Identification of Floral Volatiles and Pollinator Responses in Kiwifruit Cultivars, <Emphasis Type="Italic">Actinidia chinensis</Emphasis> var. <Emphasis Type="Italic">chinensis</Emphasis>

Volatiles emitted from unpollinated in situ flowers were collected from two male cultivars, ‘M33’, ‘M91’, and one female cultivar ‘Zesy002’ (Gold3) of kiwifruit (Actinidia chinensis var. chinensis). The samples were found to contain 48 compounds across the three cultivars with terpenes and straight chain alkenes dominating the headspace. Electrophysiological responses of honey bees (Apis mellifera) and bumble bees (Bombus terrestris) to the headspace of the kiwifruit flowers were recorded. Honey bees consistently responded to 11 floral volatiles from Gold3 pistillate flowers while bumble bees consistently responded to only five compounds from the pistillate flowers. Nonanal, 2-phenylethanol, 4-oxoisophorone and (3E,6E)-α-farnesene from pistillate flowers elicited responses from both bee species. Overall, honey bees were more sensitive to the straight chain hydrocarbons of the kiwifruit flowers than the bumble bees, which represented one of the main differences between the responses of the two bee species. The floral volatiles from staminate flowers of the male cultivars ‘M33’ and ‘M91’ varied greatly from those of the pistillate flowers of the female cultivar Gold3, with most of the bee active compounds significantly different from those in the Gold3 flower headspace. The total floral emissions of ‘M33’ flowers were significantly less than those of the Gold3 flowers, while the total floral emissions of the ‘M91’ flowers were significantly greater than those of the Gold3 flowers.     

Flower Visitors of <Emphasis Type="Italic">Campanula</Emphasis>: Are Oligoleges More Sensitive to Host-Specific Floral Scents Than Polyleges?

The pollen diet provided by adult bees to their offspring varies immensely. While some species collect pollen on several plants irrespective of their phylogenetic relatedness (polyleges), others collect only on plants within a genus or family (oligoleges). Floral scents play a central role in bee-plant interactions. To locate flowers, polyleges are assumed to rely on compounds commonly found as floral scent constituents, whereas oligoleges rely on unusual compounds to recognize host flowers unambiguously. Campanula flowers are visited by both polylectic and oligolectic species, and their scent bouquets consist of common and unusual (e.g., spiroacetals) volatiles. In a comparative approach, we performed electroantennographic analyses to investigate the antennal responses of three polyleges and three oligoleges to three common volatiles and four spiroacetals. We hypothesized that: 1) oligoleges and polyleges should respond similarly to common flower volatiles, and 2) Campanula oligoleges should be more sensitive to spiroacetals than are polyleges. In corroboration, we found that antennal sensitivity to common volatiles was similar among bees irrespective of pollen diet, whereas oligoleges of Campanula were more sensitive to spiroacetals than polyleges. Newly emerged bees of the Campanula oligolege Chelostoma rapunculi rely on spiroacetals for recognizing host-flowers, and our results suggest that this might also be true for other Campanula oligoleges, since Chelostoma campanularum and Hoplitis mitis also were able to perceive these specific volatiles at very low concentrations. Together, our results provide interesting insights into the significance of olfactory adaptations in oligolectic and polylectic bee species.     

The Role of Leaf Volatiles of <Emphasis Type="Italic">Ludwigia octovalvis</Emphasis> (Jacq.) Raven in the Attraction of <Emphasis Type="Italic">Altica cyanea</Emphasis> (Weber) (Coleoptera: Chrysomelidae)

Larvae and adults of Altica cyanea (Weber) (Coleoptera: Chrysomelidae) feed on the rice-field weed Ludwigia octovalvis (Jacq.) Raven (Onagraceae), commonly known as willow primrose, which is considered a biocontrol agent of the weed. Volatile organic compounds from undamaged plants, plants after 4, 12, and 36 h of continuous feeding by A. cyanea larvae or adult females and after mechanical damaging were identified by GC-MS and GC-FID analyses. Twenty nine compounds were identified from undamaged plants. 2Z–Penten-1-ol, geraniol, and 1-tridecanol were present in all plants damaged by larvae. In contrast, feeding by adults caused the release of 2Z–penten-1-ol only after 12 and 36 h; whereas geraniol and 1-tridecanol appeared only after 36 h. Farnesyl acetone was detected after 12 and 36 h of feeding by larvae and after 36 h of feeding by adults. Farnesene was detected after 36 h of feeding by larvae and adults. Linalool was unique after 36 h of feeding by larvae. In Y-shaped glass tube olfactometer bioassays, A. cyanea females were attracted to volatiles after 36 h of feeding by larvae or adults compared to volatiles released by undamaged plants. The insects were attracted to five synthetic compounds: 3-hexanol, α-pinene, linalool oxide, geraniol, and phytol. Synthetic blends were more attractive than individual compounds. Compared to undamaged plants, volatiles released by plants, damaged by conspecific individuals, were more attractive to A. cyanea females, due to elevated emissions of 3-hexanol, α-pinene, linalool oxide, geraniol, and phytol.     

Volatiles of <Emphasis Type="Italic">Solena amplexicaulis</Emphasis> (Lam.) Gandhi Leaves Influencing Attraction of Two Generalist Insect Herbivores

Epilachna vigintioctopunctata Fabr. (Coleoptera: Coccinellidae) and Aulacophora foveicollis Lucas (Coleoptera: Chrysomelidae) are important pests of Solena amplexicaulis (Lam.) Gandhi (Cucurbitaceae), commonly known as creeping cucumber. The profiles of volatile organic compounds from undamaged plants, plants after 48 hr continuous feeding of adult females of either E. vigintioctopunctata or A. foveicollis, by adults of both species, and after mechanical damaging were identified and quantified by GC-MS and GC-FID analyses. Thirty two compounds were detected in volatiles of all treatments. In all plants, methyl jasmonate was the major compound. In Y-shaped glass tube olfactometer bioassays under laboratory conditions, both insect species showed a significant preference for complete volatile blends from insect damaged plants, compared to those of undamaged plants. Neither E. vigintioctopunctata nor A. foveicollis showed any preference for volatiles released by heterospecifically damaged plants vs. conspecifically damaged plants or plants attacked by both species. Epilachna vigintioctopunctata and A. foveicollis showed attraction to three different synthetic compounds, linalool oxide, nonanal, and E-2-nonenal in proportions present in volatiles of insect damaged plants. Both species were attracted by a synthetic blend of 1.64 μg linalool oxide?+?3.86 μg nonanal?+?2.23 μg E-2-nonenal, dissolved in 20 μl methylene chloride. This combination might be used as trapping tools in pest management strategies.     

Sexual Deception in the <Emphasis Type="Italic">Eucera</Emphasis>-Pollinated <Emphasis Type="Italic">Ophrys leochroma</Emphasis>: A Chemical Intermediate between Wasp- and <Emphasis Type="Italic">Andrena-</Emphasis>Pollinated Species

Ophrys flowers mimic sex pheromones of attractive females of their pollinators and attract males, which attempt to copulate with the flower and thereby pollinate it. Virgin females and orchid flowers are known to use the same chemical compounds in order to attract males. The composition of the sex pheromone and its floral analogue, however, vary between pollinator genera. Wasp-pollinated Ophrys species attract their pollinators by using polar hydroxy acids, whereas Andrena-pollinated species use a mixture of non-polar hydrocarbons. The phylogeny of Ophrys shows that its evolution was marked by episodes of rapid diversification coinciding with shifts to different pollinator groups: from wasps to Eucera and consequently to Andrena and other bees. To gain further insights, we studied pollinator attraction in O. leochroma in the context of intra- and inter-generic pollinator shifts, radiation, and diversification in the genus Ophrys. Our model species, O. leochroma, is pollinated by Eucera kullenbergi males and lies in the phylogeny between the wasp and Andrena-pollinated species; therefore, it is a remarkable point to understand pollinator shifts. We collected surface extracts of attractive E. kullenbergi females and labellum extracts of O. leochroma and analyzed them by using gas chromatography with electroantennographic detection (GC-EAD) and gas chromatography coupled with mass spectrometry (GC-MS). We also performed field bioassays. Our results show that O. leochroma mimics the sex pheromone of its pollinator’s female by using aldehydes, alcohols, fatty acids, and non-polar compounds (hydrocarbons). Therefore, in terms of the chemistry of pollinator attraction, Eucera-pollinated Ophrys species might represent an intermediate stage between wasp- and Andrena-pollinated orchid species.     

Electrophysiological and Oviposition Responses of <Emphasis Type="Italic">Tuta absoluta</Emphasis> Females to Herbivore-Induced Volatiles in Tomato Plants

In response to attack by herbivorous insects, plants produce semiochemicals for intra- and interspecific communication. The perception of these semiochemicals by conspecifics of the herbivore defines their choice for oviposition and feeding. We aimed to investigate the role of herbivore-induced plant volatiles (HIPVs) by Tuta absoluta larvae on the oviposition choice of conspecific females on tomato plants. We performed two- choice and non-choice bioassays with plants damaged by larvae feeding and intact control plants. We also collected headspace volatiles of those plants and tested the response of female antennae on those blends with Gas Chromatography- Electro-Antennographical Detection (GC-EAD). In total 55 compounds were collected from the headspace of T. absoluta larvae-infested plants. Our results show that female moths preferred to oviposit on intact control plants instead of damaged ones. Herbivory induced the emission of hexanal, (Ζ)-3-hexen-1-ol, (E)-β-ocimene, linalool, (Z)-3-hexenyl butanoate, methyl salicylate, indole, nerolidol, guaidiene-6,9, β-pinene, β-myrcene, α-terpinene, hexenyl hexanoate, β-elemene, β-caryophyllene and (Ε-Ε)- 4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT), one unidentified sesquiterpene and three unknown compounds. In Electroantennographic (EAG) assays, the antennae of T. absoluta females responded to hexanal, (Ζ)-3-hexen-1-ol, methyl salicylate and indole. The antennae of T. absoluta females exhibited a dose-response in EAG studies with authentic samples. Strong EAG responses were obtained for compounds induced on damaged tomato plants, as well as in nonanal, a compound emitted by both infested and control plants. These compounds could be utilized in integrated pest management of T. absoluta.     

Attraction of Three Mirid Predators to Tomato Infested by Both the Tomato Leaf Mining Moth <Emphasis Type="Italic">Tuta absoluta</Emphasis> and the Whitefly <Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Plants emit volatile compounds in response to insect herbivory, which may play multiple roles as defensive compounds and mediators of interactions with other plants, microorganisms and animals. Herbivore-induced plant volatiles (HIPVs) may act as indirect plant defenses by attracting natural enemies of the attacking herbivore. We report here the first evidence of the attraction of three Neotropical mirid predators (Macrolophus basicornis, Engytatus varians and Campyloneuropsis infumatus) toward plants emitting volatiles induced upon feeding by two tomato pests, the leaf miner Tuta absoluta and the phloem feeder Bemisia tabaci, in olfactometer bioassays. Subsequently, we compared the composition of volatile blends emitted by insect-infested tomato plants by collecting headspace samples and analyzing them with GC-FID and GC-MS. Egg deposition by T. absoluta did not make tomato plants more attractive to the mirid predators than uninfested tomato plants. Macrolophus basicornis is attracted to tomato plants infested with either T. absoluta larvae or by a mixture of B. tabaci eggs, nymphs and adults. Engytatus varians and C. infumatus responded to volatile blends released by tomato plants infested with T. absoluta larvae over uninfested plants. Also, multiple herbivory by T. absoluta and B. tabaci did not increase the attraction of the mirids compared to infestation with T. absoluta alone. Terpenoids represented the most important class of compounds in the volatile blends and there were significant differences between the volatile blends emitted by tomato plants in response to attack by T. absoluta, B. tabaci, or by both insects. We, therefore, conclude that all three mirids use tomato plant volatiles to find T. absoluta larvae. Multiple herbivory did neither increase, nor decrease attraction of C. infumatus, E. varians and M. basicornis. By breeding for higher rates of emission of selected terpenes, increased attractiveness of tomato plants to natural enemies may improve the effectiveness of biological control.     

Innate and Learned Prey-Searching Behavior in a Generalist Predator

Early colonization by Zyginidia scutellaris leafhoppers might be a key factor in the attraction and settling of generalist predators, such as Orius spp., in maize fields. In this paper, we aimed to determine whether our observations of early season increases in field populations of Orius spp. reflect a specific attraction to Z. scutellaris-induced maize volatiles, and how the responses of Orius predators to herbivore-induced volatiles (HIPVs) might be affected by previous experiences on plants infested by herbivorous prey. Therefore, we examined the innate and learned preferences of Orius majusculus toward volatiles from maize plants attacked by three potential herbivores with different feeding strategies: the leafhopper Z. scutellaris (mesophyll feeder), the lepidopteran Spodoptera littoralis (chewer), and another leafhopper Dalbulus maidis (phloem feeder). In addition, we examined the volatile profiles emitted by maize plants infested by the three herbivores. Our results show that predators exhibit a strong innate attraction to volatiles from maize plants infested with Z. scutellaris or S. littoralis. Previous predation experience in the presence of HIPVs influences the predator’s odor preferences. The innate preference for plants with cell or tissue damage may be explained by these plants releasing far more volatiles than plants infested by the phloem-sucking D. maidis. However, a predation experience on D. maidis-infested plants increased the preference for D. maidis-induced maize volatiles. After O. majusculus experienced L3-L4 larvae (too large to serve as prey) on S. littoralis-infested plants, they showed reduced attraction toward these plants and an increased attraction toward D. maidis-infested plants. When offered young larvae of S. littoralis, which are more suitable prey, preference toward HIPVs was similar to that of naive individuals. The HIPVs from plants infested by herbivores with distinctly different feeding strategies showed distinguishable quantitative differences in (Z)-3-hexenal, (E)-2-hexenal, and methyl salicylate. These compounds might serve as reliable indicators of prey presence and identity for the predator. Our results support the idea that feeding by Z. scutellaris results in the emission of maize’s HIPVs that initially recruit Orius spp. into maize fields.     

Fatal Attraction: <Emphasis Type="Italic">Ricinus communis</Emphasis> Provides an Attractive but Risky Mating Site for <Emphasis Type="Italic">Holotrichia parallela</Emphasis> Beetles

The castor bean, Ricinus communis L., is a non-host plant for the large black chafer, Holotrichia parallela Motschulsky (Coleoptera: Scarabaeidae). In laboratory bioassays we found that this plant was no less attractive than the main host plant (peanut, Arachis hypogaea) and three food plant species: velvetleaf (Abutilon theophrasti), the glossy privet (Ligustrum lucidum), and the Siberian elm (Ulmus pumila). In field trapping experiments a Soxhlet extract of castor bean leaves caught more beetles than the optimal sex lure blend [(R)-(?)-linalool and (L)-isoleucine methyl ester blended in a ratio of 1:4], compared at equal doses (500 μl), and laboratory bioassays indicated that a castor bean plant could enhance the attractiveness of different blend ratios of sex lures. Olfactometer bioassays showed that males prefer volatiles emitted from different combinations of castor bean plant extracts and a signaling female over a female alone. In the presence of castor bean plants copulation rates of H. parallela were highest among all test environments both in laboratory bioassays (60%) and in field tests (70%). This study, combined with our previous observation of the feeding behavior of H. parallela adults on castor bean leaves, suggests that castor bean plants may provide an attractive but risky mating site for H. parallela beetles. The enhancement of male mate-location and copulation rate in the presence of castor bean plants can balance its paralytic effects on H. parallela after intake of potential toxins contained in its leaves.     

Nocturnal Plant Bugs Use <Emphasis Type="Italic">cis</Emphasis>-Jasmone to Locate Inflorescences of an Araceae as Feeding and Mating Site

Inflorescences of Araceae pollinated by cyclocephaline scarab beetles are visited frequently by a wide array of other arthropods that exploit floral resources without taking part in pollination, including earwigs, flies, and true bugs. To date, nothing is known about the cues these insect visitors use to locate the inflorescences and whether or to what extent floral scents play a role. An aroid visited by large numbers of plant bugs (Miridae) in addition to cyclocephaline scarab beetle pollinators is the Neotropical species Dieffenbachia aurantiaca. We identified the plant bug species and investigated their behavior and arrival time on the inflorescences. To test the importance of olfactory cues in locating their host we conducted experiments with open and gauze-bagged inflorescences as well as natural scent samples of D. aurantiaca. Inflorescence scents were analyzed by gas chromatography linked to mass spectrometry (GC/MS), and the attractive potential of the main scent compound was determined by behavioral assays. Three species of Neella, the most common one being N. floridula, visited the inflorescences at nightfall, shortly after the beginning of scent emission, and showed feeding and copulation activity. Bagged inflorescences as well as natural scent samples attracted similar numbers of plant bugs as the non-bagged inflorescences, showing that olfactory cues are sufficient for them to locate their host. Cis-jasmone was the major component within the inflorescence scent bouquet. In two-choice field bioassays, this compound proved to be highly attractive to Neella, and thus obviously plays a key role in finding host plants.     

Role of Plant Volatiles in Host Plant Recognition by <Emphasis Type="Italic">Listronotus maculicollis</Emphasis> (Coleoptera: Curculionidae)

The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby, is an economically important pest of short cut turfgrass. Annual bluegrass, Poa annua L., is the most preferred and suitable host for ABW oviposition, larval survival and development. We investigated the involvement of grass volatiles in ABW host plant preference under laboratory and field conditions. First, ovipositional and feeding preferences of ABW adults were studied in a sensory deprivation experiment. Clear evidence of involvement of olfaction in host recognition by ABW was demonstrated. Poa annua was preferred for oviposition over three bentgrasses, Agrostis spp., but weevils with blocked antennae did not exhibit significant preferences. ABW behavioral responses to volatiles emitted by Agrostis spp. and P. annua were examined in Y-tube olfactometer assays. Poa annua was attractive to ABW females and preferred to Agrostis spp. cultivars in Y-tube assays. Headspace volatiles emitted by P. annua and four cultivars of Agrostis stolonifera L. and two each of A. capillaris L. and A. canina L. were extracted, identified and compared. No P. annua specific volatiles were found, but Agrostis spp. tended to have larger quantities of terpenoids than P. annua. (Z)-3-hexenyl acetate, phenyl ethyl alcohol and their combination were the most attractive compounds to ABW females in laboratory Y-tube assays. The combination of these compounds as a trap bait in field experiments attracted adults during the spring migration, but was ineffective once the adults were on the short-mown turfgrass. Hence, their usefulness for monitoring weevil populations needs further investigation.     

Electrophysiological and behavioral responses of female African rice gall midge, <Emphasis Type="Italic">Orseolia oryzivora</Emphasis> Harris and Gagné, to host plant volatiles

African rice gall midge, Orseolia oryzivora Harris and Gagné, is a major pest of rice in Africa. Depsite its economic importance, its chemical ecology is not well understood. Here, we assessed behavioral and electrophysiological responses of O. oryzivora to host plant volatiles. In olfactometer bioassays, mated female O. oryzivora were attracted to volatiles emitted from intact rice plants but were repelled by volatiles collected from plants infested by conspecifics. In a choice test, there was a preference for volatiles from uninfested plants over those from infested plants. Coupled gas chromatography-electroantennography analyses of panicle volatiles isolated four electrophysiologically active components: (S)-linalool, 4,8-dimethyl-1,3,7-nonatriene, (E)-caryophyllene, and (R/S)-(E)-nerolidol. A synthetic blend of volatiles at the same concentration and ratio as that from an intact plant was attractive to mated females, whereas a blend based on the ratio of volatiles from an infested plant was repellent. This suggests that O. oryzivora uses olfaction for host plant recognition. The identification of blends of volatiles emitted by plants that can both attract and repel O. oryzivora may aid the development of sustainable control measures.     

Attractiveness of Host Plant Volatile Extracts to the Asian Citrus Psyllid, <Emphasis Type="Italic">Diaphorina citri,</Emphasis> is Reduced by Terpenoids from the Non-Host Cashew

Diaphorina citri is a vector of the bacterial causative agent of Huanglongbing (HLB?=?Citrus greening), a severe disease affecting citrus crops. As there is no known control for HLB, manipulating insect behaviour through deployment of semiochemicals offers a promising opportunity for protecting citrus crops. The behavioural responses of D. citri to plant volatiles, and the identity of these plant volatiles were investigated. Volatiles were collected from host plants Murraya paniculata, Citrus sinensis, C. reshni, C. limettioides, Poncirus trifoliata, and from non-host plants Psidium guajava, Mangifera indica, Anacardium occidentale. In behavioural assays, female D. citri spent more time in the arms containing volatiles from either M. paniculata or C. sinensis compared to the control arms. When D. citri was exposed to volatiles collected from A. occidentale, they preferred the control arm. Volatiles emitted from the other studied plants did not influence the foraging behaviour of D. citri. Chemical analyses of volatile extracts from C. sinensis, M. paniculata, and A. occidentale revealed the presence of the terpenoids (E)-4,8-dimethylnona-1,3,7–triene (DMNT) and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT) in higher amounts in A. occidentale. In further behavioural bioassays, female D. citri spent less time in arms containing a synthetic blend of DMNT and TMTT compared to the control arms. Female D. citri also spent less time in arms containing the synthetic blend in combination with volatile extracts from either M. paniculata or C. sinensis compared to the control arms. Results suggest that higher release of the two terpenoids by A. occidentale make this species unattractive to D. citri, and that the terpenoids could be used in reducing colonisation of citrus plants and therefore HLB infection.     

Qualitative and Quantitative Differences in Herbivore-Induced Plant Volatile Blends from Tomato Plants Infested by Either <Emphasis Type="Italic">Tuta absoluta</Emphasis> or <Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Plants release a variety of volatile organic compounds that play multiple roles in the interactions with other plants and animals. Natural enemies of plant-feeding insects use these volatiles as cues to find their prey or host. Here, we report differences between the volatile blends of tomato plants infested with the whitefly Bemisia tabaci or the tomato borer Tuta absoluta. We compared the volatile emission of: (1) clean tomato plants; (2) tomato plants infested with T. absoluta larvae; and (3) tomato plants infested with B. tabaci adults, nymphs, and eggs. A total of 80 volatiles were recorded of which 10 occurred consistently only in the headspace of T. absoluta-infested plants. Many of the compounds detected in the headspace of the two herbivory treatments were emitted at different rates. Plants damaged by T. absoluta emitted at least 10 times higher levels of many compounds compared to plants damaged by B. tabaci and intact plants. The multivariate separation of T. absoluta-infested plants from those infested with B. tabaci was due largely to the chorismate-derived compounds as well as volatile metabolites of C₁₈-fatty acids and branched chain amino acids that had higher emission rates from T. absoluta-infested plants, whereas the cyclic sesquiterpenes α- and β-copaene, valencene, and aristolochene were emitted at significantly higher levels from B. tabaci-infested plants. Our findings imply that feeding by T. absoluta and B. tabaci induced emission of volatile blends that differ quantitatively and qualitatively, providing a chemical basis for the recently documented behavioral discrimination by two generalist predatory mirid species, natural enemies of T. absoluta and B. tabaci employed in biological control.     

The Aggregation Pheromone of <Emphasis Type="Italic">Phyllotreta striolata</Emphasis> (Coleoptera: Chrysomelidae) Revisited

Aggregations of the striped flea beetle Phyllotreta striolata on their crucifer host plants are mediated by volatiles emitted from feeding males. The male-specific sesquiterpene, (6R,7S)-himachala-9,11-diene (compound A), was shown previously to be physiologically and behaviorally active, but compound A was attractive only when combined with unnaturally high doses of the host plant volatile allyl isothiocyanate (AITC) in field trapping experiments. This indicated that our understanding of the chemical communication in this species is incomplete. Another male-specific sesquiterpenoid, (3S,9R,9aS)-3-hydroxy-3,5,5,9-tetramethyl-5,6,7,8,9,9a-hexahydro-1H-benzo[7]annulen-2(3H)-one (compound G), has been reported from an American P. striolata population. We confirmed the presence of compound G, and investigated its interaction with compound A and AITC in a P. striolata population in Taiwan. Compound G was attractive to Taiwanese P. striolata in laboratory bioassays, but significantly more beetles were attracted to a blend of compounds A and G. Under the same conditions, P. striolata showed no preference for the blend of A and G combined with a range of doses of AITC over the sesquiterpenoid blend alone. The sesquiterpenoid blend was tested further in field trapping experiments and attracted significantly more beetles than traps baited with compound A and ecologically relevant amounts of AITC. We conclude that A and G are components of the male-specific aggregation pheromone of P. striolata in Taiwan, and that the attractiveness of the pheromone is not reliant on the presence of AITC. Our results further indicate that the male-specific sesquiterpenoid blends differ qualitatively between the Taiwanese and American populations of P. striolata.     

(<Emphasis Type="Italic">Z</Emphasis>)-7-Hexadecene is an Aggregation-Sex Pheromone Produced by Males of the South American Cerambycid Beetle <Emphasis Type="Italic">Susuacanga octoguttata</Emphasis>

We describe the identification, synthesis, and field bioassays of a novel aggregation-sex pheromone produced by males of Susuacanga octoguttata (Germar), a South American cerambycid beetle. Analyses of extracts of headspace volatiles produced by adult beetles revealed a sex-specific compound emitted by males which was identified as (Z)-7-hexadecene by microchemical and spectroscopic analyses. The synthesized pheromone was attractive to beetles of both sexes in field trials. This unsaturated hydrocarbon motif is unprecedented among cerambycid pheromones identified to date. During field bioassays, we serendipitously discovered that adults of S. octoguttata trapped in two Brazilian biomes differed considerably in elytral markings, although males from both populations produced (Z)-7-hexadecene as an aggregation-sex pheromone.     

Responses of Parasitoids to Volatiles Induced by <Emphasis Type="Italic">Chilo partellus</Emphasis> Oviposition on Teosinte,a Wild Ancestor of Maize

Maize, a genetically diverse crop, is the domesticated descendent of its wild ancestor, teosinte. Recently, we have shown that certain maize landraces possess a valuable indirect defense trait not present in commercial hybrids. Plants of these landraces release herbivore-induced plant volatiles (HIPVs) that attract both egg [Trichogramma bournieri Pintureau & Babault (Hymenoptera: Trichogrammatidae)] and larval [Cotesia sesamiae Cameron (Hymenoptera: Braconidae)] parasitoids in response to stemborer egg deposition. In this study, we tested whether this trait also exists in the germplasm of wild Zea species. Headspace samples were collected from plants exposed to egg deposition by Chilo partellus Swinhoe (Lepidoptera: Crambidae) moths and unexposed control plants. Four-arm olfactometer bioassays with parasitic wasps, T. bournieri and C. sesamiae, indicated that both egg and larval parasitoids preferred HIPVs from plants with eggs in four of the five teosinte species sampled. Headspace samples from oviposited plants released higher amounts of EAG-active compounds such as (E)-4,8-dimethyl-1,3,7-nonatriene. In oviposition choice bioassays, plants without eggs were significantly preferred for subsequent oviposition by moths compared to plants with prior oviposition. These results suggest that this induced indirect defence trait is not limited to landraces but occurs in wild Zea species and appears to be an ancestral trait. Hence, these species possess a valuable trait that could be introgressed into domesticated maize lines to provide indirect defense mechanisms against stemborers.     

Behavioral Evidence for Olfactory-Based Location of Honeybee Colonies by the Scarab <Emphasis Type="Italic">Oplostomus haroldi</Emphasis>

The Afro-tropical scarab Oplostomus haroldi (Witte) is a pest of honeybees in East Africa with little information available on its chemical ecology. Recently, we identified a female-produced contact sex pheromone, (Z)-9-pentacosene, from the cuticular lipids that attracted males. Here, we investigated the kairomonal basis of host location in O. haroldi. We used coupled gas chromatography/electroantennographic detection (GC/EAD) and GC/mass spectrometry to identify antennally-active compounds from volatiles collected from honeybee colonies. Antennae of both sexes of the beetle consistently detected seven components, which were identified as 3-hydroxy-2-butanone, 2,3-butanediol, butyl acetate, isopentyl acetate, butyl butyrate, hexyl acetate, and methyl benzoate. In olfactometer bioassays, both sexes responded to the full seven-component synthetic blend over solvent controls, but chose honeybee colony odors over the blend. These findings suggest that the seven compounds are components of a kairomone from honeybee colonies used by O. haroldi.     

Feeding Experience Affects the Behavioral Response of Polyphagous Gypsy Moth Caterpillars to Herbivore-induced Poplar Volatiles

Plant volatiles influence host selection of herbivorous insects. Since volatiles often vary in space and time, herbivores (especially polyphagous ones) may be able to use these compounds as cues to track variation in host plant quality based on their innate abilities and previous experience. We investigated the behavioral response of naïve (fed on artificial diet) and experienced (fed on poplar) gypsy moth (Lymantria dispar) caterpillars, a polyphagous species, towards constitutive and herbivore-induced black poplar (Populus nigra) volatiles at different stages of herbivore attack. In Y-tube olfactometer assays, both naïve and experienced caterpillars were attracted to constitutive volatiles and volatiles released after short-term herbivory (up to 6 hr). Naïve caterpillars also were attracted to volatiles released after longer-term herbivory (24–30 hr), but experienced caterpillars preferred the odor of undamaged foliage. A multivariate statistical analysis comparing the volatile emission of undamaged plants vs. plants after short and longer-term herbivory, suggested various compounds as being responsible for distinguishing between the odors of these plants. Ten compounds were selected for individual testing of caterpillar behavioral responses in a four-arm olfactometer. Naïve caterpillars spent more time in arms containing (Z)-3-hexenol and (Z)-3-hexenyl acetate than in solvent permeated arms, while avoiding benzyl cyanide and salicyl aldehyde. Experienced caterpillars avoided benzyl cyanide and preferred (Z)-3-hexenyl acetate and the homoterpene (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) over solvent. Only responses to DMNT were significantly different when comparing experienced and naïve caterpillars. The results show that gypsy moth caterpillars display an innate behavioral response towards constitutive and herbivore-induced plant volatiles, but also that larval behavior is plastic and can be modulated by previous feeding experience.