Multifunctional communication inRiptortus clavatus (Heteroptera: Alydidae): Conspecific nymphs and egg parasitoidOoencyrtus nezarae use the same adult attractant pheromone as chemical cue

The bean bug,Riptortus clavatus lays scattered eggs (as opposed to the egg masses of pentatomids) on host as well as nonhost plants. Therefore, the first feeding stage (second-instar) nymphs emerging from eggs laid on nonhost plants need a signal that enables them to locate a food source at the lowest energy cost. Male-released (E)-2-hexenyl (E)-2-hexenoate, (E)-2-hexenyl (Z)-3-hexenoate, and myristyl isobutyrate play the double role of attractant pheromone for adults as well as aggregation pheromone, which enables the second-instar nymphs to find the host food plant. These male-specific semiochemicals are released only when foodstuff is available. On the other hand, females ofOoencyrtus nezarae, the most effective parasitoid of the host in Kumamoto, Japan (where the field experiments were conducted), utilize these semiochemicals as kairomones in order to locate the potential host community. Field experiments revealed that the synthetic pheromone rivaled 10 live males in the attraction of adults and second-instar nymphs. Captures of the egg parasitoidO. nezarae females in cylindrical sticky traps were significantly higher in traps baited with the synthetic semiochemicals than in control traps. The number of females captured was significantly higher than the number of males, although the captures in the sticky suction trap system revealed that the populations of male and female were not significantly different.     

Interspecific Pheromone Cross-Attraction Among Soybean Bugs (Heteroptera): Does Piezodorus hybneri (Pentatomidae) Utilize the Pheromone of Riptortus clavatus (Alydidae) as a Kairomone?

The chemical and ecological function of cross-attraction of Piezodorus hybneri (Pentatomidae) to the Riptortus clavatus (Alydidae) pheromone (a mixture of three components) was studied. In a field attraction test using traps with synthetic pheromone components, P. hybneri was attracted to (E)-2-hexenyl (E)-2-hexenoate, a component of the R. clavatus pheromone. Other components had neither an additive nor a synergistic effect on the attraction of P. hybneri. Neither (E)-2-hexenyl (E)-2-hexenoate nor other components of the R. clavatus pheromone were detected in volatiles or whole-body extracts of P. hybneri adults by gas chromatographic analysis. In addition, (E)-2-hexenyl (E)-2-hexenoate could not be found in volatiles of soybean plants. Therefore, it appears that P. hybneri responds to a component of the R. clavatus pheromone that is not emitted by P. hybneri itself. We discuss this interspecific pheromone cross-attraction of the soybean bug and hypothesize that P. hybneri utilizes the pheromone of its competitor as a kairomone for host location.     

Female-Produced Sex Pheromone of the Predatory Bug Geocoris punctipes

A compound identified from air-entrained volatiles produced by adult female Geocoris punctipes attracted male bugs and stimulated males to investigate nearby moving objects of the appropriate size in their search for females. The compound was identified as (E)-2-octenyl acetate, a relatively common component of the volatile semiochemicals produced by a number of heteropteran species. This compound comprised a significant proportion of the female volatiles, whereas it was detected in only trace amounts in volatiles collected from live males. Other components in the extracts from adults of both sexes included (E)-2-hexenyl acetate, (E)-2-octenal, and several saturated hydrocarbons, but these components were not part of the attractant. These compounds plus (E)-2-hexenal, (E)-4-oxo-2-hexenal, and (E)-2-decenal were found in extracts of homogenized adults, whereas the cast skins from late instar nymphs contained (E)-2-octenal, (E)-4-oxo-2-octenal, (E)-2-octenoic acid, and several saturated hydrocarbons.     

Alarm Pheromone System of the Western Conifer Seed Bug, Leptoglossus occidentalis

The alarm pheromones for adult and nymphal western conifer seed bugs, Leptoglossus occidentalis, were collected from the headspace volatiles of agitated bugs and from extracted adult thoraxes and nymphal abdomens. Adult bugs secreted a blend from the metathoracic glands that consisted of hexyl acetate, hexanal, hexanol, heptyl acetate, and octyl acetate (ratio of 152:103:8:1.5:1). Nymphal alarm pheromone produced by the dorsal abdominal glands consisted of (E)-2-hexenal. Agitated adults emitted 24% of the pheromone contained within the glands, while nymphs released 33% of their constitutive supply. The complete blend from both adults and nymphs, tested in a laboratory headspace bioassay, elicited a dispersal (or alarm) response in >70% of individuals tested. Nymphs in the field exposed to synthetic adult or nymphal pheromones, or a mixture of both, responded with >50% dispersing. When single components were tested on adults reared under summer conditions in a forced-air one-way bioassay, hexanal and hexyl acetate, the major components of the secretion, were responsible for eliciting the alarm response. Adults collected in the fall from the field were unresponsive to the tested blend, suggesting that adults seeking aggregation sites in the fall become refractory to alarm pheromone stimuli that would cause aggregations to disperse. The weak dispersal responses elicited in both adults and nymphs by either nymphal or adult pheromones are consistent with a tradeoff in the advantage gained by avoiding predation and the disadvantage of leaving a food source. Because of these weak responses, use of alarm pheromones as pest management tools against L. occidentalis is unlikely.     

Evidence for mediation of two releaser pheromones in the aggregation behavior of the gregarious desert locust,Schistocerca gregaria (forskal) (Orthoptera: Acrididae)

The response of nymphal and adult gregarious phase desert locust,Schistocerca gregaria, to a choice of two columns of air, one permeated with airborne volatiles emanating from nymphs or adults and the other untreated, was investigated in a single-chamber bioassay arena. The nymphs, whether released individually or in groups, preferred to be within the precinct of the air column treated with airborne volatiles of the nymphs but were indifferent to volatiles of the adults. Conversely, older adults responded only to their own volatiles but not to those of the nymphs or young adults. The young adults were responsive only to volatiles of the older adults. Charcoal-trapped volatiles from the nymphs and the adults reproduced the effect of living locusts. These results indicate that there are two different aggregation pheromones inS. gregaria: a juvenile pheromone produced by nymphs and an adult pheromone specific to adults.     

Sex pheromone of oriental beetle,Exomala orientalis: Identification and field evaluation

A gas chromatograph coupled with a behavioral bioassay was used to identify two sex pheromone components, 7-(Z)- and 7-(E)-tetradecen-2-one of the Oriental beetle (OB),Exomala orientalis. Field experiments showed that the blend of the two isomers (Z:E, 7:1) was not significantly more attractive than theZ component alone. The best performance of traps baited with the synthetic sex pheromone was achieved when they were set with the pheromone device at 30 cm above the ground. Catches in traps baited with 1 and 10 mg were not significantly different, but they were higher (2.9-fold) than captures in traps loaded with 0.1 mg of the pheromone. Further investigations by GC-EAD revealed the presence of a possible minor component, but the small amount of material prevented its identification. 2-(E)-Nonenol, with the same retention time as the natural product, did not affect the attractancy of the synthetic sex pheromone. GC-EAD screening of previously identified sex pheromones of scarab beetles showed that male antennae of the Oriental beetle responded to japonilure, but it showed neither synergism nor inhibition to the OB sex pheromone.     

(<Emphasis Type="Italic">E,E</Emphasis>)-α-Farnesene,an Alarm Pheromone of the Termite <Emphasis Type="Italic">Prorhinotermes canalifrons</Emphasis>

The behavioral and electroantennographic responses of Prorhinotermes canalifrons to its soldier frontal gland secretion, and two separated major components of the secretion, (E)-1-nitropentadec-1-ene and (E,E)-α-farnesene, were studied in laboratory experiments. Behavioral experiments showed that both the frontal gland secretion and (E,E)-α-farnesene triggered alarm reactions in P. canalifrons, whereas (E)-1-nitropentadec-1-ene did not affect the behavior of termite groups. The alarm reactions were characterized by rapid walking of activated termites and efforts to alert and activate other members of the group. Behavioral responses to alarm pheromone differed between homogeneous and mixed groups, suggesting complex interactions. Antennae of both soldiers and pseudergates were sensitive to the frontal gland secretion and to (E,E)-α-farnesene, but soldiers showed stronger responses. The dose responses to (E,E)-α-farnesene were identical for both soldiers and pseudergates, suggesting that both castes use similar receptors to perceive (E,E)-α-farnesene. Our data confirm (E,E)-α-farnesene as an alarm pheromone of P. canalifrons.     

The Nasonov pheromone of the honeybeeApis mellifera L. (Hymenoptera,Apidae). Part II. Bioassay of the components using foragers

The Nasonov pheromone of the honeybee comprises seven components, (Z)-citral, nerol, geraniol, nerolic acid, geranic acid, and (E,E)-farnesol. Bioassay of individual components showed each attracted foraging bees. A mixture of components in proportions present in the honeybee was as attractive as the natural secretion, and each component contributed to the attractiveness of the mixture. Honeybees responded anemotactically to the source of Nasonov odor. The presence of footprint pheromone enhanced the attractiveness of the synthetic Nasonov mixture. Nasonov and footprint pheromones may prove useful in attracting honeybees to crops needing pollination.     

Fecal volatiles as part of the aggregation pheromone complex of the desert locust,Schistocerca gregaria (Forskal) (Orthoptera: Acrididae)

Olfactometric bioassays showed that nymphs of crowded desert locusts,Schistocerca gregaria, aggregated in response to volatiles derived from their feces and to volatiles emitted from the feces of young adults, but were indifferent to volatiles emitted by older adult feces. On the other hand, young and older adults were not only responsive to their own fecal volatiles but also cross-responsive to each other's and that of the nymphs. Charcoal-trapped volatiles from the feces and synthetic blends of the fecal volatiles also elicited similar responses. Young adults responded moderately to a blend of nymphal volatiles and those derived from nymphal feces. GC-EAD and GC-MS analysis of the trapped volatiles revealed the presence of guaiacol and phenol as predominant electrophysiologically active components of nymphal and young adult feces. Fecal volatiles of older adult contained phenylacetonitrile in addition to guaiacol and phenol, which were present in relatively lower proportion. These results suggest that fecal volatiles are part of the aggregation pheromone complex of the desert locust, which includes the pheromone blends produced by nymphs and older adults, respectively.     

Attraction of Piezodorus hybneri to the Aggregation Pheromone Components of Riptortus clavatus

The aggregation pheromone of Riptortus clavatus (Heteroptera: Alydidae) consists of (E)-2-hexenyl (Z)-3-hexenoate (E2HZ3H), (E)-2-hexenyl (E)-2-hexenoate (E2HE2H), and myristyl isobutyrate (MI). Experiments were conducted to examine the attraction of Piezodorus hybneri (Heteroptera: Pentatomidae) to the pheromone components of R. clavatus, individually and in combination, and to determine if P. hybneri produces these compounds. Electroantennogram (EAG) responses of P. hybneri to E2HE2H were significant in a dose dependent manner, while those to E2HZ3H were not significantly different from those to hexane and air. Field trapping tests using E2HZ3H, E2HE2H, and MI, individually or in combination, showed that only E2HE2H was attractive to P. hybneri. E2HE2H was not detected in whole-body extracts or volatile collections from either sex of P. hybneri adults. We propose that the response of P. hybneri adults to the R. clavatus aggregation pheromone may be related to finding suitable host plants.     

Olfactory Reception of Conspecific Aggregation Pheromone and Plant Odors by Nymphs of the Predator, Podisus maculiventris

Olfactory reception of 23 odorants, including plant volatiles and male-produced aggregation pheromone, by third and fifth instars of the spined soldier bug (SSB) Podisus maculiventris was investigated by using electroantennograms (EAGs). Both nymphal stages were sensitive to male-produced aggregation pheromone components (E)-2-hexenal, benzyl alcohol, and -terpineol. The plant volatile, (E)-2-hexen-1-ol (a chemical known to be released by plants in response to prey feeding over the short-term), elicited the largest EAGs of all volatiles tested. While third instars were sensitive to nonanal, only fifth instars responded to both nonanal and (±)-linalool, both compounds released systemically by plants in response to feeding by potential prey. Antennal extirpation experiments showed that sensilla responsive to hexan-1-ol, (E)-2-hexenal, and -terpineol are situated mainly on the terminal antennal segment. The results support the hypothesis that P. maculiventris nymphs use both plant volatiles and pheromone components in locating potential prey and other behaviors.     

Beyond 9-ODA: SEX Pheromone Communication in the European Honey Bee Apis mellifera L.

The major component of the mandibular gland secretion of queen honeybees (Apis mellifera L.), 9-ODA ((2E)-9-oxodecenoic acid), has been known for more than 40 yr to function as a long-range sex pheromone, attracting drones at congregation areas and drone flyways. Tests of other mandibular gland components failed to demonstrate attraction. It remained unclear whether these components served any function in mating behavior. We performed dual-choice experiments, using a rotating drone carousel, to test the attractiveness of 9-ODA compared to mixtures of 9-ODA with three other most abundant components in virgin queen mandibular gland secretions: (2E)-9-hydroxydecenoic acid (9-HDA), (2E)-10-hydroxydecenoic acid (10-HDA), and p-hydroxybenzoate (HOB). We found no differences in the number of drones attracted to 9-ODA or the respective mixtures over a distance. However, adding 9-HDA and 10-HDA, or 9-HDA, 10-HDA, and HOB to 9-ODA increased the number of drones making contact with the baited dummy. On the basis of these results, we suggest that at least 9-HDA and 10-HDA are additional components of the sex pheromone blend of A. mellifera.     

Semiochemical-mediated flight responses of sap beetle vectors of oak wilt,Ceratocystis fagacearum

The sap beetle, Colopterus truncatus (Coleoptera: Nitidulidae), is one of the primary vectors of the oak wilt pathogen, Ceratocystis fagacearum, in the north-central United States. Field behavioral assays utilizing various release rates and blends of three methyl-branched hydrocarbon aggregation pheromone components showed that flight responses of this beetle were similar in Illinois and Minnesota populations. In both locations, both sexes of the beetle responded synergistically to a combination of the three-component pheromone and fermenting whole-wheat bread dough. Further, Colopterus truncatus preferred a high release rate over a low release rate of the three-component blend. In both locations, the response of C. truncatus to a simplified version of the pheromone consisting of (2E,4E,6E)-3,5-dimethyl-2,4,6-octatriene (1) and (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6,8-decatetraene (3) was not significantly different from the response to the three-component blend. An experiment in Illinois with all possible combinations of the components demonstrated that the decatetraene (3) was the crucial component in the blend; of all treatments, the maximal response was elicited by 3 + dough. Chipped bark, phloem, and xylem from northern pin oak, Quercus ellipsoidalis, was not attractive to C. truncatus in Minnesota. During a weekly survey over two seasons in Minnesota, C. truncatus flew in response to the three-component pheromone between early April and early July, with the maximum responses coming on May 4, 2000 and April 20, 2001. During both years, more than 98% of the beetles were trapped between April 14 and June 1. During the same survey, Glischrochilus spp. (Nitidulidae) flew during longer periods of the summer, particularly in 2001. The sex ratio of C. truncatus responding during all experiments was female-biased (1.8:1, female–male), which is characteristic of other male-produced coleopteran aggregation pheromones. Other sap beetles that play a minor role in the pathobiology of C. fagacearum also responded in experiments conducted in Minnesota. Carpophilus brachypterus Say was cross-attracted to the two- and three-component blends of the C. truncatus pheromone and dough, whereas two Glischrochilus spp. were attracted to all treatments that contained dough.     

Reinvestigation confirms action of Δ11-desaturases in spruce budworm moth sex pheromone biosynthesis

The biosynthesis of a large number of sex pheromone components of various moth species has been shown to start with common fatty acids and involve chain shortening by two carbons and introduction of a double bond at the 11–12 position. A recent report indicates that one of these common components, (E)-11-tetradecenyl acetate, is present in the eastern spruce budworm,Choristoneurafumiferana, but is not made by this pathway. Reinvestigation of this insect using in vivo and in vitro techniques indicates that the acetate indeed is made by a sequence of reactions similar to that used in other leafroller moths. In fact, evidence was found for the presence of several 11-desaturase systems in spruce budworm. One produced a large quantity of (Z)-11-hexadecanoic acid, and another produced (E)-11-tetradecanoic acid. It is not known if the small amount of (Z)-11-tetradecanoic acid is produced by either of those two systems or by a third system. A comparison with other species showed that cabbage looper moths have only the first system, redbanded leafroller moths use the last two systems, and European corn borer moths have all three.     

Male-Produced Aggregation Pheromone of the Cerambycid Beetle <Emphasis Type="Italic">Rosalia funebris</Emphasis>

We report the identification, synthesis, and field bioassays of a volatile, male-produced aggregation pheromone of a long-horned beetle, the banded alder borer, Rosalia funebris Mots. Headspace collections from males contained a major male-specific compound, (Z)-3-decenyl (E)-2-hexenoate, and several minor components, identified as (Z)-3-decenol, (Z)-3-nonenyl (E)-2-hexenoate, and (Z)-3-decenyl (E)-3-hexenoate. The antennae of both males and females responded strongly to (Z)-3-decenyl (E)-2-hexenoate. We collected significant numbers of adult R. funebris in field bioassays using traps baited with this compound. This pheromone structure is unprecedented in the literature of cerambycid pheromones and distinct from the more common diol/hydroxyketone pheromone motif of many other species of the diverse subfamily Cerambycinae. This is the first pheromone identified for a species in the tribe Rosaliini. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Identification and bioactivity of alarm pheromone in the western flower thrips,Frankliniella occidentalis

Analysis by gas chromatography (GC) and GC-mass spectroscopy disclosed that droplets of anal fluid produced by second-instar western flower thrips,Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), contain a two-component alarm pheromone, comprised of decyl acetate and dodecyl acetate, in a molar ratio of approximately 1.51. Both nymphs and adults responded to the pheromone by walking away from the source. The synthetic pheromone was active at a concentration of 1.0 ng, and the proportions of insects responding to the pheromone, but not the distances moved, increased with increasing dose. Each component was active alone, although at low doses, the response to decyl acetate was less than to either dodecyl acetate or the blend. The pheromone also induced some second instars to drop from leaves and reduced oviposition by adult females in both two-choice and nochoice experiments. Because the response of western flower thrips to the alarm pheromone is relatively weak, the potential for its use in pest management is limited, unless it is used in conjunction with other control measures.     

Evidence of an Assembly Pheromone in the Black-Legged Deer Tick, Ixodes scapularis

The responses of scapularis (Acari: Ixodidae) nymphs and adults to extracts of cast larval skins were tested in a Petri dish bioassay. Assembly was elicited in nymphs and adults in the presence of skins, exudate from ticks, and filter paper exposed to ticks compared to untreated controls. Assembly was noted by 1 hr after exposure with little change between 1 and 24 hr. The assembly response increased in the presence of an increased number of skins. Similar assembly was elicited in nymphs and adults in the presence of cast larval skins and a saline (0.95% NaCl) skin extract. Methanol and hexane extracts were not attractive. When chemical standards were tested against nymphs, they responded to guanine, uric acid, hypoxanthine, xanthine, inosine, and hematin. Adults were tested against guanine, inosine, and xanthine, and all elicited significant assembly. Responses of nymphs increased significantly with increase in dose of uric acid and guanine. Responses of nymphs to a mixture of guanine, xanthine, and adenine (25:1:1 ratio) were similar to responses to cast skins. This study provides the first evidence of an assembly pheromone in I. scapularis.     

Decadienoates: Sex Pheromone Components of Nettle Caterpillars Darna trima and D. bradleyi

This study was undertaken to identify sex pheromone components of nettle caterpillars Darna trima and Darna bradleyi (Lepidoptera: Limacodidae) whose larvae defoliate oil palm, Elaeis guineensis, in southeast Asia. Coupled gas chromatographic–electroantennographic detection (GCEAD) analyses of pheromone gland extracts revealed two antennally active compounds produced by female D. trima and two by female D. bradleyi. Molecular structures of these candidate pheromone components were identified by electron-impact and chemical-ionization mass spectrometry; retention-index calculations on DB-5, DB-23, and DB-210 columns; microanalytical treatments, as well as syntheses of "auxilliary" compounds that facilitated identification of the compounds. The compounds from D. trima were 2-methylbutyl (E)-7,9-decadienoate (A) and (E)-2-hexenyl (E)-7,9decadienoate (B); from D. bradleyi we identified methyl (E)-7,9-decadienoate (C), and isobutyl (E)-7,9-decadienoate (D). In field experiments in Malaysia, (S)-2-methylbutyl (E)-7,9-decadienoate (SA) in combination with B proved to be essential and synergistic pheromone components for attraction of male D. trima. (R)-2-Methylbutyl (E)-7,9-decadienoate (RA) had no behavioral activity. Compound D singly attracted male D. bradleyi, but addition of C to D at a 1 : 10 ratio significantly enhanced attractiveness of the bait. Synthetic pheromone blends were more effective trap baits than unmated female moths and could be developed for monitoring populations of D. trima and D. bradleyi in Asian oil palm plantations.     

Intra- and Interspecific Aggregation Responses of Locusta migratoria migratorioides and Schistocerca gregaria and a Comparison of Their Pheromone Emissions

Gregarious nymphs of Schistocerca gregaria and Locusta migratoria migratorioides are often seen to march together in common bands in the field. In the present study, the intraspecific aggregation responses of nymphal and older stages of the two insects were compared with their interspecific responses. Unlike S. gregaria, L. m. migratorioides shows a lesser pattern of stage and sex differentiation in its aggregation pheromone biology. Thus, although fifth-instar nymphs did not respond significantly to the adult pheromone, adults responded significantly to the nymph pheromone. No cross-stage aggregative responses occur in S. gregaria. In the adults of S. gregaria, production of the pheromone is male-specific; in L. m. migratorioides both sexes induced a significant level of aggregation from conspecifics. Aggregation assays between corresponding stages of the two species showed stronger interaction between the nymphal stages than between the adults and account for the frequent occurrence of mixed hopper bands in the field. GC-EAD studies of volatiles of nymphal and adult stages by using antennal preparations from both species also showed significant interspecies reactivities. GC-MS analyses showed that of S. gregaria nymphal pheromone components (C₆ and C₈ to C₁₀ straight-chained aldehydes and acids and the fecal phenols, guaiacol and phenol), the acids and phenols constitute the common components of nymphal stages. Phenylacetonitrile, the major component of S. gregaria adult aggregation pheromone, is present in L. m. migratorioides nymphal volatiles, albeit at a lower level. Unlike S. gregaria adult pheromone blend, which is made up wholly of benzene derivatives, the volatile emissions of L. m. migratorioides adults is dominated by aliphatic aldehydes and alcohols. The possible role of cross-aggregation effects in mutually facilitating phase transformation of the two species is discussed.     

Response of The Lacewing Chrysopa cognata to Pheromones of its Aphid Prey

The lacewing Chrysopa cognata, one of the principal predators of aphids in Korea, was tested for responses to the aphid sex pheromone components (4aS,7S,7aR)-nepetalactone and (1R,4aS,7S,7aR)-nepetalactol and the aphid alarm pheromone (E)--farnesene. Electroantennogram responses were obtained to the sex pheromone components but not to (E)--farnesene. The sex pheromone components were attractive in a Y-tube olfactometer assay and in field trials with water traps, but no attraction was observed to (E)--farnesene.