Laboratory Olfactometer Research Articles

Irresistible bouquet of death—how are burying beetles (Coleoptera: Silphidae: Nicrophorus) attracted by carcasses

Chemical composition of volatiles emitted from fresh mouse carcasses (laboratory mice, Mus musculus) was studied using solid sample injection technique (solid-phase micro-extraction), two-dimensional gas chromatography with time of flight mass spectrometric detection and gas chromatography with electroantennographic detection. Electroantennography (EAG) and laboratory olfactometric behavioural observations were used to study the antennal sensitivity to identified infochemicals and their attractiveness for burying beetles Nicrophorus vespillo and Nicrophorus vespilloides (Silphidae: Nicrophorinae). Chemical analysis showed that immediately after death, emitted volatiles did not differ from those emitted by a living organism. However, in the course of time, sulphur-containing chemicals, specifically methanethiol, methyl thiolacetate, dimethyl sulphide, dimethyl disulphide and dimethyl trisulphide appear. EAG measurements revealed antennal sensitivity to these compounds. Behavioural tests in laboratory olfactometer showed that dimethyl sulphide, dimethyl disulphide and dimethyl trisulphide are highly attractive to both studied species. The data suggest that sulphur-containing chemicals are involved in mediating the fresh carcass attractiveness for N. vespillo and N. vespilloides.

A Male-produced Sex Pheromone from the Neotropical Redbanded Stink Bug, Piezodorus guildinii (W.)

The male-produced sex pheromone of the neotropical redbanded stink bug, Piezodorus guildinii (W.) (Hemiptera: Pentatomidae), a serious pest of soybean in Central and South America, was identified as the sesquiterpene hydrocarbon beta-sesquiphellandrene by coupled gas chromatography-mass spectrometry and laboratory bioassays. The identity was confirmed by comparison with an authentic standard, and its absolute configuration was determined to be (7R)-(+)-beta-sesquiphellandrene. The mean rate of release was approximately 40 ng d(-1) male(-1). The compound was found only in extracts from sexually mature males. Laboratory olfactometer bioassays showed that 200 ng of the synthetic compound applied to a filter paper strip was as attractive to female bugs as odors from five 15-d-old live males, an airborne extract from males, or the fraction of the extract that contained (7R)-(+)-beta-sesquiphellandrene.

Males of <I>Hylamorpha elegans</I> Burmeister (Coleoptera: Scarabaeidae) Are Attracted to Odors Released from Conspecific Females

The behavioral responses of Hylamorpha elegans L. (Coleoptera: Scarabaeidae, Rutelinae) to the semiochemicals released from conspecific individual adults were studied, with particular attention paid to female attraction of males. Odors released from virgin females significantly attracted male conspecifics in both the field and laboratory olfactometer and wind tunnel bioassays. However, females did not attract other females, and males attracted no one. The response of male H. elegans to (1) compounds (1,4-hydroquinone and 1,4-benzoquinone) released only by unmated females; (2) the essential oil of the secondary host (Nothofagus obliqua); and (3) the blend of 1,4-hydroquinone and 1,4-benzoquinone with N. obliqua essential oil was studied. The blend of 1,4-benzoquinone mixed with essential oil at the trial concentration was attractive with males. The same response was found with 1,4-hydroquinone alone. The essential oil did not have the expected attractant effect on conspecific males. These results suggest that, when combined with essential oil, 1,4-benzoquinone may function in the sexual behavior of males and females. These findings are discussed in terms of the ecological role of this putative sexual pheromone and its potential use in a strategy of control of this pest.

Males of Hylamorpha elegans Burmeister (Coleoptera: Scarabaeidae) Are Attracted to Odors Released from Conspecific Females

The behavioral responses of Hylamorpha elegans L. (Coleoptera: Scarabaeidae, Rutelinae) to the semiochemicals released from conspecific individual adults were studied, with particular attention paid to female attraction of males. Odors released from virgin females significantly attracted male conspecifics in both the field and laboratory olfactometer and wind tunnel bioassays. However, females did not attract other females, and males attracted no one. The response of male H. elegans to (1) compounds (1,4-hydroquinone and 1,4-benzoquinone) released only by unmated females; (2) the essential oil of the secondary host (Nothofagus obliqua); and (3) the blend of 1,4-hydroquinone and 1,4-benzoquinone with N. obliqua essential oil was studied. The blend of 1,4-benzoquinone mixed with essential oil at the trial concentration was attractive with males. The same response was found with 1,4-hydroquinone alone. The essential oil did not have the expected attractant effect on conspecific males. These results suggest that, when combined with essential oil, 1,4-benzoquinone may function in the sexual behavior of males and females. These findings are discussed in terms of the ecological role of this putative sexual pheromone and its potential use in a strategy of control of this pest.

Pheromone-Based Attractant for Males of <I>Cactoblastis cactorum</I> (Lepidoptera: Pyralidae)

The cactus moth, Cactoblastis cactorum (Berg), is an invasive pest of Opuntia spp. Since its arrival in the Florida Keys in 1989, it has moved rapidly up the east and west coasts of Florida, threatening to invade the southwestern United States and Mexico. Female moths produce a sex pheromone that attracts male moths. In this study, we report on mating behavior observed in the laboratory and the identification of putative pheromonal chemical components based on mass spectral analysis of volatiles collected from virgin female moths and from solvent extraction of excised glands. Three candidate components, formulated on rubber septa in different release rates and ratios, were tested in laboratory olfactometer and flight tunnel experiments, and in field tests in areas with known feral populations of cactus moths. Lures formulated with the three-component blend of 54% (Z,E)-9,12 tetradecadien-1-ol acetate, 42% (Z,E)-9,12 tetradecadien-1-ol, and 4% (Z)-9- tetradecen-1-ol acetate were the most effective, although changes in the ratio of these components had little effect on lure efficacy. For field deployment, traps baited with synthetic lures with a 1 mg load of the three component blend captured equal or higher numbers of males than traps baited with two virgin females. Trapping systems using this pheromone-based attractant will be useful for population delineation in areas currently infested.

Influence of dung volatiles on the process of resource selection by coprophagous beetles

Most dung beetles colonize the faeces of several vertebrate species without much discrimination, and are thus often considered as polyphagous. Recent studies have provided evidence for clear feeding preferences in scarab beetles colonizing dung of herbivore species, but little is known about these insects’ abilities to discriminate among odours from faeces of various herbivores. In this study, trophic preferences were examined using blocks of pitfall traps baited with dung from four different herbivore species, i.e., sheep, cattle, horse, and red deer, in a mountainous area of south-central France. 4941 coprophagous scarabs, belonging to 27 species, were captured. Beetles were more attracted to dung of sheep (2257 individuals) than that of cattle (1294 individuals), followed by deer dung (768 individuals) and horse dung (622 individuals). Eleven of the 27 beetle species collected had significant feeding preferences for one of the four dung types. For each insect species, trophic habits did not vary between the two different sites of trapping, an open pasture and a wooded habitat. In laboratory olfactometer bioassays, scarab beetles orientated preferentially towards the dung volatiles from the dung type they preferred in the field. Trypocopris pyrenaeus, Anoplotrupes stercorosus, and Aphodius rufipes were more attracted to volatile compounds from sheep dung, Onthophagus fracticornis significantly preferred horse dung volatiles, and Aphodius haemorrhoidalis responded positively to deer dung odours. The role of dung olfactory cues in the process of resource selection by dung beetles is discussed.

ATTRACTION, FEEDING, AND REPELLENCY RESPONSES IN MUTANT STRAINS OF AEDES AEGYPTI1

In a laboratory olfactometer, 12% of female Aedes aegypti with a marker gene for red eye (re), 0.7% of females with a marker gene for white eye (we), and 54.1% of females with normal (norm) eye color were attracted to odor from a human hand. When a synthetic attractant blend was used in place of the hand, the attraction rate was 7%, 0.3%, and 35.4%, respectively. On average, re females required significantly less time (76.8 sec) than we (189.6 sec) or norm (176.7 sec) females to locate, land on, and probe human skin but no difference was found between mosquito strains in the time required for females to bloodfeed to repletion on a restrained guinea pig. Differences among mosquito strains in the repellency of 15% diethyltoluamide (deet), 6.65% deet, and 10% citronella were not significant.

Mastrus ridibundus parasitoids eavesdrop on cocoon-spinning codling moth, Cydia pomonella, larvae

Cocoon-spinning larvae of the codling moth, Cydia pomonella L. (Lepidoptera: Olethreutidae) employ a pheromone that attracts or arrests conspecifics seeking pupation sites. Such intraspecific communication signals are important cues for illicit receivers such as parasitoids to exploit. We tested the hypothesis that the prepupal C. pomonella parasitoid Mastrus ridibundus Gravenhorst (Hymenoptera: Ichneumonidae) exploits the larval aggregation pheromone to locate host prepupae. In laboratory olfactometer experiments, female M. ridibundus were attracted to 3-day-old cocoons containing C. pomonella larvae or prepupae. Older cocoons containing C. pomonella pupae, or larvae and prepupae excised from cocoons, were not attractive. In gas chromatographic-electroantennographic detection (GC-EAD) analyses of bioactive Porapak Q extract of cocoon-derived airborne semiochemicals, ten compounds elicited responses from female M. ridibundus antennae. Comparative GC-mass spectrometry of authentic standards and cocoon-volatiles determined that these compounds were 3-carene, myrcene, heptanal, octanal, nonanal, decanal, (E)-2-octenal, (E)-2-nonenal, sulcatone, and geranylacetone. A synthetic 11-component blend consisting of these ten EAD-active compounds plus EAD-inactive (+)-limonene (the most abundant cocoon-derived volatile) was as effective as Porapak Q cocoon extract in attracting both female M. ridibundus and C. pomonella larvae seeking pupation sites. Only three components could be deleted from the 11-component blend without diminishing its attractiveness to M. ridibundus, which underlines the complexity of information received and processed during foraging for hosts. Mastrus ridibundus obviously "eavesdrop" on the pheromonal communication signals of C. pomonella larvae that reliably indicate host presence.

Semiochemicals from fungal associates of bark beetles may mediate host location behavior of parasitoids.

In laboratory olfactometer bioassays, females of two hymenopteran parasitoid species, Roptrocerus xylophagorum (Ratzeburg) (Hymenoptera: Pteromalidae) and Spathius pallidus (Ashmead) (Hymenoptera: Braconidae), were attracted to odors from bark or bolts of loblolly pine, Pinus taeda L., colonized by bluestain fungi (genus Ophiostoma) associated with the parasitoids' bark beetle hosts. Mock-inoculated bolts and bark were less attractive or unattractive in these bioassays. Bark infested with host larvae that lacked their fungal and other normal microbial associates was attractive to R. xylophagorum females, but was less so than bark infested with larvae possessing their normal complement of associated microbes. In contrast, in oviposition bioassays, R. xylophagorum females spent approximately equal time searching, made similar numbers of oviposition attempts, parasitized similar percentages of hosts, and laid similar numbers of eggs in bark fragments infested with either associate-free or associate-bearing host larvae. Furthermore, in field bioassays using bluestain-inoculated or mock-inoculated loblolly pine bolts as sources of attractants, the numbers of parasitoids attracted by the two treatments did not differ significantly and the two treatments were less attractive than bolts naturally infested with bark beetle larvae. Whereas our laboratory olfactometer data suggest that bark beetle fungal associates may enhance attraction of some parasitoids, our bioassays with associate-free hosts indicate that associate-produced are not required for short-range host location and parasitization. In addition, our field trials indicated that long-range attraction of parasitoids to the host-fungi-tree complex is not caused simply by an interaction between bluestain fungi and tree tissues.

Trophic Preferences Mediated by Olfactory Cues in Dung Beetles Colonizing Cattle and Horse Dung

Scarab beetles colonizing vertebrate feces are considered polyphagous insects, because they often use dung of several species. However, recent works have provided evidence for strong feeding preferences in some dung beetle species. The influence of dung odors in the process of resource selection by beetles has not received attention. The objective of this study was to investigate trophic preferences in Mediterranean dung beetles colonizing cattle and horse dung. The pattern of resource use by insects was studied using series of pitfall traps baited with cattle or horse dung in three different sites of south-central France. A total of 4,276 insects belonging to 39 species were captured. Cattle dung attracted more insects than horse feces (2,570 versus 1,706 individuals). Twenty-four of the 39 beetle species collected had clear feeding preferences for cattle dung (13 species) or horse dung (11 species). None of these species seemed linked exclusively to one kind of dung. The behavioral responses of seven scarab beetles to volatile compounds emitted by cattle and horse dung were compared in laboratory olfactometer bioassays. Three insect species (Aphodius erraticus, A. scrutator, Onthophagus vacca) were more attracted to volatile compounds from cattle dung. Two other species (Euonthophagus amyntas, Bubas bubalus) orientated preferentially toward horse dung volatiles. Except for two species, beetles were thus attracted to volatiles from the dung type they preferred in the field. The reasons why coprophagous beetles show local feeding preferences for particular dung types are discussed.

Stimulatory Beetle Volatiles for the Asian Longhorned Beetle, Anoplophora glabripennis (Motschulsky)

Two male-specific beetle volatiles were found that elicited strong gas chromatographic-electroantennographic responses from both sexes of Asian longhorned beetle adults, Anoplophora glabripennis. The secretion consisted of a approximately 1:1 (v/v) blend of functionalized dialkyl ethers, 4-(n-heptyloxy)butanal and 4-(n-heptyloxy)butan-1-ol. These compounds are chemically unusual natural products that are previously unknown from insects. Laboratory olfactometer studies showed that a blend of 10 microg of each synthetic compound on a filter paper strip was significantly attractive to ALB adults.

Attractiveness of insecticide baits for cockroach control (Dictyoptera: Blattellidae): laboratory and field studies.

Several insecticide bait formulations were evaluated for their attractiveness to cockroaches in olfactometer assays in the laboratory and in trapping experiments in the field. Included in the assays were bait stations, gels, pastes, and a powder that contained one of the following active ingredients: abamectin, boric acid, chlorpyrifos, or hydramethylnon. There were significant differences among the baits in their attractiveness to the German cockroach, Blattella germanica (L.). In trapping experiments, Avert powder (abamectin), Maxforce station and gel, and Siege gel (all hydramethylnon) were consistently attractive to B. germanica adults and nymphs. Laboratory olfactometer assays with adult males confirmed these results and showed that nymphs were as responsive as males whereas females were less responsive. Our bioassays also demonstrate that attractiveness of bait can be dramatically affected by the age of the bait. One week of aging significantly reduced the attractiveness of Avert powder in both laboratory and field assays. Aging, however did not diminish the attractiveness of Maxforce gel, indicating that the formulation may be critical for retention of attractiveness of baits. Baits that were most attractive to the German cockroach were also the most attractive to nymphs and adults of the brownbanded cockroach, Supella longipalpa (F.).

Response of parasitoids Dendrosoter protuberans and Cheiropachus quadrum to attractants of Phloeotribus scarabaeoides in an olfactometer.

The braconid Dendrosoter protuberans and the pteromalid Cheiropachus quadrum are two parasitoids of the olive bark beetle, Phloeotribus scarabaeoides. Several chemicals such as α-pinene, β-pinene, 2-decanone, 2-nonanone, decanal, undecanal, and n-butyl acetate have been identified as attractants in the laboratory for this scolytid. Under red light at 27°C in a laboratory olfactometer both parasitoids oriented positively to both enantiomers of α-pinene, and females also responded to 2-decanone. Significant responses did not occur under white light or at lower temperatures. These results suggest that α-pinene and 2-decanone could be involved in the location of P. scarabaeoides by its parasitoids. Consequently an attracticidal control tactic for this scolytid that included these chemicals could eliminate part of the parasitoid population. In an integrated pest management program, this problem should be considered.

Trapping of the coffee berry borer Hypothenemus hampei Ferr. (Col., Scolytidae) within a mesh‐enclosed environment: interaction of olfactory and visual stimuli

AbstractCoffee berry borer (CBB) colonizing females were released within a mesh‐tent and recaptured in traps to study the interaction of olfactory and visual stimuli during the flight phase. A 1:1 methanol–ethanol mixture was used as an attractant in traps constructed from multiple funnels of red or white. The first aim of the present experiments was to verify that the results obtained in a laboratory olfactometer, in which insects were constrained to walk and in which visual and olfactory stimuli were independently manipulated, could be extended to an outdoor arena enclosed by a net tent. The second aim was to test different emission odour rate, and finally develop a prototype trap which could be used for subsequent studies of CBB population dynamics in the field. Out of 3 000 females released, over 45% were recaptured, among which 95% were collected from traps with methanol–ethanol mixture. The red traps were more attractive than the white traps. The lower the rate of emission of odour, the greater the number of females recaptured. These results show the importance of vision and olfaction for the CBB's flight approach to the trap.

( Z, E)- α-Farnesene—An electroantennogram-active component of Maladera matrida volatiles

It has previously been shown in field-trapping experiments and laboratory olfactometer bioassays that virgin females of Maladera matrida Argaman (Coleoptera, Scarabaeidae) and their volatiles, both in the presence of food (cut peanut leaves), are efficient attractants for M. matrida males and females. In this study GC-EAD experiments using male antennae and GC-MS experiments revealed that ( Z, E)- α-farnesene is an active component of M. matrida female volatiles. The identification and quantitative electrophysiological responses (EAG) of synthetic ( Z, E)- α-farnesene were obtained with male and female antennae. It was also shown that Z, E)- α-farnesene is not a component of the plant volatiles that serve as synergistic components of the mixture of attractants or of the source of food for M. matrida.

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.

Pheromone-based assortative mating in a bark beetle

Abstract. Assortative mating based on a courtship signal was investigated by examining the relationship between the male-produced pheromone and female preference in the bark beetle, Ips pini. Female preference in response to the male-produced pheromone was measured in the field using traps baited with a range of 11 synthetic blends of the two pheromone enantiomers, (+) and (-)ipsdienol. The production of ipsdienol enantiomers was measured from individual, live-trapped male beetles in the laboratory. Although there was a significant regression of the blend that male beetles produced and the blend to which they responded, the sex ratios of beetles responding to different blends of enantiomers in the field did not differ significantly. In a second experiment, male female pairs were sampled in the field, females were assayed for preference in a laboratory olfactometer, and male enantiomer production was measured in the laboratory. There was a significant correlation between female preference and male blend production. Pheromone production and response were not correlated with body size, nor was body size correlated in male-female pairs.

Odour stimuli affecting autumn migration of Rhopalosiphum padi (L.) (Hemipter: ornoptera)

Summary R. padi gynoparae settling in the canopy of the winter host, Prunus padus, tended to form aggregations. Differences in the degree of exposure to wind, sun, etc., did not satisfactorily explain the aggregated pattern observed. In laboratory experiments, aphids did not distinguish between leaves taken from nearby aggregations and leaves taken far away from aggregations. The results of laboratory olfactometer tests and field trapping studies indicate that R. padi gynoparae produce an aggregation pheromone. Thus the aggregated settling pattern of gynoparae of R. padi can best be explained as a response to an aggregation pheromone.

Evidence of an aggregation pheromone in the flea beetle,Phyllotreta Cruciferae (Goeze) (Coleoptera: Chrysomelidae)

Laboratory olfactometer bioassays and field trapping experiments showed that the flea beetle,Phyllotreta cruciferae (Goeze), was highly attracted by oilseed rape(Brassica napus L.) when flea beetles were on the plant. This attraction was mediated by a flea beetle-produced aggregation pheromone based upon: (1) Oilseed rape damaged mechanically, or byP. cruciferae, or by diamondback moth,Plutella xylostella (L.), did not attractP. cruciferae. (2) Contact with the plants or feeding was required for the production of aggregation pheromone because oilseed rape alone was not attractive when separated from flea beetles by a screen. (3) Equal numbers of males and females were attracted.

Identification and Attractancy of Bacteria Associated with Dacus dorsalis (Diptera: Tephritidae)

Bacteria isolated from the crop and stomach of laboratory-reared and wild oriental fruit flies, Dacus dorsalis Hendel (Diptera: Tephritidae), were identified and tested for attractancy to adult flies in a laboratory olfactometer. Bacteria were identified primarily as belonging to the family Enterobacteriaceae and included Enterobacter cloacae, E. agglomerans, Klebsiella oxytoca, Citrobacter freundii , and Kluyvera sp. Bacteria isolated from laboratory flies but found in wild flies included Providencia rettgeri, P. stuartii , and Serratia and Cedecea spp. Attractancy of flies to samples of bacteria cultures, both broth-free (washed) and in broth (unwashed), indicated a relatively low response of flies to these substrates compared with a known attractant, PIB-7 (protein hydrolysate). However, when washed bacteria were tested in the presence or absence of PIB-7 as a treatment, there was a significantly higher response of the flies to the washed bacteria when PIB-7 was absent. Washed bacteria also attracted significantly more flies than water or saline controls. When bacteria were tested as broth cultures (unwashed), they were not significantly different from the broth media in which they were grown. In washed and unwashed bacteria experiments, females showed a greater response than males when treatments were combined for analysis, whereas there were no apparent differences in response among flies of different ages to the combined treatments. Differences in response by sex to the individual treatments revealed significantly greater attraction of females to C. freundii as washed bacteria and to E. cloacae and K. pneumoniae as unwashed bacteria.