Oviposition aggregation pheromone in the Simulium damnosum complex

Abstract. Communal oviposition by the Simulium damnosum complex of Afrotropical blackflies (Diptera: Simuliidae) was investigated under controlled laboratory conditions, using wild-caught flies in Sierra Leone. Volatile compounds emitted by Simulium eggs were trapped using a closed collection system, and their attractiveness to gravid flies was tested in a two-choice behavioural bioassay. Significantly more female blackflies oviposited on substrates baited with freshly laid eggs (100% chose the baited substrate), or with the volatiles collected from freshly laid eggs (85% chose the baited substrate), in preference to the relevant control substrates. Substrates baited with volatiles from 12-h-old eggs were not significantly more attractive than controls (only 31% chose the baited substrates; P = 0.33). Gas chromatographic analysis of the egg volatiles consistently showed two peaks emanating from fresh eggs, but significantly lower amounts from 12-h-old eggs ( P <0.05). A novel system for collecting the volatiles from this and other blackfly species, as they laid eggs on a substrate in flowing water, is described. Volatiles collected using this method showed identical gas chromatographic profiles to those of fresh eggs alone, indicating that the flies themselves produced no other volatile chemical signals during oviposition. Evidently communal oviposition by S. damnosum s.l . was mediated by a pheromone emanating from fresh eggs. The role of pheromone-mediated egg aggregation in blackfly ecology is discussed, and its possible manipulation is considered.     

Volatiles released from foliar extract of host plant enhance landing rates of gravid Polygonia c‐album females,but do not stimulate oviposition

The role of olfactory cues for host search is much less investigated in day‐active butterflies than in their relatives, the nocturnal moths. The goal of this study was to investigate whether host‐plant volatiles from foliar extracts of hop, Humulus lupulus L. (Cannabaceae), evoke electroantennographic (EAG) responses, increase landing rates, and stimulate egg‐laying behavior of gravid Polygonia c‐album L. (Lepidoptera: Nymphalidae) females. Eighty‐nine volatile compounds were detected in a non‐concentrated methanol extract of hop by gas chromatography–mass spectrometry, 11 of which elicited an EAG response. Concentration of the crude extract significantly reduced landing rates on artificial leaves treated with the sample due to loss of volatile compounds, but after landing the oviposition response of gravid females was not affected. A mixture of eight commercially available EAG‐active volatiles increased the landing rate of gravid females to their source but did not act as oviposition stimulants. Dividing the volatile compounds into two groups – consisting of (1) hexanal, (E)‐2‐hexenal, octanal, nonanal, and decanal, and (2) sulcatone, humulene, and benzyl alcohol – obliterated effectiveness, revealing synergism between compounds. Although volatiles did not stimulate oviposition, they significantly contributed to the distribution of eggs by increasing the landing rates on treated artificial leaves.     

Oviposition by a moth suppresses constitutive and herbivore-induced plant volatiles in maize

Plant volatiles function as important signals for herbivores, parasitoids, predators, and neighboring plants. Herbivore attack can dramatically increase plant volatile emissions in many species. However, plants do not only react to herbivore-inflicted damage, but also already start adjusting their metabolism upon egg deposition by insects. Several studies have found evidence that egg deposition itself can induce the release of volatiles, but little is known about the effects of oviposition on the volatiles released in response to subsequent herbivory. To study this we measured the effect of oviposition by Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) moths on constitutive and herbivore-induced volatiles in maize (Zea mays L.). Results demonstrate that egg deposition reduces the constitutive emission of volatiles and suppresses the typical burst of inducible volatiles following mechanical damage and application of caterpillar regurgitant, a treatment that mimics herbivory. We discuss the possible mechanisms responsible for reducing the plant’s signaling capacity triggered by S. frugiperda oviposition and how suppression of volatile organic compounds can influence the interaction between the plant, the herbivore, and other organisms in its environment. Future studies should consider oviposition as a potential modulator of plant responses to insect herbivores.     

枸杞红瘿蚊对寄主植物挥发物的电生理和行为反应

植物挥发物是植食性昆虫定位寄主的重要信息物质。枸杞红瘿蚊是宁夏枸杞的主要成灾害虫,野外发现其雌虫对枸杞幼嫩花蕾具有更强的产卵趋性。为明确枸杞红瘿蚊对枸杞不同阶段花蕾挥发物的选择差异性,解析吸引其选择产卵的关键信息化学物质,采用顶空固相微萃取法和气相色谱-质谱联用技术(GC-MS),系统研究枸杞幼嫩花蕾和成熟花蕾挥发物的成分差异,选择幼嫩花蕾挥发物中的特有成分及其与成熟花蕾挥发物共有成分共8种作为候选挥发物;通过气相色谱-触角电位联用仪(GC-EAD)和Y型嗅觉仪,测定枸杞红瘿蚊对上述挥发物的电生理和行为反应,筛选关键活性挥发物。结果显示: 枸杞幼嫩花蕾和成熟花蕾挥发物的种类和释放量存在明显差异;8种化合物能激发枸杞红瘿蚊产生持续触角电生理反应,其中,有5种[3-蒈烯、莰烯、萜品油烯、d-柠檬烯和(+)-α-蒎烯]能刺激枸杞红瘿蚊产生显著趋向或躲避行为。利用枸杞挥发物设计枸杞红瘿蚊引诱剂或忌避剂,可为田间安全防控红瘿蚊提供新的途径。     

Fecal volatile components elicit aggregation in the oriental migratory locust,Locusta migratoria manilensis (Orthoptera: Acrididae)

Abstract The aggregation components from fecal volatiles of the oriental migratory locust, Locusta migratoria manilensis were identified with gas chromatographic/electroantennographic detector (GC‐EAD), GC‐MS (mass spectrometry) analyses and behavioral bioassays. Both last instar nymphs and adults of the oriental migratory locust have similar aggregation pheromones in their volatiles. A total of 11 electrophysiologically active compounds, namely, hexanal, cyclohexanol, heptanal, phenol, 2,5‐dimethyl‐pyrazine, benzyl alcohol, benzaldehyde, guaiacol, nonanal, 2,6,6‐trimethyl‐2‐cyclohexene‐1,4‐dione and decyl aldehyde were identified in the fecal volatiles of 2‐day‐old immature adult male locusts. Only hexanal, nonanal, benzaldehyde, cyclohexanol and 2,5‐dimethyl‐pyrazine elicited significant aggregation responses in immature 2‐day‐old adult males. However, adult males had significantly lower behavioral responses to synthetics of five single compounds than the blend of cyclohexanol, 2,5‐dimethyl‐pyrazine, benzaldehyde, nonanal, hexanal in ratios of 100: 100: 2: 60: 30 in the range of 30–60 μg/mL. We propose that it is the blend of these five compounds that plays a key role in eliciting and sustaining aggregation in gregarious oriental migratory locusts. These results also showed that the aggregation pheromones of the oriental migratory locust are significantly different from those found in the desert locust.     

Choosy egg parasitoids: Specificity of oviposition-induced pine volatiles exploited by an egg parasitoid of pine sawflies

Generalist parasitoids are well‐known to be able to cope with the high genotypic and phenotypic plasticity of plant volatiles by learning odours during their host encounters. In contrast, specialised parasitoids often respond innately to host‐specific cues. Previous studies have shown that females of the specialised egg parasitoid Chrysonotomyia ruforum Krausse (Hymenoptera: Eulophidae) are attracted to volatiles from Pinus sylvestris L. induced by the egg deposition of its host Diprion pini L. (Hymenoptera: Diprionidae), when they have previously experienced pine twigs with host eggs. In this study we investigated by olfactometer bioassays how specifically C. ruforum responded to oviposition‐induced plant volatiles. Furthermore, we studied whether parasitoids show an innate response to oviposition‐induced pine volatiles. Naïve parasitoids were not attracted to oviposition‐induced pine volatiles. The attractiveness of volatiles from pines carrying eggs was shown to be specific for the pine and herbivore species, respectively (species specificity). We also tested whether not only oviposition, but also larval feeding, induces attractive volatiles (developmental stage specificity). The feeding of D. pini larvae did not induce the emission of P. sylvestris volatiles attractive to the egg parasitoid. Our results show that a specialist egg parasitoid does not innately show a positive response to oviposition‐induced plant volatiles, but needs to learn them. Furthermore, the results show that C. ruforum as a specialist does not learn a wide range of volatiles as some generalists do, but instead learns only a very specific oviposition‐induced plant volatile pattern, i.e., a pattern induced by the most preferred host species laying eggs on the most preferred food plant.     

Pheromones in relation to aggregation and reproduction in desert locusts

Abstract. Desert locusts, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae), exhibit a population density-dependent phase polymorphism which includes the gradual change of many morphological, physiological and behavioural characteristics. Many volatiles associated with desert locusts have been identified recently and it is assumed that they are involved in pheromonal control of behaviour and development of locusts. Ovipositing females deposit with their egg pods several volatiles that appear to be attractive to other females resulting – possibly in combination with environmental factors – in an aggregated oviposition. Mature males release several volatiles, among them phenylacetonitrile, which are reported to accelerate sexual maturation in young males. Also, aggregation pheromone systems for hoppers and adults have been described. However, recent studies and publications shed a new light on the postulated effects of some of these volatiles. Gregarious behaviour can undoubtedly be induced by mechanical stimuli. Furthermore, the main component of the adult aggregation pheromone system, phenylacetonitrile, is found to be a repellent obviously not involved in aggregation. Comprehensive studies have demonstrated that phenylacetonitrile is used by mature gregarious males as a courtship inhibition pheromone to enhance mate guarding. Recent progress, contradictory results and perspectives in desert locust pheromone research related to reproduction are summarized and discussed in this paper.     

Plant volatiles induced by herbivore egg deposition affect insects of different trophic levels

Plants release volatiles induced by herbivore feeding that may affect the diversity and composition of plant-associated arthropod communities. However, the specificity and role of plant volatiles induced during the early phase of attack, i.e. egg deposition by herbivorous insects, and their consequences on insects of different trophic levels remain poorly explored. In olfactometer and wind tunnel set-ups, we investigated behavioural responses of a specialist cabbage butterfly (Pieris brassicae) and two of its parasitic wasps (Trichogramma brassicae and Cotesia glomerata) to volatiles of a wild crucifer (Brassica nigra) induced by oviposition of the specialist butterfly and an additional generalist moth (Mamestra brassicae). Gravid butterflies were repelled by volatiles from plants induced by cabbage white butterfly eggs, probably as a means of avoiding competition, whereas both parasitic wasp species were attracted. In contrast, volatiles from plants induced by eggs of the generalist moth did neither repel nor attract any of the tested community members. Analysis of the plant's volatile metabolomic profile by gas chromatography-mass spectrometry and the structure of the plant-egg interface by scanning electron microscopy confirmed that the plant responds differently to egg deposition by the two lepidopteran species. Our findings imply that prior to actual feeding damage, egg deposition can induce specific plant responses that significantly influence various members of higher trophic levels.     

Identification of oviposition attractants for the sandfly Lutzomyia longipalpis (Diptera: Psychodidae) in volatiles of faeces from vertebrates

Abstract. Extracts of volatiles from rabbit and chicken faeces preferentially attracted gravid sandflies, Lutzomyia longipalpis (Lutz and Neiva), in an oviposition bioassay. In electrophysiology experiments, the same extracts selectively stimulated two olfactory cells while inhibiting another in ascoid sensilla on the antennae of these flies. Analysis of faeces volatiles by gas chromatography linked to ascoid sensillum recording revealed two early eluting electrophysiologically active components of rabbit faeces. These active compounds were identified in both rabbit and chicken faeces volatile extracts by gas chromatography -mass spectrometry as hexanal and 2-methyl-2-butanol. Hexanal stimulated one cell type and inhibited another, whereas 2-methyl-2-butanol stimulated a third cell type. A 1:l mixture of synthetic hexanal and 2-methyl-2-butanol elicited the same targeted oviposition response from gravid females on the treatment septum of the bioassay as did the total volatile extract of rabbit or chicken faeces.
The monoterpenes α(+)-pinene (plus some optical and positional isomers) and a-terpinene activated a separate cell type, whereas benzaldehyde stimulated the same receptor as hexanal, but with a higher threshold. Furthermore, an olfactory cell selectively tuned to the perception of the male sex pheromone of this species was also found in the ascoid sensillum.     

Volatiles induced by the larvae of the Asian corn borer (Ostrinia furnacalis) in maize plants affect behavior of conspecific larvae and female adults

Abstract  Effects of maize ( Zea mays L.) volatiles induced by larvae of the Asian corn borer, Ostrinia furnacalis (Guenée), on the orientation behaviors of Asian corn borer larvae and oviposition of the females were investigated. Nineteen volatile chemicals, with terpenes being the major components, were identified from maize plants attacked by third instar Asian corn borer larvae. Coupled gas chromatographic-electroantennographic detection (GC-EAD) analyses revealed some electroantennographic differences between female and male Asian corn borer antennae in response to larvae-induced maize volatiles; female responded to ( E )-2-hexenal, nonanal, ( Z )-3-hexen-1-ol and three unknown compounds while the male only responded to ( E )-2-hexenal, nonanal and one unknown compound. In laboratory orientation bioassays, Asian corn borer neonate larvae were attracted to extracts collected from Asian corn borer-damaged plants as well as to synthetic farnesene, but were repelled by ( Z )-3-hexen-1-ol. In laboratory oviposition bioassays, gravid females laid fewer eggs on plants damaged by larvae than on mechanically damaged plants or undamaged plants. Adult Asian corn borer females deposited fewer eggs on wax paper treated with ( E )-2-hexenal or ( Z )-3-hexen-1-ol than on wax paper treated with hexane (control). The results suggest that Asian corn borer can affect the behaviors of conspecific larvae and adults by changing host plant volatiles.     

Response of Brontispa longissima to coconut palm (Cocos nucifera) leaf volatiles

Brontispa longissima (Gestro) (Coleoptera: Hispidae) is a new invasive pest in China that has caused severe economic damage to palm trees (Arecaceae, Palmae). The response of this beetle to coconut palm (Cocos nucifera) leaf volatiles is investigated in laboratory bioassays. Both sexes are attracted to a mixture of β‐myrcene, (?)‐limonene and E‐2‐hexen‐1‐ol (1 : 6 : 1), which are key components of coconut palm leaf volatiles. A blend of β‐myrcene and (?)‐limonene (0.7 : 1–1 : 0.7) in low amounts (100 ng) elicits aggregation and oviposition in females. Chemical analyses of food‐deprived, gravid female B. longissima show high concentrations of β‐myrcene and (?)‐limonene in their accessory glands, suggesting that female beetles sequester both compounds and release them during oviposition.     

Analysis of volatiles from black pine (Pinus nigra): significance of wounding and egg deposition by a herbivorous sawfly

The composition of headspace volatiles of black pine (Pinus nigra) was analysed by coupled gas chromatography-mass spectrometry (GC-MS). It has been shown in a previous study that egg deposition of the sawfly Diprion pini on P. sylvestris induces a quantitative change of the pine volatile blend . Chrysonotomyia ruforum, an egg parasitoid of D. pini, is known to be attracted by volatiles from egg-carrying P. sylvestris, but not by odour from egg-laden P. nigra. Therefore, the present study focused on the question whether also P. nigra as another host plant of this sawfly responds to egg deposition by change of its volatile blend. The headspace of untreated, egg-carrying, and artificially wounded P. nigra twigs were compared. The artificial damage inflicted to the twigs mimicked the damage by the sawfly female prior to egg deposition. Thirty five mainly terpenoid compounds that were identified in more than 50% of the egg-carrying P. nigra twigs could also be detected in the headspace of untreated and artificially wounded twigs. Quantitative differences of the blends of volatiles from differently treated P. nigra twigs were compared by multivariate data analyses. PLS-DA (projection to latent structures-discriminant analysis) revealed that blends of volatiles from differently treated P. nigra differed significantly. When comparing volatiles from egg-carrying and artificially wounded P. nigra with respective P. sylvestris samples, qualitative and quantitative differences were detected. The differences in volatile composition of P. nigra and P. sylvestris are discussed with special respect to the egg parasitoid's response to odours of egg-carrying pine twigs.     

Pine volatiles mediate host selection for oviposition by Thaumetopoea pityocampa (Lep., Notodontidae)

The oviposition behaviour and host selection by females of the pine processionary moth, Thaumetopoea pityocampa, was studied under two conditions: in a field insectary and in a pine stand. An oviposition choice test was conducted in an insectary cage, using artificial Christmas trees (ACTs) baited with extracts from four pine species: Pinus pinea, Pinus pinaster, Pinus halepensis and Pinus brutia, plus a control. Females oviposited significantly more egg batches on the ACT baited with a P. brutia extract, while no oviposition occurred on the control ACT. In a large P. pinea stand, two groups of randomly selected trees were marked and baited respectively with an extract of P. brutia, which was the preferred species under insectary conditions and with a solvent, to act as control. Results showed that oviposition in the field followed an aggregated pattern, fitting a negative binomial distribution and that trees baited with P. brutia extracts, received a significantly larger number of egg‐batches than control trees. In parallel, the volatiles emitted by all pine extracts tested where analysed by gas chromatography and mass spectrometry (GC‐MS), coupled to a time‐of‐flight (TOF) mass analyser after solid phase microextraction (SPME), resulting in the identification of 26 compounds. Comparative chromatograms showed qualitative differences among the pine species used, some compounds being present in one of them only. Findings demonstrate for the first time that: (i) T. pityocampa females discriminate among bouquets extracted from different host pine species and exhibit oviposition preferences; and (ii) olfactory cues play an important role in mediating the selection process.     

Swarming mechanisms in the yellow fever mosquito: aggregation pheromones are involved in the mating behavior of Aedes aegypti

Mosquitoes of various species mate in swarms comprised of tens of thousands of flying males. In this study, we examined Aedes aegypti swarming behavior and identified associated chemical cues. Novel evidence is provided that Ae. aegypti females aggregate by means of olfactory cues, such as aggregation pheromones. Isolation of Ae. aegypti aggregation pheromones was achieved by aeration of confined mosquitoes and collection of associated volatiles by glass filters. The collected volatiles were identified through gas chromatography mass spectrometry (GCMS). Three aggregation pheromones were collected and identified as 2,6,6‐trimethylcyclohex‐2‐ene‐1,4‐dione (ketoisophorone) (CAS# 1125–21–9, t_R = 18.75), 2,2,6‐trimethylcyclohexane‐1,4‐dione (the saturated analog of ketoisophorone) (CAS# 20547–99–3, t_R = 20.05), and 1‐(4‐ethylphenyl) ethanone (CAS# 937–30–4, t_R = 24.22). Our biological studies revealed that the identified compounds stimulated mosquito behavior under laboratory conditions. The mechanism of mosquito swarm formation is discussed in light of our behavioral study findings. A preliminary field trial demonstrated the potential application of the isolated aggregation pheromones in controlling Ae. aegypti.     

Olfactory response of Anagrus,nigriventrls (HYM.: Mymaridae): Effects of host plant chemical cues mediated by rearing and oviposition experience

The egg parasitoid Anagrus nigriventris Girault is an important natural enemy of the beet leafhopper, Circulifer tenellus (Baker) which has a broad host range that includes cultivated sugar beets and the weed, Russian thistle. When parasitoids were reared on leafhopper eggs deposited in sugar beets, females were attracted to sugar beet volatiles and preferred them over a blank control and over Russian thistle volatiles in Y- tube olfactometer tests. No preference was detected for either plant by female wasps that were reared on Russian thistle. Wasps reared on Russian thistle and allowed an oviposition experience on sugar beet showed a strong attraction to sugar beet volatiles; however, wasps reared on sugar beets and allowed oviposition experience on Russian thistle demonstrated no preference between the two plants. The implications of parasitoid response towards plant volatiles and their importance in biological control are discussed.     

Volatiles from apple (Malus domestica) eliciting antennal responses in female codling moth Cydia pomonella (L.) (Lepidoptera: Tortricidae): effect of plant injury and sampling technique

The antennal responses of codling moth females, Cydia pomonella, to volatiles from apple branches with green fruits were recorded by electroantennography coupled to gas chromatography. The antennae strongly responded to 4,8-dimethyl-1,3(E),7-nonatriene, linalool, beta-caryophyllene, (E)-beta-farnesene, germacrene D, (Z,E)-alpha-farnesene, (E,E)-alpha-farnesene and methyl salicylate. These compounds were all present in volatile collections on Porapak Q from both living and cut branches. Analysis by the solid phase microextraction technique (SPME) showed that the emission of some electrophysiologically active compounds increased after branches had been cut, especially 4,8-dimethyl-1,3(E),7-nonatriene, linalool and (E,E)-alpha-farnesene. The identification of apple volatiles eliciting antennal responses is the first step towards the identification of compounds mediating host-finding and oviposition in codling moth females.     

The significance of background odour for an egg parasitoid to detect plants with host eggs

Scots pine has been shown to produce a volatile bouquet that attracts egg parasitoids in response to oviposition of the herbivorous sawfly Diprion pini. Previous analyses of headspace volatiles of oviposition-induced pine twigs revealed only quantitative changes; in particular, the sesquiterpene (E)-beta-farnesene was emitted in significantly higher quantities by oviposition-induced pine. Here we investigated whether (E)-beta-farnesene attracted the egg parasitoid Chrysonotomyia ruforum. We tested the behavioural response of C. ruforum females to different concentrations of (E)-beta-farnesene. Egg parasitoids did not respond to this sesquiterpene at either concentration tested. However, they did respond significantly to (E)-beta-farnesene when this compound was offered in combination with the volatile blend emitted from pine twigs without eggs. This response was dependent on the applied concentration of (E)-beta-farnesene. Further bioassays with other components [(E)-beta-caryophyllene, delta-cadinene] of the odour blend of pine were conducted in combination with the volatile blend from egg-free pine as background odour. None of the compounds tested against the background of odour from an egg-free pine twig were attractive to the egg parasitoid. These results suggest that the egg parasitoids responded specifically to (E)-beta-farnesene, but only when this compound was experienced in the 'right' context, i.e. when contrasted with a background odour of non-oviposition-induced pine volatiles.     

Induction of plant responses to oviposition and feeding by herbivorous arthropods: a comparison

Plants may respond both to feeding and oviposition by herbivorous insects. While responses of plants to feeding damage by herbivores have been studied intensively during the past decades, only a few, but growing number of studies consider the reactions of plants towards egg deposition by herbivorous insects. Plants showing defensive response to oviposition by herbivores do not `wait' until being damaged by feeding, but may instead react towards one of the initial steps of herbivore attack, the egg deposition. Direct plant defensive responses to feeding act directly against the feeding stages of the herbivores. However, a plant may also show direct defensive responses to egg deposition by (a) formation of neoplasms, (b) formation of necrotic tissue (= hypersensitive response), and (c) production of oviposition deterrents. All these plant reactions have directly negative effects on the eggs, hatching larvae, or on the ovipositing females. Indirect plant defensive responses to feeding result in the emission of volatiles (= synomones) that attract predators or parasitoids of the feeding stages. A few recent studies have shown that plants are able to emit volatiles also in response to egg deposition and that these volatiles attract egg parasitoids. Studies on the mechanisms of induction of synomones by egg deposition show several parallels to the mechanisms of induction of plant responses by feeding damage. When considering induced plant defence against herbivores from an evolutionary point of view, the question arises whether herbivores evolved the ability to circumvent or even to exploit the plant's defensive responses. The reactions of herbivores to oviposition induced plant responses are compared with their reactions to feeding induced plant responses.     

Pea plant volatiles guide host location behaviour in the pea moth

Identification of plant volatiles that attract mated insect females for oviposition can provide important information about plant–insect relationships that can be used to develop pest control strategies involving manipulation of the female host search. Our study represents a first step towards identifying volatiles that affect the host location behaviour of the pea moth Cydia nigricana. The behaviours of virgin and mated males and females were analysed in cage experiments testing a two-choice situation at close range and in wind tunnel experiments evaluating upwind orientation over a distance. In both experimental setups, flowering pea plants constituted the most attractive phenological stage for mated females, with 58 % landing on such plants in the wind tunnel. Testing headspace extracts of different phenological stages of pea and of detached pea buds and flowers in the wind tunnel, mated females showed the highest landing responses to volatiles during flower development (budding 42 % and flowering 56 %) and from detached buds (46 %) and flowers (66 %). Volatile compounds collected from the various phenological stages of pea were analysed by gas chromatography–mass spectrometry, and the antennal responses to these headspace collections were evaluated by gas chromatography–electroantennography. Ten antennally active compounds were identified, nine of which were present in the headspace extracts of the whole pea plants at all tested phenological stages and in detached buds and flowers. Overall, our results demonstrate a clear link between host plant phenology, the corresponding plant odour, and the behaviour of mated C. nigricana females.     

Semiochemicals from ovaries of gravid females attract ovipositing female houseflies,Musca domestica

Chemical signals originating from the ovaries of gravid females of Musca domestica (Diptera: Cyclorrhapha: Muscidae) attract ovipositing females to common egg-laying sites. Behavioral experiments indicated that females preferred to oviposit in fermented wheat bran containing ovaries from reproductively mature houseflies. Females preferred to oviposit in fermented wheat bran than wet wheat bran. This effect was additive with the attraction to housefly ovaries. Solvent extracts from housefly ovaries were attractive to gravid females. Extracts obtained with hexane were most attractive to gravid females for egg laying, and extracts obtained with ethyl acetate attracted more egg laying than extracts obtained by dichloromethane. Gas chromatography (GC) and gas chromatography coupled with mass spectrometry (GC-MS) analysis showed that tricosane and (Z)-9-tricosene were the main components of the hexane extracts. Both tricosane and (Z)-9-tricosene were shown to elicit dose-dependent aggregation of gravid females in oviposition bioassays, but high doses of either chemical were not attractive.