Pharmacophagy of Methyl Eugenol by Males Enhances Sexual Selection of <Emphasis Type="Italic">Bactrocera carambolae</Emphasis>

After pharmacophagy of methyl eugenol (ME), males of Bactrocera carambolae (Diptera: Tephritidae) produced (E)-coniferyl alcohol (CF) along with its endogenously synthesized pheromonal compounds. CF was shown to be released into the air by the ME-fed males only during the courtship period at dusk and attracted significantly more males and females than the ME-deprived males in wind tunnel assays. However, earlier onset of sexual attraction and a higher mating success were observed only in the wind tunnel and field cage assays on the third day posttreatment of ME. Field cage observations on the male-to-male interaction indicated that the ME-deprived males did not exhibit aggregation behavior, but that ME feeding promoted aggregation behavior in B. carambolae. Field cage observations revealed that the ME-deprived males were not only attracted to the ME-fed males, but also appeared to feed on their anal secretions. The secretions were subsequently confirmed to contain CF along with endogenously produced pheromonal compounds. Results obtained for B. carambolae were compared to those previously obtained from its sibling species, Bactrocera dorsalis, and are discussed in light of species advancement in fruit fly–plant relationships.     

Floral synomone of a wild orchid,Bulbophyllum cheiri,lures Bactrocera fruit flies for pollination

The major fruit fly attractant component in the floral fragrance of Bulbophyllum cheiri (fruit fly orchid) is methyl eugenol (ME). In the lowland rain forest of Malaysia, the solitary and nonresupinate flowers of the fruit fly orchid attract only males of the ME-sensitive fruit fly species (Bactrocera carambolae, B. papayae, and B. umbrosa. During the morning, the fruit fly orchid flower is visited by many fruit flies, which can sometimes cover the whole flower. The number of visitors dwindles in the afternoon. Headspace analysis of the flower shows a high ME peak in the morning, a small one between 12:00 and 14:00 hr, and no detectable ME peak after 14:00 hr. The process of pollination in the wild is initiated by attraction of fruit flies to floral ME. The flower, with the aid of its specialized hinged see-saw lip (labellum), temporarily traps (<1 min) a fruit fly pollinator between its lip and column. Just prior to this, the fly is rewarded by the opportunity to feed on the floral attractant found on surfaces of petals, sepals, and lip. The pollinaria borne by two wild B. papayae males (caught on and near the fruit fly orchid flower) are identical in morphology and structure with those obtained from the flower. Many of the B. papayae males (17 of 22 analyzed) attracted to the fruit fly orchid already possessed both ME metabolites, trans-coniferyl alcohol and 2-allyl-4,5-dimethoxyphenol, in their rectal glands, indicating that they had previously consumed ME. In this orchid–fruit fly association, both organisms gain direct reproductive benefits: the orchid flower gets pollinated without having to offer nectar, while the fruit fly boosts its pheromone and defense system, as well as its sexual competitiveness by feeding on the ME produced by the flower.     

Male Sex Pheromonal Components Derived from Methyl Eugenol in the Hemolymph of the Fruit Fly Bactrocera papayae

Pharmacophagy of methyl eugenol (ME)--a highly potent male attractant, by Bactrocera papayae results in the hydroxylation of ME to sex pheromonal components, 2-ally-4,5-dimethoxyphenol (DMP) and (E)-coniferyl alcohol (CF). These compounds, which are also male attractants, are then sequestered and stored in the rectal gland prior to their release during courtship at dusk. Chemical analyses of the digestive tract (excluding the crop and rectal gland) showed the absence of the sex pheromonal components and their precursor, ME. However, B. papayae males were attracted to and fed on the ME-fed male hemolymph extracts but not on hemolymph extracts of ME-deprived males. After thin layer chromatography in a hexane:ethyl acetate solvent system, flies were attracted to and fed on the original point on the TLC plate where the hemolymph extract had been spotted, suggesting that the pheromone components were bound in polar complexes. Chemical analyses of the ME-fed male hemolymph and crop extracts revealed the presence of the sex pheromonal components. The presence of the ME-derived pheromonal components and the absence of ME in the hemolymph suggest that the hemolymph is involved in the transportation of sex pheromonal components from the crop to the rectal gland.     

Mutual Reproductive Benefits Between a Wild Orchid, Bulbophyllum patens, and Bactrocera Fruit Flies via a Floral Synomone

The solitary flower of Bulbophyllum patens selectively attracts male fruit flies of several Bactrocera species with a specific fragrance in the rain forest of Malaysia. It temporarily traps flies between its hinged see-saw lip and column for pollination. The attractant component is zingerone [4-(4-hydroxy-3-methoxyphenyl)-2-butanone], a pungent essence of ginger. Zingerone has a structure resembling two major fruit fly attractants (methyl eugenol and raspberry ketone) and shows potency to attract a wide range of fruit fly species (B. carambolae, B. caudata, B. cucurbitae, B. tau, and B. umbrosa). A fruit fly visitor is rewarded by feeding on zingerone, and in return it removes the pollinarium and then transfers it to another flower. Males of the melon fly acquire the floral essence and selectively store it in the pheromone gland to attract conspecific females. Males of B. papayae, however, convert zingerone to zingerol in the crop. The latter compound is 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.     

Attraction of Female and Male Bactrocera papayae to Conspecific Males Fed with Methyl Eugenol and Attraction of Females to Male Sex Pheromone Components

The attraction of female and male Bactrocera papayae to conspecific males fed with methyl eugenol (ME) and female attraction to male synthetic sex pheromone, trans-coniferyl alcohol (CF), were evaluated in a wind tunnel. Earlier and greater attraction were exhibited by both females and males to ME-fed than to non-ME-fed males as dusk approaches. Males increased their precopulatory behavior (i.e., wing fanning and mounting) during the period of higher attractancy. These data confirm that the consumption of ME enhances the mating competitiveness of males and suggest that ME also functions as a precursor to the male sex and aggregation pheromones. Three phenylpropanoid compounds biosynthesized from ME, coniferyl alcohol, 2-allyl-4,5-dimethoxyphenol, and 3,4-dimethoxycinnamyl alcohol, were detected in male rectal gland along with an endogenous rectal compound, N-(3-methylbutyl) acetamide. When offered singly to the females, coniferyl alcohol was found to be most attractive.     

Synomone Or Kairomone? – <Emphasis Type="Italic">Bulbophyllum Apertum</Emphasis> Flower Releases Raspberry Ketone To Attract <Emphasis Type="Italic">Bactrocera</Emphasis> Fruit Flies

Bulbophyllum apertum flower (Orchidaceae) releases raspberry ketone (RK) in its fragrance, which attracts males of several fruit fly species belonging to the genus Bactrocera. Besides RK as a major component, the flower contains smaller amounts of 4-(4-hydroxylphenyl)-2-butanol, plus two minor volatile components, veratryl alcohol and vanillyl alcohol. Within the flower, the lip (labellum) had the highest concentration of RK with much smaller quantities present in petals; other flower parts had no detectable RK. Male fruit flies attracted to the flower belong to RK-sensitive species – such as Bactrocera albistragata, B. caudatus, B. cucurbitae (melon fly), and B. tau. Removal and attachment of the pollinarium to a flys thoracic dorsum occurred when a male of B. albistragata was toppled into the floral column cavity, due to an imbalance caused by it shifting its body weight while feeding on the see-saw lip, and then freeing itself after being momentarily trapped between the lip and column. During this process, the stiff hamulus (the pollinia stalk protruding prominently towards the lip) acted as a crowbar when it was brushed downwards by the toppled fly and lifted the pollinia out of the anther. If the fly was big or long for the small triangular lip, it would not be toppled into the column cavity and would just walk across the column, during which time the pollinarium could be accidentally removed by the flys leg, resulting in a failed transport of the pollinarium. This suggests an unstable situation, where the orchid relies only on a particular pollinator species in the complex ecosystem where many RK-sensitive species inhabit.Wild males of B. caudatus (most common visitors) captured on Bulbophyllum apertum flowers were found to sequester RK in their bodies as a potential pheromonal and allomonal ingredient. Thus, RK can act either as a floral synomone (pollinarium transported) or kairomone (accidental removal of pollinarium leading to total pollen wastage), depending on the body size of the male fruit flies visiting the flowers.     

Allomonal and hepatotoxic effects following methyl eugenol consumption in Bactrocera papayae male against Gekko monarchus

Methyl eugenol (ME), is converted into two major phenylpropanoids, 2-allyl-4,5-dimethoxyphenol and trans-coniferyl alcohol, following consumption by the male fruit fly Bactrocera papayae. Chemical analysis of wild male B. papayae rectal glands, where the compounds are sequestered, revealed the presence of ME metabolites in varying quantities. These phenylpropanoids are shown to be involved in the fruit fly defense both in no-choice and choice feeding tests against the Malayan spiny gecko, Gekko monarchus. After being acclimatized to feeding on fruit flies, geckos consumed significantly fewer ME-fed male flies than controls that consumed all the ME-deprived male flies offered throughout a two-week period. Diagnosis of dissected livers from geckos that consumed ME-fed male flies revealed various abnormalities. These included discoloration and hardening of liver tissue, whitening of the gallbladder, or presence of tumorlike growths in all geckos that consumed ME-fed male flies. Control geckos fed on ME-deprived male flies had healthy livers. When given an alternative prey, geckos preferred to eat untreated house flies, Musca domestica to avoid preying on ME-fed fruit flie     

Ring-Fluorinated Analog of Methyl Eugenol: Attractiveness to and Metabolism in the Oriental Fruit Fly, <Emphasis Type="Italic">Bactrocera Dorsalis</Emphasis> (Hendel)

Oriental fruit fly, Bactrocera dorsalis (Hendel), males are highly attracted to the natural phenylpropanoid methyl eugenol (ME). They compulsively feed on ME and metabolize it to ring and side-chain hydroxylated compounds that have both pheromonal and allomonal functions. Side-chain metabolic activation of ME leading to (E)-coniferyl alcohol has long been recognized as a primary reason for hepatocarcinogenicity of this compound in rodents. Earlier, we demonstrated that introduction of a fluorine atom at the terminal carbon of the ME side chain significantly depressed metabolism and specifically reduced formation of coniferyl alcohol but had little effect on field attractiveness to B. dorsalis. In the current paper, we demonstrate that fluorination of ME at the 4 position of the aromatic ring blocks metabolic ring-hydroxylation but overall enhances side-chain metabolism by increasing production of fluorinated (E)-coniferyl alcohol. In laboratory experiments, oriental fruit fly males were attracted to and readily consumed 1,2-dimethoxy-4-fluoro-5-(2-propenyl)benzene (I) at rates similar to ME but metabolized it faster. Flies that consumed the fluorine analog were as healthy post feeding as ones fed on methyl eugenol. In field trials, the fluorine analog I was ∼50% less attractive to male B. dorsalis than ME.

Accumulation of Phenylpropanoid and Sesquiterpenoid Volatiles in Male Rectal Pheromonal Glands of the Guava Fruit Fly, <Emphasis Type="Italic">Bactrocera correcta</Emphasis>

The guava fruit fly, Bactrocera correcta, is widely distributed in Thailand and other surrounding Southeast Asian countries, and, like the closely related sympatric species, the oriental fruit fly, B. dorsalis, infests various fruits, including guava, peach, and mango. Males of both B. correcta and B. dorsalis are strongly attracted to, and compulsively feed on, methyl eugenol (ME). Bactrocera dorsalis males fed on ME sequester its metabolite phenylpropanoids, (E)-coniferyl alcohol and 2-allyl-4,5-dimethoxyphenol, in the rectal pheromone gland. In contrast, B. correcta males fed on ME sequester two different metabolites, (Z)-coniferyl alcohol (ZCF) and (Z)-3,4-dimethoxycinnamyl alcohol (DMC), in the rectal gland. Examination of the temporal changes of ME metabolites in B. correcta male rectal glands revealed that the total of ZCF and DMC was as high as 100 μg/male at 24 hr after ME feeding. ZCF and DMC were detected in a large proportion of wild B. correcta males captured at various sites in Thailand. Since B. correcta and B. dorsalis are sympatric species in Thailand, these two different subsets of rectal phenylpropanoids could play a role to avoid interbreeding between the species. Further survey of wild flies in Thailand revealed that a large proportion of males of B. correcta store large quantities (over 250 μg/gland) of sesquiterpene hydrocarbons, including β-caryophyllene, α-humulene, and alloaromadendrene in the rectal gland in addition to, or instead of, ZCF and DMC. Laboratory-reared males also sequestered β-caryophyllene and α-humulene, along with ZCF and DMC, when the sesquiterpenes were artificially supplied together with ME. A field test demonstrated that a mixture (1:1) of β-caryophyllene and α-humulene attracted male B. correcta, albeit in smaller numbers than in traps baited with ME. The sequestration of sesquiterpenes, in addition to the different ME metabolites in the pheromone gland in B. correcta males, contrasts with the situation in B. dorsalis males, suggesting a potential role in intra and/or inter-specific interactions between these sympatric species.     

Sequestration of distasteful compounds by some pharmacophagous insects

Several pharmacophagous insects have been shown to sequester specific kairomonal substances or their derivatives in their body tissues. Turnip sawflies,Athalia rosae, visit a plant,Clerodendron trichototmum (Verbenaceae), and feed voraciously on the leaf surface. Clerodendrins were characterized as the potent phagostimulants forA. rosae adults. The insect sequesters some of the analogs and becomes extremely bitter on its body surface. Some chrysomelid leaf beetles associated with cucurbitacins were found to store high concentrations of these bitter principles in their body. South American polyphagous beetles,Diabrotica speciosa andCerotoma arcuata, are strongly arrested by root components from the cucurbit plant,Ceratosanthes hilariana, and selectively accumulate 23,24-dihydrocucurbitacin D, effectively gaining bitterness. Similarly, four species of Asian pumpkin leaf beetles belonging to the genusAulacophora were shown to sequester the same compound in body tissue as the major bitter principle. Three phenylpropanoids closely related to methyl eugenol were found to accumulate in the rectal glands of the male Oriental fruit fly,Dacus dorsalis. One of the rectal gland components, 2-allyl-4,5-dimethoxyphenol was shown to be released in the air during courtship. In all of these cases, selectively sequestered compounds strongly deterred feeding by some predators, thus serving as allomones in this context. Kairomonal and pheromonal functions linked with allomonal sequestration by pharmacophagous feeding has also been suggested.     

Consumption and Metabolism of 1,2-Dimethoxy-4-(3-Fluoro-2-Propenyl)Benzene, a Fluorine Analog of Methyl Eugenol, in the Oriental Fruit Fly Bactrocera dorsalis (Hendel)

Methyl eugenol (ME) is a natural phenylpropanoid highly attractive to oriental fruit fly Bactrocera dorsalis (Hendel) males. The flies eagerly feed on ME and produce hydroxylated metabolites with both pheromonal and allomonal functions. Side-chain metabolic activation of ME has long been recognized as a primary reason for hepatocarcinogenicity of this compound on rodents. In an attempt to develop a safer alternative to ME for fruit fly management, we developed a fluorine analog 1,2-dimethoxy-4-(3-fluoro-2-propenyl)benzene (I), which, in earlier field tests, was as active to the oriental fruit fly as ME. Now we report that B. dorsalis males are not only attracted to, but also eagerly consume (up to ∼1 mg/insect) compound I, thus recognizing this fluorinated benzene as a close kin of the natural ME. The flies metabolized the fluorine analog I in a similar fashion producing mostly two hydroxylated products, 2-(3-fluoro-2-propenyl)-4,5-dimethoxyphenol (II) and (E)-coniferyl alcohol (III), which they stored in rectal glands. However, the introduction of the fluorine atom at the terminal carbon atom of the double bond favors the ring hydroxylation over a side-chain metabolic oxidation pathway, by which coniferyl alcohol is produced. It also appears that fluorination overall impedes the metabolism: at high feed rate (10 μl per 10 males), the flies consumed in total more fluorine analog I than ME but were unable to metabolize it as efficiently as ME.     

Quantitative analysis of pheromone production in irradiated Caribbean fruit fly males,Anastrepha suspensa (Loew)

Pheromonal volatiles emitted by irradiated and control 5- to 11-day-old Caribbean fruit flies,Anastrepha suspensa (Loew), were collected on Tenax adsorbent filters and quantified by gas chromatography (GC). The components released were identified by comparison of retention times on GC and by mass spectrometry (MS) with authentic synthetic standards. Pharate adults were irradiated with gamma rays from a⁶⁰Co source at a dose rate of 10.3 Gray (Gy)/min. The total dosages given were 30, 50, 70, and 100 Gy. Pheromone volatiles were collected from adult males when they were between 5 and 11 days of age. The compounds quantified were (Z)-3-nonenol and (Z, Z)-3,6-nonadienol, which eluted from the GC column together and were quantified as one peak,-bisabolene, suspensolide, anastrephin, and epianastrephin. Irradiation with 30 Gy did not significantly reduce any pheromonal components, nor did it change the pheromonal blend. In contrast, suspensolide and bisabolene were significantly reduced in flies irradiated with 50 Gy, while the nonenols and epianastrephin were reduced at the 70-Gy dose. Irradiation with the 100-Gy dose reduced all components with the exception of suspensolide.University of Florida Agric. Exper. Sta. Journal Series No.R-03156.     

Inheritance Of Resistance to Mammalian Herbivores and of Plant Defensive Chemistry in an <Emphasis Type="Italic">Eucalyptus</Emphasis> Species

Hybridization in plants provides an opportunity to investigate the patterns of inheritance of hybrid resistance to herbivores, and of the plant mechanisms conferring this resistance such as plant secondary metabolites. We investigated how inter-race differences in resistance of Eucalyptus globulus to a generalist mammalian herbivore, Trichosurus vulpecula, are inherited in their F₁ hybrids. We assessed browsing damage of 3-year-old trees in a common environment field trial on four hybrid types of known progeny. The progeny were artificial intra-race crosses and reciprocal inter-race F₁ hybrids of two geographically distinct populations (races) of E. globulus north-eastern Tasmania and south-eastern Tasmania. Populations of trees from north-eastern Tasmania are relatively susceptible to browsing by T. vulpecula, while populations from south-eastern Tasmania are more resistant. We assessed the preferences of these trees in a series of paired feeding trials with captive animals to test the field trial results and also investigated the patterns of inheritance of plant secondary metabolites. Our results demonstrated that the phenotypic expression of resistance of the inter-race F₁ hybrids supported the additive pattern of inheritance, as these hybrids were intermediate in resistance compared to the pure parental hybrids. The expression of plant secondary metabolites in the F₁ hybrids varied among major groups of individual compounds. The most common pattern supported was dominance towards one of the parental types. Together, condensed tannins and essential oils appeared to explain the observed patterns of resistance among the four hybrid types. While both chemical groups were inherited in a dominant manner in the inter-race F₁ hybrids, the direction of dominance was opposite. Their combined concentration, however, was inherited in an additive manner, consistent with the phenotypic differences in browsing.     

Comparison of Oligosaccharide Compositions in Male Nuptial Secretions of Three Cockroach Species of the Genus Blattella

Male cockroaches of the genus Blattella secrete courtshippheromones from abdominal tergal glands. Conspecific females mount courting males and feed on their tergal exudates. In the German cockroach, B. germanica, a complex mixture of oligosaccharides was previously identified as the major phagostimulants in the male tergal secretion. We compared the oligosaccharide compositions of three Blattella species from different habitats, B. germanica (house), B. lituricollis (field), and B. nipponica (forest), by gas chromatographic (GC) analysis of their trifluoroacetylated derivatives. The three possessed a series of maltooligosaccharides and oligoglucosyl trehaloses with 14 and 11 linkages in common. However, B. germanica was conspicuous for its accumulation of a oligoglucosyl trehalose with a 16 linkage [O--D-glucopyranosyl-(16)--D-glucopyranosyl -D-glucopyranoside] as the most prominent component of the secretion. Such diversification of the male pheromonal compositions within the genus might be reflected by biosynthetic systems in males and chemosensory properties in females suited for their natural habitat.     

Chemistry of fruit flies: Glandular secretion ofBactrocera (Polistomimetes) visenda (Hardy)

The major component (>90% of volatiles) of the male rectal glandular extract of the nonpest speciesBactrocera visenda (Hardy) is 3-methyl2-butenyl acetate, with minor components being the isomeric 3-methyl-3-butenyl acetate, the homologous esters, 3-methyl-2-butenyl propanoate and 3-methyl-2-butenyl formate, along with 3-methyl-2-buten-1-ol, 3-methyl-2-butenal, and 3-methylbutyl acetate. None of these compounds has been identified previously from aBactrocera species, supporting the view thatBactrocera visenda is taxonomically distant from otherBactrocera species identified from the Australian mainland. This collection of compounds adds to the known types utilized by dipteran species and emphasizes their extensive biosynthetic capability.     

Production of pheromone by hairpencil glands of males obtained from interspecific hybridization betweenHeliothis virescens andH. subflexa (Lepidoptera: Noctuidae)

Pheromone produced by the hairpencil glands of interspecific hybrid- and backcross-generation males from crosses betweenHeliothis virescens (F.) withH. subflexa (Gn.) was studied. Males of reciprocal F₁ hybrids, all of which had hairpencil glands morphologically similar to those ofH. virescens, produced neither the same pheromone blend nor amounts of pheromone that were produced by males ofH. virescens. Instead, these hybrid males produced pheromone that was quantitatively and qualitatively similar to that produced byH. subflexa. Hairpencil gland extracts from males obtained from backcrossing F₁ females of either cross to males ofH. subflexa were the same as those ofH. subflexa. However, extracts from backcross males of crosses between F₁ females andH. virescens were variable. Some extracts from these backcross males were like those ofH. virescens while others were either likeH. subflexa or were intermediate between those of the parent species. These results showed that the production of pheromone by the hairpencil glands of hybrid and backcross males is under the dominant regulation of autosomal genes of theH. subflexa genome.     

Effect of Volatile Constituents from <Emphasis Type="Italic">Securidaca</Emphasis><Emphasis Type="Italic">Longepedunculata</Emphasis> on Insect pests Of Stored Grain

Securidaca longepedunculata Fers (Polygalaceae) is commonly used as a traditional medicine in many parts of Africa as well as against a number of invertebrate pests, including insects infesting stored grain. The present study showed that S. longepedunculata root powder, its methanol extract, and the main volatile component, methyl salicylate, exhibit repellent and toxic properties to Sitophilus zeamais adults. Adult S. zeamais that were given a choice between untreated maize and maize treated with root powder, extract, or synthetic methyl salicylate in a four-way choice olfactometer significantly preferred the control maize. Methyl salicylate vapor also had a dose-dependant fumigant effect against S. zeamais, Rhyzopertha dominica, and Prostephanus truncates, with a LD₁₀₀ achieved with a 60 l dose in a 1-l container against all three insect species after 24 hr of exposure. Probit analyses estimated LD₅₀ values between 34 and 36 l (95% CI) for all insect species. Furthermore, prolonged exposure for 6 days showed that lower amounts (30 l) of methyl salicylate vapor were able to induce 100% adult mortality of the three insect species. The implications are discussed in the context of improving stored product pest control by small-scale subsistence farmers in Africa.     

Sabulodes caberata guenée (Lepidoptera: Geometridae)

A 6,9-nonadecadiene, (Z)-9-nonadecene, andn-nonadecane were identified in extracts of sex pheromone glands of femaleSabulodes caberata Guenée. Potential pheromonal activity of gland components was assessed by electroantennogram measurements of gas-chromatographic fractions of abdominal tip extracts. Chemical identification was based on gas chromatography and mass spectrometry of parent compounds, hydrogenation products, ozonolysis products, dimethyl disulfide adducts, and synthesis. The monoene was synthesized via coupling of alkyl and acetylenic intermediates. (Z,Z)-6,9-Nonadecadiene (Z6,Z9-19H) was synthesized from methyl linoleate via chain lengthening. SyntheticZ6,Z9-19H had the same retention times on polar and nonpolar capillary gas-chromatographic columns as the 6,9-nonadecadiene from the sex pheromone glands. In field testsZ6,Z9-19:H alone produced trap catch of maleS. caberata and addition of (Z)-9-nonadecene orn-nonadecane had no effect on trap catch.This paper reports the results of research only. Mention of a commercial product in this paper does not constitute a recommendation by the U.S. Department of Agriculture.     

Identity and Function of Scent Marks Deposited by Foraging Bumblebees

Foraging bumblebees can detect scents left on flowers by previous bumblebee visitors and hence avoid flowers that have been depleted of nectar. Tarsal secretions are probably responsible for this repellent effect. The chemical components of the tarsal glands were analyzed by combined gas chromatography–mass spectrometry for three species of bumblebee, Bombus terrestris, B. lapidarius, and B. pascuorum. The hydrocarbons identified were similar for each species, although there were interspecific differences in the relative amounts of each compound present. The tarsal extracts of all three species comprised complex mixtures of long-chain alkanes and alkenes with between 21 and 29 carbon atoms. When B. terrestris tarsal extracts were applied to flowers and offered to foraging bumblebees of the three species, each exhibited a similar response; concentrated solutions produced a repellent effect, which decreased as the concentration declined. We bioassayed synthetic tricosane (one of the compounds found in the tarsal extracts) at a range of doses to determine whether it gave a similar response. Doses 10^–12 ng/flower resulted in rejection by foraging B. lapidarius. Only when 10^–14 ng was applied did the repellent effect fade. We bioassayed four other synthetic compounds found in tarsal extracts and a mixture of all five compounds to determine which were important in inducing a repellent effect in B. lapidarius workers. All induced repellency but the strength of the response varied; heneicosane was most repellent while tricosene was least repellent. These findings are discussed in relation to previous studies that found that tarsal scent marks were attractive rather than repellent.     

Mating and oviposition byCotesia (=Apanteles) marginiventris (Hymenoptera: Braconidae) in presence of synthetic pheromone ofSpodoptera frugiperda (Lepidoptera: Noctuidae)

Two blends of fall armyworm,Spodoptera frugiperda (J.E. Smith), pheromonal components were evaluated in the laboratory for possible close-range effects on mating and oviposition byCotesia marginiventris (Cresson). Neither a two- nor a five-component blend had any significant effect on mating or parasitization ofS. frugiperda larvae by this parasitoid. Dosages of 200, 400, and 800 g were tested.