*Manrique, Gabriel; #Lorenzo, Marcelo Gustavo; # Diotaiuti, Lileia; *Lazzari, Claudio Ricardo and †Zani, Carlos Leomar

This work identifies the odors released by disturbed T. infestans adults, using the solid phase micro extraction (SPME) sampling technique. Couples (k = 5) were introduced into five 10 ml vials using pieces of filter paper to avoid pressing the insects with forceps. The vials were closed with a teflon/silicone lined cap and the insects disturbed by tapping during 20 sec. The headspace volatiles were sampled during 10 min ( 25 °C, 53-60 RH) using a 65 mm CAR/PDMS fiber (Supelco). Control samplings without insects were run prior to each series of analysis. The trapped volatiles were desorbed at 240 °C into the split-splitless (1:5) injector of a Shimadzu GC-MS (5050A) and separated in a Supelcowax-10 capillary column (30m x 0.25mm, 0.25µm) using a temperature program (80°C _ 240 °C_@ 10°C/min) and interface at 250 °C. The identity of the components was deduced by analysis of their mass spectra, comparison with the NIST Library of the equipment, and injection of commercial standards. Using this protocol, the volatiles found in the headspace of disturbed T. infestans were: 3-pentanone, isobutyl alcohol, isobutyl isobutyrate, 2-methyl-butyl alcohol, acetic acid, propionic acid, isobutyric acid, butyric acid, 2-methyl-butyric acid, and phenylethyl alcohol. Isobutyric acid was the major component of the mixture, as already described in the literature. 3-Pentanone, 2-methyl-butyl alcohol and 2-methyl-butyric acid were detected for the first time in disturbed T. infestans. SPME sampling showed effective as it allowed to detect previously described compounds as well new components in the volatile blend liberated by triatomines.
Support: PRONEX, FIOCRUZ, CONICET, Univ. Buenos Aires, CAPES/Antorchas and CAPES SCyT

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*Laboratorio de Fisiología de Insectos, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina, E-Mail:gabo@bg.fcen.uba.ar, Fax: (+54 11) 4576-3384)

#Laboratório de Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou, FIOCRUZ, Belo Horizonte, Minas Gerais, Brazil

† Laboratório de Química de Produtos Naturais, Centro de Pesquisas René Rachou, FIOCRUZ, Belo Horizonte, Minas Gerais, Brazil

J. Steven McElfresh and Jocelyn G. Millar

The saturniid moth Hemileuca eglanterina (Boisduval) appears to have at least two distinct pheromone types. Males from the San Gabriel Mountains of southern California are attracted optimally to a blend of E10,Z12-hexadecadienyl acetate (E10,Z12-16:Ac), E10,Z12-hexadecadienol (E10,Z12-16:OH), and E10,Z12-hexadecadienal (E10,Z12-16:Ald), whereas males from a Nevada population are attracted to the two-component blend of E10,Z12-16:OH and E10,Z12-16:Ald. Populations along the eastern edge of the Sierra Nevada Mountains contain both pheromone types, and an intermediate type. Antennae from the different pheromone types gave different EAG responses when challenged with blends of the pheromone components, with San Gabriel Mountains males showing a large response to E10,Z12-16:Ac and lesser responses to E10,Z12-16:OH and E10,Z12-16:Ald. In contrast, antennae from Nevada males exhibited a large response to E10,Z12-16:OH, a smaller response to E10,Z12-16:Ald, and minimal or no response to E10,Z12-16:Ac. Males from the eastern Sierra Nevada Mountains gave antennal responses similar to those of either San Gabriel Mountains or Nevada males. However, eastern Sierra populations also contain an intermediate type which does not occur in areas where the major pheromone types do not occur together. This third type may be a hybrid between the two other pheromone types, and it is attracted in approximately equal numbers to synthetic pheromone lures with and without E10,Z12-16:Ac. The existence of the different pheromone types, some of which are sympatric with closely related species, may represent a case of reproductive character displacement.

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Department of Entomology, University of California, Riverside CA, 92521, USA

J. A. Byers¹, Q. H. Zhang¹, G. Birgersson² & A. M El-Sayed³

A piezoelectric sprayer for dispensing semiochemicals in precise amounts was developed and used for a field test of bark beetle semiochemicals. The sprayer consists of a geared pump that pushes a syringe slowly to dispense semiochemicals in solvents through a micro-tube to a glass micropipette fixed to a piezoelectric high-frequency vibrator. The sprayer, syringe, pump, and electronics were hung on one arm of a rotating trap pair (traps 6 m apart) that was slowly rotated at 2 rph to even out the position effects on trap catches. The aggregation pheromone components of Pityogenes bidentatus (Hbst.) (Coleoptera: Scolytidae), grandisol and cis-verbenol, served as attractive baits against which various inhibitory treatments were tested. The release by the sprayer of (+)- and (-)-a-pinene, (+)-3-carene, and terpinolene, monoterpenes of host Scotch pine Pinus sylvestris L., at increasing rates from 0.01 to 10 log-equivalents in decadic steps (each at 0.1 to 100 µg/min) resulted in decreasing responses to aggregation pheromone (only 9% at highest rate). Inhibition by the individual monoterpenes tested at the 100 µg/min rate was significant for (+)- and (-)-a-pinene and terpinolene (12, 13, and 15% of control, respectively). Tests with bark strips from Norway spruce, Picea abies, Scotch pine, and birch, Betula pendula, showed them to significantly reduce response of bark beetles to pheromone. Avoidance of volatiles from nonhost trees appears clearly advantageous while the inhibition by the host Scotch pine monoterpenes may allow P. bidentatus to avoid resistant trees that release large amounts of toxic monoterpenes in their resin and instead colonize dying and diseased limbs or slash, the usual host substrate.

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¹Dept. Plant Protection, Swedish Univ. Agricul., SE 230 53 Alnarp, Sweden;

²Dept. Chem. Ecology, Göteborg Univ., SE 400 33 Göteborg, Sweden;

³Southern Crop Protection & Food Research Centre, Agricul. & Agri-Food Canada, Vineland Station, Ontario L0R 2E0, Canada

Joseph K. Staples #1, Bryan S. Krall #1, Robert J. Bartelt #2,

& Douglas W.Whitman #3

Secretions from the metathoracic glands (MTG) of the black locust bug Lopidea robiniae (Uhler) (Heteroptera: Miridae) contained six major compounds including, (E)-2-hexenal, (E)-2-hexenol, (E)-2-octenal, (E)-2-octenol, (E)-2-heptenal, and (?)-3-octenol. Males and females did not differ significantly in the relative compositions of identified compounds. Feeding trials with six bird species demonstrated feeding aversions towards L. robiniae suggesting that this bug is chemically defended. L. robiniae discharge the liquid contents of their MTG glands when attacked, producing a strong and distinct odor. A number of birds tested immediately ejected bugs out of their mouth after biting them, suggesting that the MTG secretions function as deterrents against predators.

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#1 4120 Biological Sciences Illinois State University Normal, Illinois 61790,

USA, E-mail: jstapl@ilstu.edu; #2 USDA, ARS National Center for Agricultural

Utilization Research, Bioactive Agents Research Unit, Peoria, IL 61604, USA,

E-mail bartelrj@mail.ncaur.usda.gov; #3 4120 Biological Sciences, Illinois

Sta. Univ., Normal, IL 61790, USA, E-mail dwwhitm@ilstu.edu, phone (309)-438-5123.

Judith Reinhard ¹, Michael Lenz ² & Michael Lacey ²

The labial gland secretion of termites contains a water soluble, persistent chemical signal, which is released by workers onto the food during feeding. It stimulates nestmates to feed at the same site. The chemical structure of this phagostimulant was identified by GC-MS. It is present in the labial glands of probably all termite species irrespective of their dietary habits (16 species representing all Isoptera families except the Serritermitidae analysed) in varying amounts. Choice tests with the phagostimulant on filter paper showed significant feeding stimulation for selected species in the range of the natural concentrations. Synergistic effects with further gland components were not evident so far. Chemically related compounds had some phagostimulating effect as well, indicating a rather unspecific signal receptor. The signal also works as short-range attractant: within a range of several cm termites orientate towards the signal source.

Laboratory and field trials in Australia and Southeast Asia, incorporating the phagostimulant into termite bait systems, showed that the number of termites as well as the amount of ingested bait material were in most trials significantly higher in the treated baits than in the controls. Furthermore, the signal proved to last for a few weeks under field conditions. Due to its general occurrence among termites and its durability, this phagostimulant has potential for global application in bait systems for termite management. A complete patent for the phagostimulant and related compounds has been filed.

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¹ current address: CNRS-LNB, 31 ch Joseph Aiguier, 13402 Marseille Cedex 20, France

² CSIRO Entomology, GPO Box 1700, Canberra, ACT 2601, Australia

HOW TOXIC ARE FRESH LEAVES OF PLANTS AGAINST UNADAPTED HERBIVORES?: A
Kotaro KONNO, Chikara HIRAYAMA, Masatoshi NAKAMURA

The assays of toxicity and anti-growth effects of chemical defense of plants against herbivores (low molecular weight chemicals or proteins) have been performed usually on artificial diets containing either substance extracted from plants or heat processed plant tissue. However, direct assays in which unadapted herbivores were fed fresh plant leaves have been difficult. This is due to the tendency that, when given certain plants, unadapted herbivores refuse to eat them, while adapted ones eat and grow well without showing any toxic effects. We recently found that the larvae of the Eri silkmoth, (Samia ricini, Saturniidae) eat fresh leaves of many unadapted plant species, and show a variety of biological effects corresponding to the plant species. For example, Sambucus sieboldiana (Caprifoliaceae) shows acute toxicity, Morus bombycis(Moraceae) and Carica papaya(Caricaceae) show toxicity and growth inhibitory effect, Ligustrum obtusifolium(Oleaceae) and Zingiber mioga(Zingiberaceae) show growth inhibitory effect, and Gardenia jasminoides (Rubiaceae) shows growth inhibitory effect and blackens the body color of the larvae. Interestingly, many of these effects are lost when these leaves are steamed for 4 min in 100ºC before the assays. The results from the Eri silkworm assays indicate that fresh leaves of many plant species have defense mechanisms that have been overlooked in ordinary methods.

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National Institute of Sericultural and Entomological Science, 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan. E-mail:konno@nises.affrc.go.jp

Lara Maistrello¹, Betty Zhu², Roger A. Laine² & Gregg Henderson¹

Vetiver oil is extracted from the roots of an Indian native grass (Vetiveria zizanioides), which is known to be naturally resistant to arthropod pests and diseases. Vetiver oil consists of a complex mixture of more than 300 compounds, half of which are reported to be sesquiterpenoid constituents. Nootkatone, one of the components, is a mildly pungent sesquiterpene ketone with a distinctive grapefruit flavor, largely responsible for the unique aroma of vetiver oil.

Our investigation aimed to test the effects of vetiver oil and its components on the Formosan subterranean termite, the major insect pests in the southern United States. The results showed that nootkatone and other natural components of vetiver oil negatively affect termite physiology and behavior, as a consequence of direct physical contact, ingestion, or exposure to the vapors. Especially interesting are the effects of nootkatone: in the presence of this compound termites were not able to dig tunnels or to build shelter tubes. We tested if nootkatone acts as simply an inhibitor of termite mobility or as a modifier of chemical signals important for communication between colony members.

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¹Dept. of Entomology, 402 Life Sciences Bldg., Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA

lmaistrello@agctr.lsu.edu

²Dept. of Biological Sciences, 320 Choppin Hall, Louisiana State University, Baton Rouge, LA 70803, USA

Letizia Mattiacci, Sara Rudelli, Silvia Dorn

Brussels sprouts plants attacked by Pieris brassicae caterpillars release volatiles that attract a natural enemy of the herbivores, the parasitoid Cotesia glomerata, to the damaged plant. In a previous study we observed that feeding by caterpillars on the lower leaves triggers the systemic release of volatiles detectable by the parasitoids from upper leaves of the same plant. Volatile release occurs only after at least three days of continuous feeding on the lower leaves and only if further mechanical damage is inflicted on the systemically induced upper leaves.

The aim of this study was to elucidate whether the systemically induced response in cabbage upon herbivory might affect the fitness of the herbivore, providing thus an inducible defense. Results show that the Pieris brassicae, even though it is a specialist herbivore on cabbage, is behaviourally and physiologically affected by the inducible response. The potential of this response as an effective defense of cabbage plants against specialist and generalist herbivores is discussed.
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Institute of Plant Sciences / Applied Entomology, Swiss Federal Institute of Technology (ETH), Clausiusstrasse 25/NW, CH 8092 Zurich, Switzerland

Arnaud Ludovic¹, Lognay Georges.², Leenaers Lionel¹, Gaspar Charles¹ & Haubruge Eric¹

flour beetles are cosmopolitan in distribution and are very commonly found in grain stores and flour mills. Their ability to exploit a wide variety of stored products has contributed to their status of major pest of stored food. Both adult and larvae share the same habitat, and insects of more than one species can be observed in the same place. However, some of these species (T. castaneum, T. confusum and T. freemani) were observed to share the same aggregation pheromone, the (4,8) dimethyldecanal. Moreover, cross attraction was previously observed between some species; but, it was not reciprocal for every species tested. This phenomenon would lead to imperfect reproductive isolation between the species. Also, sterile hybrid are observed between T. castaneum and T. freemani.

In the present study, the volatile produced by adult male and female of eight Tribolium species (Tribolium castaneum, red flour beetle, T. confusum, confused flour beetle, T. anaphe, T. brevicornis, giant flour beetle, T. freemani, T. destructor, dark flour beetle, T. madens, black flour beetle and T. audax, american flour beetle) have been analyzed by solid phase micro-extraction (SPME) and GC-MS. Experiments were conducted in order to (1) identify the aggregation pheromone emitted by the adults of the different species, (2) observe whether or not all these species biosynthetize possess a common semiochemical, and (3) if other volatile molecules which could be involved in the reproductive isolation of the species, are produced in some species.

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¹Unit of pure and applied Zoology, ²Unit of pure and organic Chemistry

Gembloux Agricultural University - Passage des Déportés 2, 5030 Gembloux, Belgium

arnaud.l@fsagx.ac.be

M.Ozaki, Y.Kawahara, K.Nakamura, K.Shiraishi, A. M.Kakiuchi, A.Wada & R.Yamaoka

Odor of limonene, a monoterpene component in lemon or bergamot oil is not hatable or harmful for humans. However, the blowflies, when exposed to the odor of limonene for a few days, showed long lasting sever appetite reduction. Thus, the appetite reduction may be one of the defensive reactions against toxicity of limonene via their olfactory system. As oral administration of limonene is actually fatal for the blowflies, we presumed that their taste system could also detect noxious lipophilic substances to avoid swallowing them as a fail-safe. However, studies on taste reception to lipophilic and toxic substances have not been reported so much because of difficulties in preparing stimuli with lipophilic substances and in keeping animals in good condition during the experiments with toxic stimuli.

When we touched the labellar chemosensilla with the limonene-dispersing solution, the fly exhibited irritating proboscis extension with regurgitation. It looked a defensive behavior against toxic substances.

In our electrophysiological experiments, the impulses induced by limonene were specifically generated from the fourth taste receptor cell, whose specific function had not been defined. Thus, we suggested that the fourth taste cell responds to lipophilic substances and that one of its important functions is generation of warning impulses to noxious substances like limonene.
This study was supported by HFSP grant to M.O.
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Lab. of Chemical Ecology, Kyoto Institute of Technology, Kyoto, 606-8585 Japan

mamiko@ipc.kit.ac.jp

Manfred Ayasse, Florian Schiestl, Fernando Ibarra and Wittko Francke

Ophrys orchids are pollinated by males of bees, wasps and beetles. Copulatory behavior is elicited by the scent produced by the flowers. In two species of Ophrys, we investigated floral scent emission and attractiveness after pollination. We analyzed and compared floral odor of unpollinated and pollinated flowers by GC-MS and GC-EAD. In O. sphegodes, odor samples showed significantly higher amounts of all-trans-farnesyl hexanoate after pollination. Farnesyl hexanoate is a major constituent of the Dufour's gland secretion in mated, breeding females of the pollinator bee, Andrena nigroaenea, where it functions in lining of brood cells. In behavioral experiments this compound inhibits copulation attempts in males. In dual-choice tests, flowers which were artificially scented with farnesyl hexanoate equal to the increased amount after pollination, were significantly less attractive than flowers treated with solvent only. O. speculum, a second species we studied, is pollinated by males of the scoliid wasp C. ciliata. The attractiveness of its flowers is diminished after pollination due to smaller amounts of the male attracting compounds, mainly hydroxy acids. We propose that pollinated flowers in both species mimic the scent of mated females in order to guide pollinators to unpollinated flowers of the inflorescence. This results in an increase of the reproductive success of a plant.

Supported by a grant of the FWF Austria (P12275-BIO)
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Institute of Zoology, Althanstrasse 14, A-1090 Vienna, Austria

Institute for Organic Chemistry, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany.

Maria Elena Fritzsche-Hoballah, Cristina Tamò and Ted Turlings

Herbivore-induced plant volatiles have been suggested to function as indirect defense signals that attract natural enemies of herbivores. Several insect parasitoids are known to exploit such plant-provided cues to locate their hosts. One such parasitoid is the generalist Cotesia marginiventris (Hymenoptera: Braconidae), which is attracted to herbivore-induced maize volatiles. Maize plants can be induced to produce the same volatiles by treating them with regurgitant of Spodoptera species. It is known that these artificially induced plants can be as attractive to this parasitoid as the complete plant-herbivore complex. We analyzed the artificially induced emissions of 8 Mexican maize varieties and found significant differences among their volatile profiles. The same artificially induced Mexican varieties were offered in dual choice experiments, in a y-tube olfactometer, to naive mated females of C. marginiventris. Preference for certain maize varieties were related to their odor profiles. The results are discussed in relation to the possibility to select crop varieties that are particularly attractive to parasitoids and could, therefore, be more effectively used in integrated pest management.

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Université de Neuchâtel, Institut de Zoologie, Laboratoire d'Ecologie Animale et Entomologie (LEAE), Case Postale 2, 2007 Neuchâtel, Switzerland. Tel: 0041 32 718 3164, Fax: 0041 32 718 3001, Email: maria.fritzsche@zool.unine.ch

D.M. Suckling¹, A.R. Gibb¹, J.M. Daly¹, E.G. Brockerhoff², and X. Chen¹

The electrophysiological responses of adult burnt pine longhorn beetles were recorded to a range of odourants. Similar responses were recorded to most monoterpenes recorded from Pinus radiata, with the exception of a-terpineol, which gave much greater responses in both sexes. Green leaf volatiles also gave high responses. Actinograph recordings of caged individuals showed that males and females were most active from dusk to midnight. Olfactometer experiments indicated that females moved upwind to odours from burnt compared to unburnt pine. Oviposition choice tests showed that with eggs were predominantly laid on burnt compared to unburnt logs. Beetles were trapped by funnel traps baited with burnt (mean 7.8 beetles) and unburnt (mean 4.1 beetles) pine bark from inside an outdoor screen cage, while unbaited traps had a mean catch 0.1 beetles. The treatment of burnt pine bark with a repellent reduced trap catch by five-fold in a similar experiment (mean catches of 1.2 (burnt pine bark plus repellent treatment) and 6.2 burnt pine bark alone), indicating a degree of repellency of females overiding attraction. The treatment of burnt pine bark with a repellent reduced oviposition by 98.5%, indicating that oviposition cues have potential to be significantly disrupted. The potential exists to improve the management of this insect using chemical cues in various ways.
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¹HortResearch, PO Box 51, Lincoln, Canterbury, New Zealand

²Forest Research, PO Box 29237, Christchurch 8004, New Zealand

M. A. Carlsson, B. S. Hansson

The primary centra for olfactory processing in an insect brain are the antennal lobes. In the lobes, olfactory receptor neurons converge on spherical neuropils called glomeruli where synapses are made with higher order neurons. The function of glomeruli has for a long time been a question of paramount interest. Do receptor neurons terminate in a diffuse way in all glomeruli or does a certain glomerulus represent a specific receptor type, i.e. that glomeruli are functional units. To answer this question we have optically measured calcium activity in vivo in the moth Spodoptera littoralis.

Different odorants evoked different activity patterns that were consistent between individuals. Certain odorants showed response in distinct parts of the lobe but the activity patterns of many odorants were overlapping suggesting that the same glomeruli were activated by several odorants. The sex pheromone components elicited strong response in males only in the area close to the antennal nerve where the male-specific macroglomerular complex (MGC) is located. The individual components of the pheromone activated different parts of the MGC area. Plant and flower odours did normally not activate this area.

Two extremes of information coding schemes in the antennal lobes have been proposed. In a labeled line system each glomerulus should represent a specific odorant with no overlap whereas in across-fiber coding an odour is represented by a combination of activity in a number of glomeruli. Our results suggest that both strategies are used. But all odorants tested evoked distinct, reproducable patterns which indicates that the identity of an odorant is encoded in the lobe.
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Department of Ecology, Lund University, S-223 62 Lund Sweden

Caroline Müller, Alan Renwick

In the past decades, several studies have focused on the identification of feeding stimulants for specialists that feed on solanaceous plants, especially potato (Solanum tuberosum). Two insects are devastating for this crop plant: the Colorado potato beetle, Leptinotarsa decemlineata L. (Coleoptera: Chrysomelidae), and the tobacco hornworm, Manduca sexta (Johan) (Lepidoptera: Noctuidae). In the 1950's, a phagostimulant was isolated from potato and tomato for M. sexta and characterised as a glycoside. It was suggested that the specific stimulants for M. sexta and L. decemlineata are identical. But the chemical structure has not yet been elucidated. Recent work in our lab (del Campo & Renwick) has resulted in the isolation and characterization of a phagostimulant for M. sexta from potato. We have now investigated whether this compound does in fact also stimulate feeding by L. decemlineata or if other phagostimulants are involved. For both insects, different dual-choice bioassays were conducted. For M. sexta, cowpea leaf discs served as a substrate to test extracts. In a new bioassay for L. decemlineata we utilized starch and wheat-flour based wafers as a neutral substrate. Our results indicate that the phagostimulant isolated for M. sexta is also stimulatory for adult L. decemlineata, but only at high concentrations. Other, more polar compounds show stimulatory activity at lower concentrations for L. decemlineata. Finally, it appears that for M. sexta, more than one compound is phagostimulatory.

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Boyce Thompson Institute for Plant Research, Tower Rd., Ithaca, NY 14853, USA; cm227@cornell.edu

Chemical Variability and Ecological Roles.

Monica Puyana and William Fenical

The genus Aplysina is well defined both morphologically and chemically. These sponges contain an elaborate series of brominated metabolites derived from tyrosine which exhibit a wide spectrum of biological activity in in-vitro assays. It has been assumed that organisms rich in bioactive secondary metabolites have defensive or competitive advantages over organisms they interact with. However, only until these assumptions are tested in an ecologically relevant setting we will be able to assign ecological roles to these compounds. We are investigating the chemical composition, chemical variability and mechanisms of chemical defense of six species of the genus Aplysina. In these sponges usually 8-10 major metabolites occur in complex mixtures at high concentrations. To assess the possibility of an induced defense, we simulated "attacks" on the sponges and did not detect significant differences over time in their overall chemical constitution. Using a fish feeding bioassay we have determined that mixtures are more feeding deterrent than pure compounds, possibly due to a synergistic or reinforcing effect with other chemical constituents in the sponges. Chemical defense against microbial invasion was determined using a liquid culture assay with microbial strains isolated from healthy and decaying sponges. We observed that antibacterial activity is highly dependent on the test strains used. Highly resistant strains have been isolated from lesions or necrotic tissues of Aplysina. Strains isolated from decaying unrelated sponges (not Aplysina spp.) are very sensitive to these metabolites, suggesting that agents of disease and degradation in sponges may be species-specific and in some instances may circumvent or resist the chemical defenses of sponges.

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The host-plant finding behaviour in walking Oreina cacaliae (Chrysomelidae) was studied in the field, to test the importance of olfaction is this process. A total of 200 marked adult beetles were released under different wind directions on a selected site surrounded by their host plant Adenostyles alliariae. Locations of the beetles on the host plants were recorded at the day of release and once a week during three successive weeks. Analysis of the data by circular statistics revealed that the movement of the beetle was dependent on the wind direction: under northwind conditions the majority of the beetles was found northeast of the release point, in contrast, beetles moved southeast, when the wind blew from the south. Because 96% of 200 beetles released in an identical visual surrounding moved to host plants in the upwind direction, we conclude that host plant finding of O. cacaliae relies on olfaction rather than on vision.

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Institut de Zoologie, Rue Emile Argand 11, 2000 Neuchâtel

Qing-He Zhang and Fredrik Schlyter

Insects are attracted to their host plants by host odours for feeding and egg-laying. A prominent example is attraction to monoterpenes by conifer-inhabiting bark beetles. Odors from non-host plants were believed not to be of importance or reacted upon only at close distance. To understand the potential roles of nonhost volatiles (NHVs) in the host selection of the European conifer bark beetles, Ips typographus, I. duplicatus, Tomicus piniperda and T. minor, an intensive study in both lab and field has been carried out. GC-EAD analysis of nonhost Betula pendula, B. pubescens and Populus tremula aeration samples indicated that antennae of these bark beetles consistently responded to C₆-alcohols:1-hexanol and (Z)-3-hexen-1-ol (from both leaves and bark), and (E)-2-hexen-1-ol (from leaves); and C₈-alcohols (from bark): 3-octanol and 1-octen-3-ol. trans-Conophthorin from the nonhost bark also elicited strong EAD response in I. typographus and I. duplicatus, but was antennally inactive in the Tomicus species. In field trapping tests, the EAD-active NHVs (alone or combined) significantly reduced the attraction of these bark beetles to their pheromone/kairomone components. A strong synergistic effect between the active NHVs and verbenone (a host unsuitability signal) was also found. Our results suggest that these nonhost leaf and bark volatiles are important olfactory signals used by these conifer bark beetles in descriminating between host and nonhost trees and habitats. Further study on the potential use of these NHVs in semiochemical-based management against these European conifer bark beetles is under way.

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Chemical Ecology, Department of Plant Protection Sciences, Swedish University of Agricultural Sciences, Box 44, 230 53 Alnarp, Sweden

In ants, the social environment influences the physiology and behavior of the individuals. Mated queens Solenopsis invicta produce primer pheromones that are distributed by workers and inhibit the ovary development and dealation of virgin females. However, what mediates the response of allate females at the individual level is poorly documented. Using HPLC-ECD we demonstrate that virgin females isolated from the queen pheromone(s) influence have a higher level of dopamine than virgin females of the same age that were maintained in the colony (531 ± 25 vs 816 ± 64 fMol/brain respectively). Levels of octopamine and serotonin were not modified by the isolation from the queen pheromone.

The increase of the dopamine level occurred in 5 days, which corresponds, to time necessary for virgin female dealation and ovary development.

These results, together with previous ones obtained by Harris and Woodring (1995) in the honeybee indicate that brain dopamine could participate to the activation of ovarian development in the absence of the queen pheromone in some social Hymenoptera.

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Department of Entomology, 402 Life Sciences Building, Louisiana State University, LA 70803 Bâton Rouge USA

Ritsuo Nishida¹ and Tan, Keng Hong²

The solitary flower of Bulbophyllum patens King (Orchidaceae) selectively attract male fruit flies of several Bactrocera species with a specific fragrance in the rain-forest of Malaysia. It temporarily trap flies between its hinged see-saw lip and column for pollination. The attractant component was identified as zingerone [4-(4-hydroxy-3-methoxyphenyl)-2-butanone], a pungent essence of ginger. Zingerone conforms to a structure resembling two major fruit fly attractants (methyl eugenol and raspberry ketone) and thus showed a potency to attract a wider range of fruit fly species (B. papayae, B. carambolae, B. umbrosa, B. cucurbitae, B. tau and B. caudata). This appeared to be the first example of an attractant which exerts activity both on the methyl eugenol- and raspberry ketone-sensitive Bactrocera fruit flies. A fruit fly visitor is rewarded by feeding on zingerone and in return it helps in pollination by removing the pollinarium and then transferring it to another flower. Males of the melon fly acquired the floral essence and selectively stored it in the pheromone gland to attract conspecific females. Male of B. papayae, however, converted zingerone to zingerol in the crop. The latter compound was stored in the rectal gland and subsequently released to attract females. This provides a rare example of a mutualistic interaction between insects and plants via a floral synomone, in which both organisms obtain advantages directly benefiting their reproductive systems.

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¹Lab of Chemical Ecology, Graduate School of Agriculture, Kyoto Univ., Kyoto, 606-8502, Japan ritz@kais.kyoto-u.ac.jp

²School of Biological Sciences, Univ. of Science Malaysia, 11800 Penang, Malaysia

Four host plants, while damaged by black vine weevil (Otiorhynchus sulcatus) were tested in a dual-choice olfactometer. Only Taxus baccata and Euonymus fortunei attracted large number of weevils. Fragaria x ananassa and Rhododendron were not attractive. The volatile attraction to Taxus and Euonymus is well related to the feeding preference and oviposition of the black vine weevil on these crops. Undamaged Euonymus in the presence of weevils was not attractive whereas Euonymus freshly damaged by weevils attracted weevils. The high EAG response for several green leaf volatiles and the bioassay result suggest an important role of these volatiles in attraction to host plants. Some other attractive or repelling substances in plants probably also affect attraction since weevil-damaged Rhododendron and Fragaria are not attractive. Further a positive correlation between weevil/frass odour and attraction was found in the control treatment and a treatment with pre-damaged Euonymus. It is concluded that feeding-induced volatiles are involved in host finding of this parthenogenetic weevil species.

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¹ Research Station for Nursery Stock, P.O.Box 118, 2770 AC Boskoop, The Netherlands

² Plant Research International, P.O.Box 16, 6700 AA Wageningen, The Netherlands

³ University of Amsterdam, Dept. of Pure and Appl. Ecology, Kruislaan 320, 1098 SM Amsterdam, The Netherlands

A Y-tube was developed to test the olfactory responses of Heterorhabditis megidis. The olfactory cues tested were rooted cuttings of Thuja occidentalis cv. Smaragd, Taxus baccata, strawberry plants (Fragaria x ananassa cv. Senga sengana), black vine weevils (Otiorhynchus sulcatus) and wax moth larvae (Galleria mellonella).

Both insect species, Thuja and Taxus were attractive for H. megidis. Strawberry was not attractive. Combining Thuja or Taxus with black vine weevil larvae improved the attraction. We found a strong preference of H. megidis for the combination Thuja with larvae on roots versus roots or larvae alone. Further testing showed that Thuja plants, pre-damaged by larvae, were preferred to undamaged or mechanically damaged plants.

This is the first report of a semiochemical-mediated attraction of entomopathogenic nematodes to herbivore feeding-induced root compounds. So far little attention has been paid to semiochemicals in the tritrophic model plant-weevil-Heterorhabditis. The developed Y-tube is a useful instrument for future chemical ecological studies with nematodes. Understanding the mechanisms of semiochemical communication and determining the attractants involved will have a large impact on selection and improvement of the efficacy of nematode strains for biological control.

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¹ Research Station for Nursery Stock, P.O. Box 118, 2770 AC Boskoop, The Netherlands

² Wageningen-UR, Department of Nematology, P.O. Box 8123, 6700 ES Wageningen, The Netherlands

³ Plant Research International, P.O. Box 16, 6700 AA Wageningen, The Netherlands

Robert P. Doss^1,2, James E. Oliver³ and William M. Proebsting²

Bruchins, long-chain a,w-diols, mono- or diesterified with 3-hydroxypropanoic acid, were originally isolated from two bruchid species. Oviposition by one of these insects, the pea weevil, on pods of pea carrying the Neoplastic pod (Np) gene results in formation of masses of undifferentiated cells (calli) beneath the eggs. These calli inhibit larval entry into the pod. Thus, bruchins, the compounds responsible for stimulating cell division and callus formation, are potent plant mitogens that mediate an interesting form of induced resistance to an insect. We have used Differential Display with mRNA from near isogenic lines of pea carrying either the Np or the np allele to study some genetic aspects of the response of pea pods to bruchin application. Patterns that imply strong up-regulation of genes after bruchin treatment have been noted, as have patterns that imply constitutive expression of genes by Np pods, but not np pods, and vice versa. We are currently cloning some of the differentially displayed cDNA fragments with the hope that identification of the genes whose expression is varied either by bruchin treatment or by genetic constitution will shed light on bruchin mechanism-of-action. Another thrust of our work is to determine whether or not bruchins are normal constituents of plants. Very preliminary evidence indicates that they may be, in which case they could function as endogenous plant regulators.

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¹Horticultural Crops Research Unit, USDA-ARS, Corvallis, OR 97330, USA

²Insect Chemical Ecology Laboratory, USDA-ARS, Beltsville, MD 20705, USA

³Department of Horticulture, Oregon State University, Corvallis, OR 97331, USA