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Oviposition in Spodoptera littoralis was strongly deterred by a mixture of six compounds, benzaldehyde and the five terpenes carvacrol, eugenol, nerolidol, phytol and thymol, identified from conspecific larval frass. If one of the compounds was excluded from the mixture the deterrent effect was lost. An electroantennogram-screening was performed on 15 compounds identified from the larval frass. Of the behaviourally active compounds, dose-response relationships were obtained for benzaldehyde, eugenol and nerolidol. Seven types of receptor cells specifically tuned to compounds from the larval frass were identified by single-sensillum recordings from olfactory sensilla on the female antenna. The most abundant of these was a receptor cell type responding equally well to the three aromatic terpenes carvacrol, eugenol and thymol. Receptor cells responding to only a single terpene were found for carvacrol, eugenol, nerolidol and phytol. Receptor cells responding to other frass compounds, green leaf odours and sex pheromone components were also found. No receptor cell responding to benzaldehyde was identified.

A major aim of chemical ecology is to gain deeper insight into how organismic responses to the abiotic and biotic environment are regulated by naturally produced chemicals. Chemical ecologists pursue this aim by combining chemical, molecular, and ecological expertise. While many ecological studies focus on the impact of the plethora of species on community or ecosystem functions, numerous chemoecological studies aim to elucidate the ecological relevance of a comparable bounty of natural products, their biosynthesis, transfer and metabolism as well as the organismic responses to them (Hartmann 2007). Awareness of the parallels between studies of biodiversity and chemodiversity may promote finding answers to our proximate (how) and ultimate (why) questions on the chemical mediation of organismic responses to environmental stimuli. When comparing biodiversity studies and chemoecological studies with respect to: (i) the functions of species and of natural products; (ii) the dynamics by which a community of species is established and by which a blend of chemicals is biosynthesized; and (iii) the quantification of biodiversity and chemodiversity, some informative parallels may be drawn

Plant-insect interactions are not just influenced by interactions between plants and the actively feeding stages, but also by the close relationships between plants and insect eggs. Here, we review both effects of plants on insect eggs and, vice versa, effects of eggs on plants. We consider the influence of plants on the production of insect eggs and address the role of phytochemicals for the biosynthesis and release of insect sex pheromones, as well as for insect fecundity. Effects of plants on insect oviposition by contact and olfactory plant cues are summarised. In addition, we consider how the leaf boundary layer influences both insect egg deposition behaviour and development of the embryo inside the egg. The effects of eggs on plants involve egg-induced changes of photosynthetic activity and of the plant's secondary metabolism. Except for gall-inducing insects, egg-induced changes of phytochemistry were so far found to be detrimental to the eggs. Egg deposition can induce hypersensitive-like plant response, formation of neoplasms or production of ovicidal plant substances; these plant responses directly harm the eggs. In addition, egg deposition can induce a change of the plant's odour and leaf surface chemistry which serve indirect plant defence with the help of antagonists of the insect eggs. These egg-induced changes lead to attraction of egg parasitoids and their arrestance on a leaf, respectively. Finally, we summarise knowledge of the elicitors of egg-induced plant changes and address egg-induced effects on the plant's transcriptional pattern.

Besides the known sarmentogenin 3-O-β-D-allopyranoside (1) and digitoxigenin-3-O-[β-D-xylopyranosyl-(1→4)-2′, 3′-di-O-acetyl-β-D-allopyranoside] (4), four new cardiac glycosides (2, 3, 5 and6) have been isolated from the defensive glands of adults ofChrysolina fuliginosa. The structures of the new compounds were determined by1H NMR at 600 MHz and FABMS. Compounds1–6, present in the adults ofC. fuliginosa, have also been identified in the eggs.

Precise and deep comprehension of plant responses to herbivorous arthropods requires detailed knowledge of how a plant "notices" the attack. Herbivore attack is not restricted to plant wounding by feeding, but instead different phases of attack that elicit a plant response need to be distinguished: touch, oviposition and feeding. Touch, secretions released with eggs and regurgitate delivered during feeding may act in concert as elicitors of plant defence. Here, we discuss the current knowledge of what a plant "notices" during the different phases of herbivore attack and how it responds at the molecular, physiological and ecological level. Understanding the mechanisms of plant responses to the different phases of herbivore attack will be a key challenge in unravelling the complex communication pathways between plants and herbivores.

During mating in many butterfly species, males transfer spermatophores that contain anti-aphrodisiacs to females that repel conspecific males. For example, males of the large cabbage white, Pieris brassicae (Lepidoptera: Pieridae), transfer the anti-aphrodisiac, benzyl cyanide (BC) to females. Accessory reproductive gland (ARG) secretion of a mated female P. brassicae that is deposited with an egg clutch contains traces of BC, inducing Brussels sprouts plants (Brassica oleracea var. gemmifera) to arrest certain Trichogramma egg parasitoids. Here, we assessed whether deposition of one egg at a time by the closely related small cabbage white, Pieris rapae, induced B. oleracea var. gemmifera to arrest Trichogramma wasps, and whether this plant synomone is triggered by substances originating from male P. rapae seminal fluid. We showed that plants induced by singly laid eggs of P. rapae arrest T. brassicae wasps three days after butterfly egg deposition. Elicitor activity was present in ARG secretion of mated female butterflies, whereas the secretion of virgin females was inactive. Pieris rapae used a mixture of methyl salicylate (MeSA) and indole as an anti-aphrodisiac. We detected traces of both anti-aphrodisiacal compounds in the ARG secretion of mated female P. rapae, whereas indole was lacking in the secretion of virgin female P. rapae. When applied onto the leaf, indole induced changes in the foliar chemistry that arrested T. brassicae wasps. This study shows that compounds of male seminal fluid incur possible fitness costs for Pieris butterflies by indirectly promoting egg parasitoid attack.

Female parasitic wasps seek hosts for their offspring often in a dynamic environment. Foraging egg parasitoids rely on a variety of chemical cues originating from the adult host, host products, or the host plant rather than from the attacked host stage--the insect egg itself. Besides pupae, insect eggs are the most inconspicuous host stage attacked by parasitic wasps. To overcome the problem of low detectability of host eggs, egg parasitoids have evolved several strategies such as exploiting long-range kairomones of the adult hosts, for example, host aggregation and sex pheromones, plant synomones induced by egg deposition or host feeding, or short-range contact cues derived from the adult host or the host plant. Moreover, egg parasitoids have evolved the ability to use chemical espionage in combination with hitchhiking on the adult host (phoresy) to compensate their limited flight capability and to gain access to freshly laid host eggs. Here, we provide a comprehensive overview on the variety of host-foraging strategies of egg parasitoids exploiting chemical signals. Furthermore, the use of such infochemicals is discussed with respect to the wasps' dietary breadth and their ability to learn. Copyright 2008, Oxford University Press.

A synthetic mixture containing 1-indanone, 2-pentanone, 2-methyl-3-pentanone, 3-mcthyl- 2-pentanone, 2-methylcyclopentanone. 1-hydroxy-propanone. acetophenone, benzaldehyde. n-nonanal, n-decanal, nerolidol, eugenol, thymol, carvacrol and phythol deters oviposition of the Egyptian cotton leaf worm, Spodoptera littoralis (Boisd.). All compounds were identified from larval frass of S. littoralis.

Eggs of leaf beetles of the tribe Galerucini, subfamily Galerucinae, contain polyketides that are unusual in insects: 1,8-dihydroxylated anthraquinones (chrysazin, chrysophanol) and anthrones (dithranol, chrysarobin) deterring predators. The host plants do not contain these compounds. In the present study, we tested the hypothesis that the beetles, but not bacterial or fungal microorganisms living as endosymbionts within the beetles, produce the anthraquinones. The tansy leaf beetle Galeruca tanaceti was used as Galerucini model organism. It was treated with antimicrobial substances to eradicate the microorganisms and inhibit the hypothesised endosymbiotic anthraquinone production. Despite treatment, female G. tanaceti laid eggs containing anthraquinones. Although broad spectrum antimicrobials were used, it cannot be excluded that the potential endosymbiotic microorganisms are resistant. Given that the hypothesised endosymbionts are transferred via the eggs from one generation to the next, bacterial or fungal DNA was expected to be present in the eggs. With the exception of Wolbachia pipientis, however, no further 16S rDNA from bacteria responsible for anthraquinone biosynthesis was detected in eggs of untreated beetles. Because Wolbachia were also found in closely related anthraquinone-free insects, we exclude these bacteria as producers of the defensive polyketides. Nor was any 18S rDNA from fungi with anthraquinone biosynthetic abilities detected. Our results indicate that anthraquinones and anthrones in eggs of Galerucini are produced by beetle enzymes and not by endosymbiotic microorganisms within the eggs.

The Palaearctic leaf beetle Chrysomela lapponica usually feeds upon willows in the northern region of its occurrence. However, in Central Europe, some populations are known that have specialised on birch. In this study, we investigated the significance of other herbivores occurring together on the same host plants as possible exploitative competitors of C. lapponica. Two populations were studied: a population from Finland specialised on the willow Salix borealis, and a population from the Czech Republic, specialised on the birch Betula pubescens. Abundances of folivorous and suctivorous insects on both host plants were recorded at both population sites. The willow leaf beetle Phratora vitellinae was the most abundant herbivorous insect at both study sites on willow. A field study was conducted to examine the effects of P. vitellinae on the performance of C. lapponica. The presence of P. vitellinae larvae on the same twig upon which C. lapponica larvae were feeding did not affect increase of body weight in C. lapponica larvae. Thus, the high resource availability of both willows and birches suggest that interspecific competition is unlikely to be a selection factor driving the evolution of host shift in C. lapponica.

SUMMARY Drosophila melanogaster (Meigen) detects and uses many volatiles for its survival. Carbon dioxide (CO2) is detected in adults by a special class of olfactory receptor neurons, expressing the gustatory receptor Gr21a. The behavioral responses to CO2 were investigated in a four-field olfactometer bioassay that is new for Drosophila. We determined (1) whether the sensitivity of this response changes with odor context, and (2) if it depends on sex and life stage. When CO2 was added to ambient air in one field and tested against ambient air in the three other fields, individually observed adults avoided CO2 (0.1-1%above ambient), but did not respond to a low rise of 0.02%. We relate this behavior to measurements of CO2 production in bananas and flies. When 0.02% CO2 was combined with the odor of apple cider vinegar in one field of the olfactometer and tested against ambient air in the three other fields, the addition of CO2 did not affect the attractiveness of apple cider vinegar alone. However, this combination of CO2 and vinegar became repellent when it was tested against vinegar at ambient CO2 concentrations in the three other fields. This `odor background effect' was female-specific, revealing a sexually dimorphic behavior. The new assay allowed us to test larvae under similar conditions and compare their behavior to that of adults. Like adults, they avoided CO2, but with lower sensitivity. Larvae lacking neurons expressing Gr21a lost their avoidance behavior to CO2, but kept their positive response to vinegar odor. Hence, Gr21a-expressing neurons mediate similar behaviors in larvae and adults.

The chemical defence of pine against herbivorous insects has been intensively studied with respect to its effects on the performance and behaviour of the herbivores as well as on the natural enemies of pine herbivores. The huge variety of terpenoid pine components play a major role in mediating numerous specific food web interactions. The constitutive terpenoid pattern can be adjusted to herbivore attack by changes induced by insect feeding or oviposition activity. Recent studies on folivorous pine sawflies have highlighted the role of induced pine responses in herbivore attack and have demonstrated the importance of analysing the variability of pine defence and its finely tuned specificity with respect to the herbivore attacker in a multitrophic context.

Scots pine (Pinus sylvestris) is known to change its terpenoid metabolism in response to egg deposition by the sawfly Diprion pini (Hymenoptera, Diprionidae). Three days after egg deposition, parts of the pine twig adjacent to the egg-laden one are induced to emit volatiles, which attract egg parasitoids. In this study, we investigated whether egg deposition by this sawfly affects pine photosynthesis. Measurements of photosynthesis were taken from untreated control twigs and from pine twigs adjacent to egg-laden ones (i.e. systemically oviposition-induced twigs) for a period of 3 d starting after egg deposition. The net photosynthetic rate of oviposition-induced pine twigs was lower than that of untreated control twigs, whereas the respiration rate of pine twigs was not affected by egg deposition. CO2 response curves of oviposition-induced twigs tended to be lower than those of controls. The potential rate of electron transport (J max) and the maximum rate of Rubisco activity (V cmax) were calculated from the data of the CO2 response curves. J max of oviposition-induced twigs was significantly lower than that of controls at day 1 after egg deposition, while the difference diminished from day 2 to day 3. A similar pattern was observed for V cmax. Light response curves of oviposition-induced twigs were significantly lower than those of untreated ones during 3 d of measurements. Stomatal conductance was slightly lowered by egg deposition. When considering photosynthetic activity as a physiological currency to measure costs of induction of plant defense, the effects of insect egg deposition on gas exchange of pine are discussed with respect to known effects of insect feeding on the photosynthesis activity of plants.

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.

To locate their hosts, parasitic wasps can 'eavesdrop' on the intraspecific chemical communications of their insect hosts. Here we describe an example in which the information exploited by the parasitic wasp Trichogramma brassicae is a butterfly anti-aphrodisiac that is passed from male to female Pieris brassicae butterflies during mating, to render them less attractive to conspecific males. When the tiny wasp detects the odour of a mated female butterfly, it rides on her (Fig. 1) to her egg-laying sites and then parasitizes the freshly laid eggs. If this fascinating strategy is widespread in nature, it could severely constrain the evolution of sexual communication between hosts.

The occurrence and distribution of tropane and biogenetically related pyrrolidine alkaloids in 18 Merremia species of paleo-, neo-, and pantropical occurrence have been studied. The extensive GC-MS study included members of almost all sections of the genus and has been carried out with epigeal vegetative parts as well as with roots. It comprises altogether 74 tropanes and 13 pyrrolidines including nicotine. Along with datumetine known already from a solanaceous species, the study led to the isolation (from M. dissecta and M. guerichii, respectively) and structure elucidation (spectral data) of four novel 3alpha-acyloxytropanes, merresectines A-D: 3alpha-(4-methoxybenzoyloxy)nortropane (A), 3alpha-kurameroyloxytropane (B), 3alpha-nervogenoyloxytropane (C), 3alpha-[4-(beta-D-glucopyranosyloxy)-3-methoxy-5-(3-methyl-2-butenyl)benzoyloxy]tropane (beta-d-glucoside of D). Moreover, the novel 3alpha,6beta-di-(4-methoxybenzoyloxy)tropane (merredissine) has been isolated from M. dissecta and structurally elucidated. In addition the structures of datumetine and merresectine A could be confirmed by synthesis. Spectral data for two known 3alpha-acyloxytropanes (merresectine E beta-D-glucoside, 4'-dihydroconsabatine) and one known 3beta-acyloxytropane (concneorine) are documented for the first time. The structures of three further merresectines (F-H) have been determined by mass spectrometry. Furthermore, the linkage (2',3- and 2',4-, respectively) of two position isomer N-methylpyrrolidinylhygrines was proven by synthesis. The results of the study contribute to the solution of infrageneric taxonomic problems. Whereas all species yield pyrrolidine alkaloids without suitably differentiating results the diverging occurrence of tropane alkaloids leads to three groups of sections: (1) taxa free of tropanes, (2) taxa with simple tropanes, and (3) taxa with merresectines in addition to simple tropanes.

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. Naive 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.

Plants can defend themselves against herbivorous insects before the larvae hatch from eggs and start feeding. One of these preventive defence strategies is to produce plant volatiles, in response to egg deposition, which attract egg parasitoids that subsequently kill the herbivore eggs. Here, we studied whether egg deposition by Pieris brassicae L. (Lepidoptera: Pieridae) induces Brussels sprouts plants to produce cues that attract or arrest Trichogramma brassicae Bezdeko (Hymenoptera: Trichogrammatidae). Olfactometer bioassays revealed that odours from plants with eggs did not attract or arrest parasitoids. However, contact bioassays showed that T. brassicae females were arrested on egg-free leaf squares excised from leaves with 72 h-old egg masses, which are highly suitable for parasitisation. We tested the hypothesis that this arresting activity is due to scales and chemicals deposited by the butterflies during oviposition and which are thus present on the leaf surface in the vicinity of the eggs. Indeed, leaf squares excised from egg-free leaves, but contaminated with butterfly deposits, arrested the wasps when the squares were tested 1 day after contamination. However, squares from egg-free leaves with 72 h-old butterfly deposits had no arresting activity. Thus, we exclude that the arresting activity of the leaf area near 72 h-old egg masses was elicited by cues from scales and other butterfly deposits. We suggest that egg deposition of P. brassicae induces a change in the leaf surface chemicals in leaves with egg masses. A systemic induction extending to an egg-free leaf neighbouring an egg-carrying leaf could not be detected. Our data suggest that a local, oviposition-induced change of leaf surface chemicals arrests T. brassicae in the vicinity of host eggs.

A comprehensive GC–MS analysis of 8 Ipomoea species belonging to the subgenus Quamoclit, section Mina revealed that the members of this taxon form combinations of two necine bases with rare necic acids resulting in unique pyrrolizidine alkaloids. The occurrence and diversity of these metabolites show remarkable variations: Some species, especially Ipomoea hederifolia and Ipomoea lobata , are able to synthesize a large number of alkaloids whereas others, especially Ipomoea coccinea and Ipomoea quamoclit , are poor synthesizers with only a few compounds. However, these metabolites are apparently chemotaxonomic markers of this infrageneric taxon in general. They represent either esters of (−)-platynecine (altogether 48 ipangulines and 4 further esters including results of a previous study) or esters of (−)-trachelanthamidine, an additional novel structural type called minalobines (altogether 21 alkaloids). Both types are characterized by section-specific rare necic acids, e.g., ipangulinic/isoipangulinic acid, phenylacetic acid. The alkaloids of Ipomoea cholulensis , I. coccinea , I. hederifolia , Ipomoea neei , and Ipomoea quamoclit were mono and diesters of platynecine. Minalobines turned out to be metabolites of I. lobata (Cerv.) Thell. (syn.: Mina lobata Cerv.) lacking ipangulines. The major alkaloid of this species, minalobine R, has been isolated and identified as 9- O -( threo -2-hydroxy-2-methyl-3-phenylacetoxy-butyryl)-(−)-trachelanthamidine on the basis of spectral data. Apparently only two of the species included in this study, Ipomoea cristulata and Ipomoea sloteri , are able to synthesize both, ipangulines as well as minalobines. Minalobine O could be isolated as a major alkaloid of I. cristulata , its structure has been established as 9- O -( erythro -2-hydroxy-2-methyl-3-tigloyloxy-butyryl)-(−)-trachelanthamidine on the basis of spectral data.

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.

Gas chromatography-mass spectrometry analyses of the headspace volatiles of Scots pine (Pinus sylvestris) induced by egg deposition of the sawfly Diprion pini were conducted. The odor blend of systemically oviposition-induced pine twigs. attractive for the eulophid egg parasitoid Chrysonotomyia ruforum, was compared to volatiles released by damaged pine twigs (control) that are not attractive for the parasitoid. The mechanical damage inflicted to the control twigs mimicked the damage by a sawfly female prior to egg deposition. The odor blend released by oviposition-induced pine twigs consisted of numerous mono- and sesquiterpenes, which all were also present in the headspace of the artificially damaged control twigs. A quantitative comparison of the volatiles from oviposition-induced twigs and controls revealed that only the amounts of (E)-beta-farnesene were significantly higher in the volatile blend of the oviposition-induced twigs. Volatiles from pine twigs treated with jasmonic acid (JA) also attract the egg parasitoid. No qualitative differences were detected when comparing the composition of the headspace of JA-treated pine twigs with the volatile blend of untreated control twigs. JA-treated pine twigs released significantly higher amounts of (E )-beta-farnesene. However, the JA treatment induced a significant increase of the amount of further terpenoid components. The release of terpenoids by pine after wounding, egg deposition, and JA treatment is discussed with special respect to (E)-beta-farnesene.

The insects that cause or transmit human and animal disease constitute a wide range of taxa sharing a similar feeding habit, but differing in most other aspects of their life histories, including oviposition. This chapter mainly deals with oviposition or larviposition behaviour within the Diptera, since the major groups that exhibit such behaviour and that constitute pests of major medical or veterinary importance are true flies. Aggregation behaviour in bloodsucking Hemiptera is discussed briefly. Bloodfeeding groups generally oviposit at sites remote from their vertebrate hosts: mosquitoes (Culicidae) and blackflies (Simuliidae) oviposit in aquatic environments, and sandflies (Psychodidae), tsetse flies (Glossinidae), bedbugs (Cimicidae) and kissing bugs (Reduviidae) oviposit in terrestrial environments. Facultative or obligatory carnivorous Diptera, where the immature stages can be saprotrophic or parasitic on the same animals on which the adult flies feed, also locate and select oviposition or larviposition sites using chemical cues. These include warble flies, bot flies (Oestridae), blowflies, screwworms (Calliphoridae) and flesh flies (Sarcophagidae). Not surprisingly, given the range of life histories of these diverse groups, the interaction of pheromones with visual cues, odours of environmental origin and the physical properties of the oviposition site, is wide-ranging in nature. Knowledge of the chemoecology of oviposition in these insects lags behind that on herbivorous and parasitic insects and attractant compounds have been identified in only a few cases. A number of plant species have evolved to mimic animal odour cues to attract carnivorous fly species as pollinators. Because of the importance of these insects as vectors of human and animal disease, interest in this field has been driven primarily by a search for chemically baited traps for monitoring and control. Odour baited oviposition traps are currently used in the surveillance of a number of important pest species. Odour baited trapping for the control of pest populations may be feasible for certain species. 5.

Chemical orientation of the European cockchafer, Melolontha melolontha L., a serious pest in agriculture and horticulture, was investigated by field tests and electrophysiological experiments using plant volatiles. In total, 16 typical plant volatiles were shown to elicit electrophysiological responses in male cockchafers. Funnel trap field bioassays revealed that green leaf alcohols (i.e. (Z)-3-hexen-1-ol, (E)-2-hexen-1-ol and 1-hexanol) attracted males, whereas the corresponding aldehydes and acetates were behaviourally inactive. Furthermore, male cockchafers were attracted by volatiles from mechanically damaged leaves of Fagus sylvatica L., Quercus robur L. and Carpinus betulus L. However, volatiles emitted by damaged leaves of F. sylvatica attracted significantly more males than those from the other host plants. Odour from intact F. sylvatica leaves was not attractive to M. melolontha males. Females were not attracted by any of the tested volatile sources. The results suggest that plant volatiles play a similar role as a sexual kairomone in mate finding of M. melolontha, as has been shown for the forest cockchafer, Melolontha hippocastani F. Nevertheless, both species show remarkable differences in their reaction to green leaf alcohols.

The exocrine glandular secretions of leaf beetle larvae of the taxon Chrysomela are well-known defensive devices used against some generalist predators. Salicylaldehyde is the major repellent component of secretions emitted by larvae of Chrysomela vigintipunctata and C. lapponica, which feed on salicin-rich Salicaceae. In this study, we examined whether salicylaldehyde is also active against the entomopathogenic fungus Metarhizium anisopliae. The germination and growth of this fungus was strongly inhibited when salicylaldehyde was applied directly onto the blastospores. The salicylaldehyde concentration of the larval secretions of the tested willow feeding Chrsysomela larvae was much higher than the one necessary to display this antifungal activity. Additionally, salicylaldehyde was shown to reduce germination and growth of M. anisopliae via the gas phase over a distance of 45 mm. Further studies on the antimicrobial activity of the salicylaldehyde-containing secretions of Chrysomela larvae revealed that they act nonspecifically against prokaryotic (Escherichia coli) and eukaryotic cells (Saccharomyces cerevisiae and Trichoplusia ni). All antimicrobial and cytotoxic effects detected proved to be due to salicylaldehyde. The larval secretions of the birch-feeding allospecies of C. lapponica, that do not contain salicylaldehyde, but mainly carboxylic acids and their esters, showed no detectable effects on bacteria or fungi and no cytotoxic effects against insect cells. The results are discussed with respect to their ecological relevance.

Larvae and adults of the mustard leaf beetle Phaedon cochleariae (Coleoptera: Chrysomelidae) possess exocrine glands with secretions which are used in defense against predators. This study addressed the question whether these defensive secretions also display antimicrobial activity. Additionally, the effects of larval and adult hemolymph and larval regurgitate toward microorganisms were examined. The larval glandular secretion showed growth-inhibitory activity against the gram-negative bacterium Escherichia coli, but no lytic effect against cell walls of the gram-positive bacterium Micrococcus luteus. Growth of the yeast Saccharomyces cerevisiae and of the entomopathogenic fungus Beauveria bassiana was also inhibited by the larval secretion. The antibacterial and antifungal activity of the larval secretion was found to be due to its main component, the iridoid monoterpene, (epi)chrysomelidial. The mechanism of its antifungal activity was examined by different bioassays and compared to the commercially available fungicide nystatin. The antifungal activity of the larval secretion is not due to a loss of intracellular potassium in treated fungal cells, while high potassium efflux from treated cells is the mode of action of common fungicides. The larval secretion exhibited direct cytotoxicity against both fungal cells and plasmatocytes isolated from the greater wax moth Galleria mellonella. In contrast to the larval secretion, the adult glandular secretion of P. cochleariae showed lytic activity against the cell walls of the gram-positive bacterium M. luteus, but no activity against the gram-negative bacterium E. coli and eukaryotic cells. Hemolymph and larval regurgitate of P. cochleariae displayed the same activity as the tested glandular secretion of adults. Copyright 1998 Academic Press.

Chrysomelid larvae of the subfamily Galerucinae, tribe Galerucini, are known to contain 1,8-dihydroxylated 9,10-anthraquinones. Since nonhydroxylated 9,10-anthraquinone is the active agent in several commercial products sold to protect seeds against birds, we suggested that the naturally occurring dihydroxylated anthraquinones of galerucine larvae may also act as protective devices against bird predation. Tits (Parus spp.) are potential predators of larvae of the tansy leaf beetle, Galeruca tanaceti, and the elm leaf beetle, Xanthogaleruca luteola. To investigate the palatability of these chrysomelid larvae to birds, we offered them with mealworms and Calliphora pupae, respectively, as controls in dual choice bioassays to eight singly kept, naive tits (five P. major and three P. ater individuals). The bioassays were limited to 5 days, during which larvae were offered daily for 2 h (X. luteola) and 3 h (G. tanaceti), respectively. Every day, the birds significantly avoided uptake of G. tanaceti and X. luteola. More than 98% of the control food was consumed daily, whereas the percentage of chrysomelid larvae totally eaten never surpassed 6.6% for G. tanaceti and 51.8% for X. luteola. In order to determine whether this avoidance was due to the anthraquinones of the chrysomelid larvae, mealworms and Calliphora pupae, respectively, were treated with these compounds in concentrations equivalent to the natural ones. Dual choice bioassays with treated and untreated prey were conducted, again for 5 days with a daily 2- or 3-h test period, respectively. The tits ate all or nearly all treated and untreated food items every day. However, during the 5-day test period the tits learnt to take up the control insects significantly earlier than the treated ones; the food containing anthraquinones was not consumed as readily as the control, which suggest aversive learning based on distastefulness. The efficiency of anthraquinones in protecting galerucine larvae against bird predation is discussed with special respect to learning behavior and factors which might delay or mask learning of avoidance.

As the immobile stage insect eggs are most vulnerable and endangered. How are they protected against enemies, microbial disease, and desiccation? In chrysomelid eggs, several toxins and feeding deterrents of completely different chemical character are known and have been reviewed a few years ago by Pasteels et al. (1988a). In addition to toxic and deterrent defensive devices, eggs may be protected from enemies by mechanical barriers, which are of high diversity in Chrysomelidae; several of them are described by Von Lengerken (1954) and Hinton (1981). A chrysomelid female may even use its own body as a mechanical barrier either by guarding deposited eggs (parental care) or by shielding eggs during the entire embryonic development (ovoviviparity). An ovipositing female may also take care of the progeny by its choice of an oviposition site, which provides hatching larvae with sufficient protection and food. In Chrysomelidae, a few studies demonstrate that egg depositions are avoided at sites, which have already been infested by conspecifics (e.g. Van Alphen & Boer, 1980). In several species of the subfamily Chrysomelinae, females are known to be deterred from oviposition by the secretions of conspecific larvae (Hilker, 1989a).

The defensive secretion ofChrysomela lapponica larvae, which is produced by nine pairs of exocrine dorsal glands, has been chemically analyzed. TheC. lapponica larvae were kept in the laboratory on leaves of either birch (Betula pendula), alder (Alnus glutinosa), or willow (Salix fragilis). Larvae developed normally on birch and willow, whereas those on alder died within a few days. GC-MS analyses of the secretion of larvae on birch and willow revealed that the composition of this secretion differs distinctly from the known ones of several otherChrysomela species feeding exclusively on Salicaceae. In the exocrine secretion of larvae on birch, 69 compounds were identified, which included the main components isobutyric acid, 2-methylbutyric acid, and esters of the two. Several of the esters have not been reported previously from nature. The alcoholic components of the esters may be hydrolysis products ofBetula glycosides. Most components of the secretion of larvae feeding on birch were also found in the secretion of larvae feeding on willow. In addition, major amounts of benzoic acid and salicylalcohol were present in the secretion of the larvae feeding on willow.C. lapponica obviously acquires salicylalcohol by hydrolysis of salicin from willow leaves. However, in contrast to otherChrysomela species,C. lapponica larvae oxidize only traces of salicylalcohol to salicylaldehyde. The repellent activity of single authentic compounds of the secretion of larvae feeding on birch and willow, respectively, was tested in laboratory bioassays with ants (Myrmica sabuleti). Biosynthetic pathways to some identified compounds are suggested and discussed under evolutionary and functional aspects.

The overwintering eggs and the larvae of the leaf beetleGaleruca tanaceti (L.) contain hydroxylated anthraquinones. In both developmental stages, l,8-dihydroxy-3-methylanthraquinone (= chrysophanol) and 1,8-di-hydroxyanthraquinone (= chrysazin) were detected by GC-MS and GC-FTIR analyses. In the eggs, chrysazin was found only in traces. Anthraquinones were also present in ovaries and hemolymph of gravid females, which were investigated in order to examine the incorporation of these substances into the eggs. Neither in acidified nor in nonacidified extracts of the host plantsTanacetum vulgare L. andAchillea millefolium L. were anthraquinones found. The activity of these anthraquinones as chemical defense substances was proved in bioassays with the antMyrmica ruginodis NYL. Further possible biological significances of anthraquinones are discussed.

To locate their hosts, parasitic wasps can 'eavesdrop' on the intraspecific chemical communications of their insect hosts1, 2, 3. Here we describe an example in which the information exploited by the parasitic wasp Trichogramma brassicae is a butterfly anti-aphrodisiac that is passed from male to female Pieris brassicae butterflies during mating, to render them less attractive to conspecific males4, 5, 6. When the tiny wasp detects the odour of a mated female butterfly, it rides on her (Fig. 1) to her egg-laying sites and then parasitizes the freshly laid eggs. If this fascinating strategy is widespread in nature, it could severely constrain the evolution of sexual communication between hosts.

The larval secretions of the Chrysomelinae (Coleoptera, Chrysomelidae) are generally considered to be chemical defense substances against predators and parasites. The experiments presented in this paper provide evidence that the range of activity of these larval secretions also extends to interactions between different conspecific developmental stages and between competing phytophagous species. Four chrysomeline species were tested: Gastrophysa viridula De Geer, Phaedon cochleariae (F.), Plagiodera versicolora (Laich.), and Phratora vitellinae (L.). In the latter species, we did not test the intraspecific effect of the natural larval secretion, but the activity of its purchasable main component, salicylaldehyde (synthetic larval secretion). In G. viridula, Ph. cochleariae, and Ph. vitellinae the (synthetic) larval secretions act as oviposition deterrents against conspecific females. An investigation of the persistence of the ovipositiondeterring activity of the larval secretion in G. viridula revealed that the deterrent effect is lost after 20 to 26 hours. In each of the four tested species the (synthetic) larval secretion deters feeding of conspecific adults. Since P. versicolora and Ph. vitellinae may occur on the same host plant (e.g. the willow Salix fragilis L.), the interspecific effect of the larval secretion between competing phytophagous species was examined in these two willow leaf beetles. The larval secretions of both species and salicylaldehyde, respectively, act as interspecific repellent and feeding deterrent against adults of the other species. Zusammenfassung Intra- und interspezifische Effekte der Larvensekrete einiger Chrysomeliden (Coleoptera) Die Sekrete der Larven der Chrysomelinae (Fam. Chrysomelidae) werden im allgemeinen als chemische Abwehrstoffe gegen Pradatoren und Parasiten betrachtet. Die hier dargestellten Untersuchungen zeigen, das die Wirkung der Larvensekrete nicht nur auf die Feindabwehr begrenztist. Das Wirkungsspektrum umfast daruber hinaus auch Interaktionen zwischen verschiedenen Entwicklungsstadien einer Art bzw. zwischen konkurrierenden phytophagen Arten. Folgende Chrysomelinenarten wurden untersucht: Gastrophysa viridula De Geer, Phaedon cochleariae (F.), Phratora vitellinae (L.) und Plagiodera versicolora (Laich.). Da das Larvensekret von Ph. vitellinae Salicylaldehyd als Hauptkomponente enthalt, wurde hier – wenn nicht anders erwahnt – die Wirkung von synthetischem Salicylaldehyd getestet. Bei G. viridula, Ph. cochleariae und Ph. vitellinae wirkt das Larvensekret bzw. die authentische synthetische Substanz als hochwirksames Eiablage-Deterrens auf konspezifische Weibchen. Die eiablagehemmende Wirkung des Larvensekretes von P. versicolora wurde nicht getestet. Eine Untersuchung der Wirkungsdauer der eiblagehemmenden Aktivitat des Larvensekretes von G. viridula ergab, das die Hemmwirkung nach 20 bis 26 Stunden nicht mehr nachweisbar ist. Bei alien oben genannten vier Arten hemmt das Larvensekret bzw. dessen authentische synthetische Substanz den Fras von Adulten derselben Art. Diese frashemmende Aktivitat ist bei G. viridula, Ph. cochleariae und Ph. vitellinae mindestens 18 Stunden wirksam. Das Larvensekret von P. verskolora zeigte bei 18-stundiger Versuchsdauer keine frashemmende Wirkung auf Adulte derselben Art; erst bei Reduktion der Versuchsdauer auf drei Stunden konnte hier eine signifikant frashemmende Wirkung nachgewiesen werden. P. verskolora und Ph. vitellinae konnen als Weidenblattkafer an derselben Wirtspflanze auftreten, Deshalb wurde auch die interspezifische Wirkung der Larvensekrete dieser beiden Chrysomelinenarten gepruft. Das Larvensekret von Ph. vitellinae sowie auch dessen authentische synthetische Substanz (Salicylaldehyd) wirkt auf adulte P. verskolora als Repellent und Frashemmstoff. Ebenso wirkt urngekehrt das Larvensekret von P. verskolora abschreckend und frashemmend auf adulte Ph. vitellinae.

The ancestral host plants of Chrysomela lapponica are Salicaceae rich in salicylic glycosides (SGs), which serve as precursors for larval chemical defensive secretions. Nevertheless, some populations have shifted to plants poor in SGs or even lacking these compounds. To study whether this shift is accompanied by adaptations to novel SG-poor host plants, we reared C. lapponica larvae from five geographical populations on host plants with high (Salix myrsinifolia) or low (S. caprea) SG content. Individuals from two populations (Finland and Kola region in Russia) associated in nature with SG-rich S. myrsinifolia showed higher survival and shorter developmental time on native host species than on foreign SG-poor S. caprea, thus demonstrating local adaptations to their ancestral SG-rich host plant. Individuals from a Belarus population associated in nature with SG-poor S. caprea showed higher survival on this species than on foreign SG-rich S. myrsinifolia, thus demonstrating local adaptation to the novel SG-poor host. On the other hand, individuals from two other populations associated in nature with SG-poor plants (Baikal and Ural region) performed equally well on both SG-rich S. myrsinifolia and SG-poor S. caprea in our rearing experiments, thus showing no local adaptation to a specific SG-host type, but rather a wide feeding niche including several Salicaceae species of different SG-type. Our results suggest that diet breadth of C. lapponica is a local phenomenon, and that adaptation strategies to novel host plants may differ between populations of a single leaf beetle species.

Scots pine (Pinus sylvestris; Pinaceae, Pinales) is known to defend against egg deposition by herbivorous sawflies by changing its terpenoid volatile blend. The oviposition-induced pine odor attracts egg parasitoids that kill the sawfly eggs. Here, we investigated whether sawfly egg deposition activates genes encoding pine terpene synthases by extracting mRNA from oviposition-induced P. sylvestris. Three new sesquiterpene synthases, PsTPS 1, PsTPS 2, and PsTPS 3, were isolated that were shown on heterologous expression in Escherichia coli to produce (E)-β-caryophyllene and α-humulene (PsTPS 1), 1(10),5-germacradiene-4-ol (PsTPS 2), and longifolene and α-longipinene (PsTPS 3) as their principal products. Quantitative RT-PCR analyses revealed that transcript levels of PsTPS 1 and PsTPS 2 were significantly higher in oviposition-induced twigs that were attractive to the parasitoids than in non-attractive, artificially damaged twigs. Thus, our results demonstrate a specific transcription response to egg deposition, distinct from that caused by artificial wounding. Transcripts of PsTPS 3 did not change in response to egg deposition. The transcript levels of PsTPS 1, PsTPS 2, and PsTPS 3 were also determined in relation to time after egg deposition, since pine odor is attractive to the parasitoid only 72 h after egg deposition. Transcription rates of PsTPS 1 and PsTPS 2 were significantly enhanced only 72 h after egg deposition, thus matching the timing of odor attractiveness, while for PsTPS 3, enhanced transcription was not detected at any time period studied after egg deposition. The ecological significance of the oviposition-induced increase of sesquiterpene synthase transcripts is discussed. Electronic supplementary material The online version of this article (doi:10.1007/s00425-008-0747-8) contains supplementary material, which is available to authorized users.