of southern highbush blueberry, Vaccinium corymbosum L., hybrids are hosts for three invasive tephritid fruit flies in Hawaii. Fruit of various blueberry cultivars was exposed to gravid female flies of Bactrocera dorsalis Hendel (oriental fruit fly), Ceratitis capitata (Wiedemann) (Mediterranean fruit fly), or Bactrocera cucurbitae Coquillet (melon fly) in screen cages outdoors for 6 h and then held on sand in the laboratory for 2 wk for pupal development and adult emergence. Each of the 15 blueberry cultivars tested were infested by oriental fruit fly and Mediterranean fruit fly, confirming that these fruit flies will oviposit on blueberry fruit and that blueberry is a suitable host for fly development. However, there was significant cultivar variation in susceptibility to fruit fly infestation. For oriental fruit fly, 'Sapphire' fruit produced an average of 1.42 puparia per g, twice as high as that of the next most susceptible cultivar 'Emerald' (0.70 puparia per g). 'Legacy', 'Biloxi', and 'Spring High' were least susceptible to infestation, producing only 0.20-0.25 oriental fruit fly puparia per g of fruit. For Mediterranean fruit fly, 'Blue Crisp' produced 0.50 puparia per g of fruit, whereas 'Sharpblue' produced only 0.03 puparia per g of fruit. Blueberry was a marginal host for melon fly. This information will aid in development of pest management recommendations for blueberry cultivars as planting of low-chill cultivars expands to areas with subtropical and tropical fruit flies. Planting of fruit fly resistant cultivars may result in lower infestation levels and less crop loss.     

A potential field suppression system for Bactrocera dorsalis Hendel

Development of an effective and safe detection or control system is important for pest management. Attractants for male fruit flies, e.g., methyl eugenol (ME), are currently being used in fruit fly control in combination with insecticides. A single formulation that possesses both attraction and killing properties would improve control methods and cost effectiveness. We previously observed the attraction of oriental fruit flies to a basil plant in a yard and confirmed the attraction of male fruit flies to basil oil (BO) in the laboratory. Subsequently, we identified insecticidal compounds from BO that killed three species of tephritid fruit flies in the laboratory, and we also discovered physiological interactions between BO constituents and male attractants. Based on these observations, we developed a single package of basil oil and methyl eugenol (BO + ME) formulation that possesses “attract and kill” properties in combination with a modified AWPM standard trap for field application. The effectiveness of this system is dependent on the type of trap and weather conditions (sunny or not sunny). Any attracted flies were killed within 2 h after entering the BO + ME trap. The combination of BO, ME, and a clear bucket trap may be a novel alternative for a cost effective and environmentally friendly fruit fly management system.     

Trap capture of three economically important fruit fly species (Diptera: Tephritidae): evaluation of a solid formulation containing multiple male lures in a Hawaiian coffee field

Invasive fruit flies (Diptera: Tephritidae) pose a global threat to agriculture through direct damage to food crops and the accompanying trade restrictions that often result. Early detection is vital to controlling fruit flies, because it increases the probability of limiting the growth and spread of the invasive population and thus may greatly reduce the monetary costs required for eradication or suppression. Male-specific lures are an important component of fruit fly detection, and three such lures are used widely: trimedlure (TML), cue lure (CL), and methyl eugenol (ME), attractive to Mediterranean fruit fly, Ceratitis capitata (Wiedemann); melon fly, Bactrocera cucurbitae (Coquillett); and oriental fruit fly, Bactrocera dorsalis (Hendel), respectively. In California, Florida, and Texas, the two Bactrocera lures are applied to separate species-specific traps as liquids (with a small amount of the insecticide naled added), whereas TML is delivered as a solid plug in another set of traps. Thus, the detection protocol involves considerable handling time as well as potential contact with a pesticide. The purpose of this study was to compare trap capture between liquid male lures and "trilure" wafers that contain TML, ME, raspberry ketone (RK, the hydroxy equivalent of CL), and the toxicant DDVP embedded within a solid matrix. Field studies were conducted in a Hawaiian coffee (Coffea arabica L.) field where the three aforementioned species co-occur, showed that the wafer captured at least as many flies as the liquid baits for all three species. This same result was obtained in comparisons using both fresh and aged (6-wk) baits. Moreover, the wafers performed as well as the single-lure traps in an ancillary experiment in which TML plugs were substituted for liquid TML. Additional experiments demonstrated explicitly that the presence of ME and RK had no effect on captures of C. capitata males and similarly that the presence of TML had no effect on the capture of B. cucurbitae or B. dorsalis males.     

Host shifts in economically significant fruit flies (Diptera: Tephritidae) with high degree of polyphagy

Insects tend to feed on related hosts. Coevolution tends to be dominated by interactions resulting from plant chemistry in defense strategies, and evolution of secondary metabolisms being in response to insect herbivory remains a classic explanation of coevolution. The present study examines whether evolutionary constraints existing in host associations of economically important fruit flies in the species‐rich tribe Dacini (Diptera: Tephritidae) and to what extent these species have evolved specialized dietary patterns. We found a strong effect of host phylogeny on associations on the 37 fruit flies tested, although the fruit fly species feeding on ripe commercially grown fruits that lost the toxic compounds after long‐term domestication are mostly polyphagous. We assessed the phylogenetic signal of host breadth across the fruit fly species, showing that the results were substantially different depending on partition levels. Further, we mapped main host family associations onto the fruit fly phylogeny and Cucurbitaceae has been inferred as the most likely ancestral host family for Dacini based on ancestral state reconstruction.     

Synergistic and additive interactions among components of food-based baits underlie female fruit fly attraction

Attraction of tephritid fruit flies to some food sources can be enhanced by the presence of ammonia derivatives, compounds that are perceived as volatile cues for protein-rich food sources. Using a comparative approach, we (1) evaluated the behavioral responses of females of three invasive fruit fly species, Bactrocera (Zeugodacus) cucurbitae (Coquillett), Bactrocera dorsalis (Hendel), and Ceratitis capitata (Wiedemann) (all Diptera: Tephritidae) to trub (a protein-rich waste brewer’s yeast product generated during the production of beer), Concord grape juice (a protein-deficient material), and ammonium acetate, and (2) identified synergistic and additive interactions between low- and high-attractiveness materials and ammonium acetate. We established the attractiveness of fresh trub, grape juice, and ammonium acetate when tested singly to females of all three fly species. Although ammonium acetate did not enhance significantly the response of females of any species to fresh trub, the most attractive material, ammonium acetate, did significantly enhance females’ level of response to aged trub (a comparatively less attractive material) and to grape juice. Our research found a synergistic interaction between diluted grape juice and ammonium acetate for B. cucurbitae, as well as between aged trub and ammonium acetate for B. dorsalis. For C. capitata, additive effects among food attractants and ammonium acetate were identified. Our findings increase our understanding of fruit fly female olfactory-driven behavior in response to food-based materials and the extent to which ammonium acetate modulates female response to protein-rich and protein-deficient materials.     

Field comparison of chemical attractants and traps for Caribbean fruit fly (Diptera: Tephritidae) in Florida citrus

Field studies in citrus were conducted to compare the following as attractants for the Caribbean fruit fly, Anastrepha suspensa (Loew): torula yeast-borax; propylene glycol (10%); a two-component lure consisting of ammonium acetate and putrescine; a two-component lure consisting of ammonium bicarbonate and putrescine; and a three-component lure consisting of ammonium bicarbonate, methylamine hydrochloride, and putrescine. Various combinations of these attractants in glass McPhail, plastic McPhail-type (Multi-Lure), and sticky panel traps were investigated in two replicated studies. In one study on wild flies, the most effective and least complex trap-lure combination tested was the Multi-Lure with propylene glycol baited with ammonium acetate and putrescine. This trap-lure combination captured significantly more female and male flies than the standard glass McPhail baited with torula yeast-borax in water. All of the trap-lure combinations were female biased, with an overall average of 80.8% (SEM 1.4) flies captured being female. A second study on laboratory-reared, irradiated flies indicated no significant differences among these trap-lure combinations with respect to number of flies recaptured, although rankings based on mean number of flies recovered per trap per day supported results of the first study. The percentage of flies recaptured that were female (83.0%, SEM 0.9) was statistically the same as in the first study. Weekly percentage recovery of flies during the second study was low, possibly due to our fly release strategy. Future release/recovery studies with laboratory-reared flies would benefit from some basic research on release strategies by using different trap densities and on relating recapture rates of laboratory-reared flies (nonsterile and sterile) to capture rates of wild flies.     

The fruit fly PUB: a phagostimulation unit bioassay system to quantitatively measure ingestion of baits by individual flies

Abstract:  A bioassay to investigate quantitative phagostimulation and ingestion physiology of baits on individual fruit flies is presented. The study was undertaken using two fruit fly species: the Mediterranean fruit fly ( Ceratitis capitata ), a cosmopolitan insect pest, and the Ethiopian fruit fly ( Dacus ciliatus ), a quarantine insect in Israel. Our model bait suspension included spinosad as the toxic agent, and 1% yeast hydrolysate with 10% sucrose as phagostimulant. A preliminary toxicology study showed that the two fruit flies are highly sensitive to low concentrations of spinosad baited with this phagostimulant. The maximum concentration needed to kill 90% of the female flies was 4.2 and 8.5 p.p.m. for C. capitata and D. ciliatus , respectively. The bioassay was able to detect the ingestion of low volumes (e.g. 1  μ l) of tested solutions. The bioassay was also able to detect differences in intake of different concentrations of spinosad solutions and relate ingestion to fruit fly mortality. Additionally, the bioassay was sensitive enough to highlight differences in intake related to the physiological status of the fruit fly and fly species. The bioassay can also be used to follow ingestion kinetics of baits. We expect that this bioassay will contribute in the exploration of more efficient bait systems for fruit flies.     

兰科植物欺骗性传粉

植物与传粉动物的互利关系在生态系统中非常普遍。然而,有许多植物不为传粉者提供任何报酬,而是利用各种欺骗方式诱骗昆虫拜访,从而实现传粉,即欺骗性传粉。兰科是被子植物大科之一,其高度特化的繁殖器官和适应于昆虫传粉的精巧结构令人称奇。进化论创始人达尔文描述了许多兰花与昆虫精巧的传粉系统,但他忽视了欺骗性传粉的存在。事实上,近1/3的兰科植物都依赖于欺骗性传粉。欺骗性传粉可能是导致兰科植物多样性的重要原因之一。兰花利用或操作昆虫觅食、交配、产卵和栖息等行为,演化出各种各样的欺骗性传粉机制,常见的类型包括泛化的食源性欺骗、Batesian拟态、性欺骗、产卵地拟态和栖息地拟态。花的颜色、形态和气味在欺骗性传粉的成功实现中起到了重要作用。欺骗性兰花与传粉昆虫之间的演化可能是不同步的,兰花追踪昆虫的行为信号而发生分化,然而欺骗性传粉可能对昆虫造成一定的伤害,从而对昆虫也施加选择压力。由于昆虫的学习行为,欺骗性的兰花一般具有低的昆虫拜访率和结实率,其繁殖成功率受各种因素的影响。欺骗性加剧了兰花对传粉昆虫的依赖,使其具有更高的灭绝风险,传粉生物学的研究能为兰科植物的有效保护提供指导。在欺骗性传粉系统中,有报酬的伴生植物、拟态模型和其他拟态信号提供者对传粉成功有重要影响。因此,研究欺骗性传粉兰花、传粉昆虫和相关的生物和生态因子的网状进化关系具有重要理论和实践意义。     

Volatile host fruit odors as attractants for the oriental fruit fly (Diptera: Tephritidae)

We examined the responses of oriental fruit flies, Bactrocera dorsalis Hendel, to the odors of different stages and types of fruit presented on potted trees in a field cage. Females were most attracted to odors of soft, ripe fruit. Odors of common guava were more attractive to females than papaya and starfruit, and equally as attractive as strawberry guava, orange, and mango. In field tests, McPhail traps baited with mango, common guava, and orange captured equal numbers of females. Traps baited with mango were compared with 2 commercially available fruit fly traps. McPhail traps baited with mango captured more females than visual fruit-mimicking sticky traps (Ladd traps) and equal numbers of females as McPhail traps baited with protein odors. Results from this study indicate that host fruit volatiles could be used as lures for capturing oriental fruit flies in orchards.     

Evidence for pollinator sharing in Mediterranean nectar-mimic orchids: absence of premating barriers?

Pollinator specificity has traditionally been considered the main reproductive isolation mechanism in orchids. Among Mediterranean orchids, however, many species attract and deceive pollinators by mimicking nectar-rewarding plants. To test the extent to which deceptive orchid species share pollinators, we collected and identified hemipollinaria-carrying insects, and used ribosomal sequences to identify the orchid species from which hemipollinaria were removed. We found that social and solitary bees, and also flies, carried hemipollinaria belonging to nine orchid species with different degrees of specialization. In particular, Anacamptis morio, Dactylorhiza romana and Orchis mascula used a large set of pollinator species, whereas others such as Orchis quadripunctata seemed to be pollinated by one pollinator species only. Out of the insects with hemipollinaria, 19% were found to carry hemipollinaria from more than one orchid species, indicating that sympatric food-deceptive orchids can share pollinators. This sharing was apparent even among orchid sister-species, thus revealing an effective overlap in pollinator sets among closely related species. These results suggest varying degrees of pollinator specificity in these orchids, and indicate that pollinator specificity cannot always act as the main isolation mechanism in food-deceptive temperate orchids.