Protein and amino acid composition of the tergal gland secretions ofBlatta orientalis andEurycotis floridana (Dictyoptera: Blattidae)

Summary Nymphs and adult females ofBlatta orientalis and nymphs ofEurycotis floridana produce a proteinaceous sticky secretion which accumulates on the last abdominal tergites. The proteic patterns do not differ between individuals of the same species. HPLC analyses show that all the common amino acids are found in both species, aspartic and glutamic acids representing 24 to 37% of the total amount of amino acids. InB. orientalis, glutamic acid is the more abundant amino acid whereas inE. floridana it is the aspartic acid. The secretion appears and accumulates rapidly on isolated insects. Behavioural assays revealed that these secretions have a defensive role.     

New repellent semiochemicals for three species of <Emphasis Type="Italic">Dendroctonus</Emphasis> (Coleoptera: Scolytidae)

Summary. Nine compounds identified from captured volatiles of the Douglas-fir beetle, Dendroctonus pseudotsugae, the mountain pine beetle, D. ponderosae, and the spruce beetle, D. rufipennis, that elicited antennal responses in males and females of one or more of these species were tested in the field to determine behavioural activity. 1-Octen-3-ol, found in the volatiles of females of all three species decreased the response of male and female coastal and male interior D. pseudotsugae and both sexes of D. ponderosae to their aggregation pheromones. Acetophenone, identified in the volatiles of females of all three species, significantly decreased the response of interior female D. pseudotsugae. trans-Verbenol, a potent aggregation pheromone of D. ponderosae, decreased the response of both sexes of D. pseudotsugae, while 3-methyl-2-cyclohexen-1- one (MCH), the antiaggregation pheromone of D. pseudotsugae and D. rufipennis decreased the response of both sexes of D. ponderosae. While it has been demonstrated that semiochemical mediated interspecific communication occurs among bark beetles infesting the same host, this study demonstrates that beetles can perceive signals emitted by heterospecifics attacking nonhosts and can potentially use them to avoid attacking the wrong species of conifer.     

Sex pheromones and their potential role in the evolution of reproductive isolation in small ermine moths (Yponomeutidae)

Summary Sex pheromone communication in the nine European species of small ermine moths (Yponomeuta) is reviewed in regard to the potential role of pheromones in the speciation process. Six of the nine species studied (viz.,Y. evonymellus, Y. cagnagellus, Y. padellus, Y. irrorellus, Y. plumbellus, andY. vigintipunctatus) use a mixture of (E)-11-and (Z)-11-tetradecenyl acetate in different ratios as primary pheromone components, with combinations of tetradecyl acetate, (Z)-9-tetradecenyl acetate, (Z)-11-hexadecenyl acetate and the corresponding alcohols of the acetates as additional pheromone components. Analysis of (Z)- to (E)-11-tetradecenyl acetate ratios produced by individual females of these species demonstrated significant variation among females of all species. However, the ranges of ratios produced byY. cagnagellus, Y. irrorellus, andY. plumbellus, sharing the same host-plant species, spindle tree, did not overlap. Niche separation of all six species mentioned required consideration of at least one additional pheromone component or of temporal aspects. The remaining three species,i.e. Y. malinellus, Y. mahalebellus andY. rorellus, have pheromones that differ qualitatively.Biosynthetic routes to the pheromone components identified are proposed on the basis of fatty acid pheromone precursors found in the pheromone glands. A phylogenetic tree for the genus is constructed based on allozyme frequency data and changes in pheromone composition are superimposed on this tree. We suggest that the ancestral ermine moth pheromone is a mixture of (Z)-11- and (E)-11-tetradecenyl acetate and the corresponding alcohols, and a scenario of how present-day patterns evolved is outlined. The pheromone differences among the three species using spindle tree as their host-plant might have evolved throughreproductive character displacement upon secondary contact between populations that had already diverged genetically in allopatry. Pheromone differences within the so-calledpadellus-complex (includingY. cagnagellus, Y. mahalebellus, Y. malinellus, Y. padellus, andY. rorellus) in which species might have originated sympatrically, may have evolved byreinforcing selection as these species still hybridise and produce viable offspring when confined in cages. The role of pheromones in reproductive isolation amongYponomeuta species is emphasised by (1) the function of pheromone components of some of the species as behavioural antagonists to other species, (2) the cross-attraction under experimental conditions between allochronic species with similar pheromones, and (3) the formation of hybrids in the laboratory between species that are isolated in nature by pheromone differences.     

Green leaf volatiles enhance sex attractant pheromone of the tobacco budworm,Heliothis virescens (Lep.: Noctuidae)

Summary Components of the green leaf volatile complex (Z-3-hexenyl acetate andE-2-hexenyl acetate) were shown to enhance responses of tobacco budworm,Heliothis virescens, males to the sex attractant pheromone of conspecific females in the field. The results are discussed with regard to green leaf volatiles which enhance the attractant pheromone of a cohabiting species, and serve as attractants of a parasitoid of conspecific larvae.     

Host-plant green-leaf volatiles synergize the synthetic sex pheromones of the corn earworm and codling moth (Lepidoptera)

Summary The capture of adult male moths in female sex pheromone traps of two key agricultural pests, the corn earworm (Helicoverpa zea) and the codling moth (Cydia pomonella), is enhanced or synergized by a certain group of host-plant volatiles, the green-leaf volatiles (GLVs). Since female adults of both species call and release their sex pheromones while perched upon the leaves of their host-plants, the volatile constituents from the leaves of a number of host-plants were compared. Sex pheromone traps containing one of the prominent leaf volatiles of certainH. zea hosts, (Z)-3-hexenyl acetate, not only significantly increased the capture ofH. zea males but were preferred over traps baited only with sex pheromone. Similarly, traps baited with synthetic sex pheromome ofC. pomonella plus a blend of GLVs captured significantly more males than traps baited only with sex pheromone. Since male moths are not captured in traps baited only with these GLVs, it appears that these GLVs act as pheromone synergists which increase or enhance the attraction or arrestment of male moths in pheromone traps.     

Nutritional phagostimulants function as male courtship pheromone in the German cockroach, <Emphasis Type="Italic">Blattella germanica</Emphasis>

Summary. Males of the German cockroach, Blattella germanica, secrete a pheromonal substance from the abdominal tergal glands, which elicits a feeding response in females during the sequential courtship behavior. The nuptial secretion consists predominantly of a synergistic mixture of sugars and phospholipids. Cholesterol and a series of amino acids, which are also components of the males glandular secretion, significantly enhanced the phagostimulant activity of the sugar components. The nuptial feeding behavior of the female cockroach is therefore elicited by a complex assortment of nutritive components in the male tergal secretion, including sugars, phospholipids, cholesterol, and amino acids. These results indicate that a mixture of primary metabolites, and not of specific secondary metabolites, serves as a pheromonal cue that appeals to the females gustatory sense and effectively brings her to the precopulatory position. Although the male secretion consists of nutrients, we suggest that these compounds probably do not represent a significant nutrient investment in females and their progeny but rather function as a signal in the mating sequence of B. germanica.     

The aggregation pheromone ofIps duplicatus and its role in competitive interactions withI. typographus (Coleoptera: Scolytidae)

Summary Ips duplicatus withI. typographus co-inhabiting Norway spruce (Picea abies (L.) Karst.) would benefit from a pheromone blend distinct from that of the larger competitorI. typographus. GC-MS analysis showed thatI. duplicatus males feeding in the host produced ipsdienol (Id),cis-verbenol (cV),trans-verbenol (tV), myrtenol (Mt), andE-myrcenol (EM) and traces of 2-methyl-3-buten-2-ol (MB).I. duplicatus produced Id in approximately racemic form (48.9-54.5% (+)-(S)-isomer). The amounts of Id and EM released over a 9 day period had a maximum of 250 and 5 ng/h/male, respectively, on day 2. Exposure ofI. duplicatus males to myrcene and -pinene resulted in the production of small amounts of Id, cV, tV, Mt, andtrans-pinocarveol, but not of EM. In laboratory bioassays with walking beetles, the pheromone component Id alone was weakly attractive while EM was inactive, but in binary combination with Id strongly synergized attraction. A combination of EM and Id at a release rate equivalent to 100–200 males was more attractive in the field than 70 unmated males in a spruce log. The addition of myrcene ( a suggested pheromone precursor of Id) to Id did not enhance trap caches, while addition of EM increased catches > 10-fold. Subtracting EM from a blend of Id, EM, cV and MB drastically reduced trap catches while subtraction of cV or MB or both had no significant effect. Addition of EM over a wide concentration range to the synthetic pheromone ofI. typographus did not reduce the attraction of females of this species in the laboratory. A two-species pheromone interaction field test releasingI. typographus pheromone components (MB + cV) at 10–1000 male equivalents (ME) andI. duplicatus pheromone (Id + EM) at 0, 10–1000 ME in all possible combinations showed both positive intraspecific dose-response effects and an interspecific inhibition. Higher release rates of EM appeared to inhibitI. typographus, especially males. In a tree colonization model, the response of the two competing species to their respective pheromones show a good separation during the mass-attack with a small initial cross-attraction. It remains to be shown whether either of the two pheromone systems have in fact evolved in the present sympatry, or if they are an incidental effect of ancestry of these phylogenetically distantIps.     

Comparison of the flower scent of the sexually deceptive orchid <Emphasis Type="Italic">Ophrys iricolor</Emphasis> and the female sex pheromone of its pollinator <Emphasis Type="Italic">Andrena morio</Emphasis>

Summary. Ophrys flowers mimic the female produced sex pheromone of their pollinator species to attract males for pollination. The males try to copulate with the putative female and thereby pollinate the flower. Using electrophysiological and chemical analyses, floral volatiles released by O. iricolor as well as the female sex pheromone of its pollinator species, Andrena morio are investigated. Overall, 38 peaks comprising 41 chemical compounds, were found to release reactions in the antennae of male A. morio bees. Analyses using coupled gas chromatography-mass spectrometry revealed the presence of alkanes and alkenes with 20 to 29 carbon atoms, aldehydes (C9 to C24) and two esters. Almost all of those compounds were found in similar proportions in both, the floral extracts of O. iricolor and cuticle surface extracts of A. morio females. The pattern of biologically active volatiles described here is very similar to that used by other Ophrys species pollinated by Andrena males.     

Indirect evidence indicates female semiochemicals release male precopulatory behaviour in the snow crab,Chionoecetes opilio (Brachyura: Majidae)

Summary Experiments were conducted in aquaria to test the hypothesis that females of the snow crab,Chionoecetes opilio, release a sex pheromone to attract mates. Males exhibited significantly increased activity to water from a source aquarium containing recently-moulted pubescent females, egg-stripped multiparous females and recently-moulted immature females than to water from an aquarium containing berried multiparous females, eggs alone, adolescent males or an empty aquarium. Males without their cephalic chemoreceptors maintained low activity levels in the presence of recently-moulted pubescent females, whereas maxilla-ablated males reacted as strongly as intact males. These findings are discussed within the context of the ecdysteroid-sex pheromone hypothesis, proposed by Kittredgeet al. (1971) and Kittredge & Takahashi (1972), but subsequently rejected. We propose that ecdysteroids from both pubescent and multiparous females may elicit male search-and-clasp behaviour inC. opilio and that the reproductive biology of species used to refute the hypothesis was inappropriate to test the role of ecdysteroids as a cue in the mating process.     

Chemoecological studies of the exocrine glandular larval secretions of two chrysomelid species (Coleoptera):Phaedon cochleariae andChrysomela lapponica

Summary The exocrine glandular secretions of larvae of the subfamily Chrysomelinae are known to repel conspecific adults, other competitive phytophagous insects and natural enemies. InPhaedon cochleariae, the intraspecific activity of tlc fractions of the larval secretion was tested in order to examine the ecological significance of two fractions containing minor components and a fraction containing the major compound, the cyclopentanoid monoterpene (epi)chrysomelidial. InChrysomela lapponica, the defensive activity of the larval secretion against ants is known from specimens feeding upon willow or birch. The feeding preferences of larvae and adults ofC. lapponica from a Finnish and a Czech population were tested. The Finnish individuals significantly preferred feeding uponSalix borealis, whereas they hardly fed upon birch. The Czech specimens clearly preferred birch (Betula pubescens) to willow species. Application of salicin onto leaves of a willow species free of this phenolglycoside revealed that the Finnish individuals preferred feeding upon leaves with salicin. On the other hand, the Czech individuals avoided feeding upon leaves ofB. pubescens treated with salicin. The chemical composition of the glandular secretion of the Finnish larvae differed from the one of the Czech larvae. GC-MS-analyses of the secretions revealed that salicylaldehyde was the only major component of the secretion of Finnish larvae feeding upon the salicin-containing willowS. borealis. The glandular secretion of the Czech larvae feeding upon birch contained numerous esters of isobutyric acid and 2-methylbutyric acid. When Czech larvae had fed upon a salicin-containing willow (S. fragilis), the major compounds of their secretion were benzoic acid, salicylalcohol and benzoic acid esters; salicylaldehyde was only detected in traces. Thus,C. lapponica individuals from the Finland population adapted so closely to a salicincontaining willow that they clearly prefer this plant for food and that they obviously derive their main larval defensive compound (salicylaldehyde) from their host-plant.     

Chemical defense of a rare mint plant

Summary Analyses of leaf extracts ofDicerandra frutescens, a highly aromatic mint plant from central Florida listed as an endangered species, revealed presence of 12 closely related monoterpenes. The principal of these, (+)—trans-pulegol, is a new natural product, the synthesis of which is described. The terpenes are produced in glandular capsules that release their contents upon injury of the leaf. Data from bioassays with ants and cockroaches indicate that the terpenes serve for defense against insects.Dicerandra does, however, have a leaf-eating enemy, the caterpillar of a pyralid moth,Pyrausta panopealis. The discovery of a new natural product from an endangered species raises questions about the chemical implications of species extinction.     

Sexually differentiated functions of female-produced pheromone of the black chafer <Emphasis Type="Italic">Holotrichia loochooana loochooana</Emphasis> (Sawada) (Coleoptera: Scarabaeidae)

Summary. Both male and female Holotrichia loochooana loochooana (Sawada) (Coleoptera: Scarabaeidae) were attracted with female-produced pheromone, anthranilic acid (2-aminobenzoic acid), in the field. Male chafers were observed to apparently directly locate cotton balls impregnated with 1 to 10 mg of pheromone. In contrast, females never directly oriented to the treated balls but landed 0.2-1.5 m away and exposed their abdominal glands in a calling posture, which occasionally resulted in aggregation of both females and males. This suggested the mating aggregation of this species could be primarily induced by pheromone released by females. A hypothesis for adaptability of female aggregation is proposed and discussed.     

Identification of trail pheromone compounds from the labial glands of the stingless bee Geotrigona mombuca

Foragers of several species of stingless bees deposit pheromone spots in the vegetation to guide recruited nestmates to a rich food source. Recent studies have shown that Trigona and Scaptotrigona workers secrete these pheromones from their labial glands. An earlier report stated that species within the genus Geotrigona use citral from their mandibular glands for scent marking. Since convincing experimental proof for this conjecture is lacking, we studied the glandular origin of the trail pheromone of Geotrigona mombuca. In field bioassays, newly recruited bees were diverted by artificial scent trails that branched off from the natural scent trail deposited by their nestmates only when they were baited with extracts from the foragers’ labial glands. Compounds extracted from the mandibular glands, however, did not release trail following behavior. This demonstrates that the trail pheromone of G. mombuca is produced in the labial glands, as in Trigona and Scaptotrigona. Furthermore, in chemical analyses citral was identified exclusively in the foragers’ mandibular glands, which disproves its supposed role as a trail pheromone. The labial glands contained a series of terpene- and wax type esters, with farnesyl butanoate as major constituent. We, therefore, postulate that the trail pheromone of G. mombuca is composed of a blend of esters.     

Sex pheromone communication of tentiform leaf-miners <Emphasis Type="Italic">Phyllonorycter insignitella</Emphasis> and <Emphasis Type="Italic">Ph. nigrescentella</Emphasis> from two related species groups

Summary.  Females of both species start their pheromone-releasing activity on the second day after emergence at the beginning of the photophase. During the present work, a peak of calling activity with close to 100% of active Ph. nigrescentella females was registered 1.5 hour after the light had been put on. The high pheromone release behaviour with 50% active females lasted for 3 hours. The calling activity of the group of females was about 6 h/day. The beginning of a photophase under laboratory conditions or an early morning in nature is a common period for sex pheromone release in the genus Phyllonorycter. (8Z,10E)-tetradecadien-1-yl acetate (8Z,10E-14:Ac), (8Z,10E)-tetradecadien-1-ol (8Z,10E-14:OH) and (8E,10Z)-tetradecadien-1-yl acetate (8E,10Z-14:Ac) in the ratio 96:4:traces as well as 8Z,10E-14:Ac and 8Z,10E-14:OH in the ratio 88:12 collected by Solid Phase Micro Extraction (SPME) were found to be specific for the calling periods of virgin Phyllonorycter insignitella and Ph. nigrescentella females respectively. Field trapping experiments demonstrated that all three compounds are important for the attraction of Ph. insignitella males while only 8Z,10E-14:Ac is the essential sex pheromone component for Ph. nigrescentella. The pheromone activity of all three compounds is reported for the first time. Addition of either 8Z,10E-14:OH or 8E,10Z-14:Ac to 8Z,10E-14:Ac did not have a significant effect on the attraction of Ph. nigrescentella males, while the efficiency of the three component blend was 5 times lower as compared to that of 8Z,10E-14:Ac. Our data demonstrate that 8Z,10E-14:OH and 8E,10Z-14:Ac play a dual function, they are minor sex pheromone components of Ph. insignitella essential for attraction of conspecific males and show an allelochemical, antagonistic effect on Ph. nigrescentella males and, thus, ensuring specificity of the mate location signal in two related Phyllonorycter species.     

Temporal accumulation of phenylpropanoids in male fruit flies, <Emphasis Type="Italic">Bactrocera dorsalis</Emphasis> and <Emphasis Type="Italic">B. carambolae</Emphasis> (Diptera: Tephritidae) following methyl eugenol consumption

Summary. Males of dacine tephritids, Bactrocera carambolae and B. dorsalis are strongly attracted to, and compulsively feed on methyl eugenol (ME), a potent attractant for many Bactrocera species. While ME was shown to be biotransformed into phenylpropanoids, 2-allyl-4,5-dimethoxyphenol and (E)-coniferyl alcohol, and temporarily stored in the rectal gland of male B. dorsalis prior to release during courtship at dusk, B. carambolae male produces only the latter compound along with its de novo synthesized pheromone components. Both species were also shown to have different age-related response, sensitivity and consumption levels of ME. Here, we monitored and compared temporal changes in the accumulation profiles of these phenylpropanoids by the two sibling species, with male rectal glands being individually excised at different time intervals from 15 minutes to 20 days after initial ME feeding and analysed quantitatively. Results are discussed in light of plant-fruit fly co-evolution relationship.     

Cleptoparasitism increases the host finding ability of a polyphagous parasitoid species,<Emphasis Type="Italic"> Rhopalicus tutela</Emphasis> (Hymenoptera: Pteromalidae)

Host finding abilities were investigated in the braconid Coeloides bostrichorum and the pteromalid Rhopalicus tutela, two ectoparasitoid wasps attacking the late instar of the bark beetle Ips typographus. Under laboratory conditions, important differences in the host-searching behaviour of these species were found, R. tutela being highly mobile as compared to C. bostrichorum. In the presence of C. bostrichorum, R. tutela behaved as a cleptoparasitoid, displacing the females from their oviposition sites and stealing the hosts previously located by the braconid. This behaviour facilitated host finding in R. tutela and could partly explain the relative success of the polyphagous R. tutela when occurring with the more specialised C. bostrichorum.Communicated by R.F.A. Moritz     

Aphid alarm pheromone (E)-β-farnesene: A host finding kairomone for the aphid primary parasitoidAphidius uzbekistanicus (Hymenoptera: Aphidiinae)

Summary The present study aimed to test the possible function of the aphid alarm pheromone (E)--farnesene (EBF) as a host finding kairomone for aphid primary parasitoids. Extracts of volatile emissions of undisturbed aphids and of aphids under parasitoid attack were obtained by air entrainment. Extracts of cornicle secretions were gained by disturbing aphids and taking their secretions into solution. Extracts were compared by gas chromatography. Only air entrainments of aphids under attack and solvent extracts of cornicle secretions contained the alarm pheromone. In Y-tube olfactometer bioassays, femaleA. uzbekistanicus were attracted to aphid groups under attack of parasitoids, presumably by released EBF. High concentrations of synthetic EBF (1.4 µg to 5.7 µg) also attractedA. uzbekistanicus females. Females with oviposition experience reacted more readily to lower concentrations of EBF than females without experience. In experiments designed as Petri-dish bioassays, the test animals could contact filter paper discs that were treated with solutions containing EBF. Behavioural effects like antennation or stinging attack were not observed. With computer video analysis of parasitoid movements, some effects onA. uzbekistanicus behaviour were detected, again indicating attraction to EBF.As the volatile aphid alarm pheromone attractedA. uzbekistanicus females, it can be concluded that this chemical stimulus acts as a host finding kairomone for this parasitoid species. However, its effect over long distances seems to be limited due to the relatively high concentrations required for reactions. Of two other parasitoid species examined (P. volucre andL. testaceipes) onlyP. volucre was also significantly attracted to the volatile EBF in the Y-tube olfactometer.     

Female sex pheromone in immature insect males—a case of pre-emergence chemical mimicry?

Sexual selection by competition for mates is a formidable force that has led to extraordinary adaptations in males. Here we present results suggesting a novel case of pheromone mimicry in males of Lariophagus distinguendus, a parasitic wasp of beetle larvae that develop in stored grain. Females of L. distinguendus produce a pheromone even before they emerge from a grain. Males are attracted to the parasitised grain and wait for females to emerge. Males emerging later than others are under enormous selection pressure since females mate only once. We show evidence that developing males fool their earlier emerging competitors by mimicking the female pheromone. Males exposed to pupae of either sex exhibit typical courtship behaviour. Searching males are not only arrested by grains containing developing females but spend as much time on grains containing developing males. Hence, by distracting their competitors away from receptive females late males may increase their own chance to mate with these females. After emergence, males decompose the active compounds within 32 h probably to decrease molestation during their own search for mates. Chemical analyses of active pheromone extracts and bioassays using fractions demonstrate that the active compounds are among the cuticular hydrocarbons.     

Identification and biological activity of sex pheromone components from females of the plum moth Illiberis rotundata Jordan (Lepidoptera: Zygaenidae: Procridinae)

The plum moth, Illiberis rotundata Jordan (Lepidoptera: Zygaenidae: Procridinae), is a pest of orchards in Japan and China. Few chemical ecological studies have been directed towards the Zygaenidae and particularly the Procridinae. To investigate the sex pheromone of this species, extracts of pheromone glands from adult female I. rotundata were analyzed by coupled gas chromatography-electroantennography (GC-EAG) and coupled gas chromatography-mass spectrometry (GC-MS). Whilst GC-EAG on male moths showed an active peak, identified as 2-butyl (7Z)-dodecenoate, GC-MS also revealed the presence of the homologue 2-butyl (9Z)-tetradecenoate. Electroantennographic investigations, as well as field tests, strongly suggested the natural compounds to have the (R)-configuration at the stereogenic centre. Field results demonstrate 0.2 mg of a 1:1-mixture of (2R)-butyl (7Z)-dodecenoate and (2R)-butyl (9Z)-tetradecenoate to be a powerful lure that may be used in pest control measures against I. rotundata. The chemical structures of the new pheromone components show the same features as those of other zygaenid species: unsaturated fatty acids esterified with a short chain chiral alcohol. This is the first example of a two-component blend constituting the pheromone of a procridinid species.     

Attraction of field-flying aphid males to synthetic sex pheromone

Summary Transparent plastic water traps, baited with the synthetic aphid sex pheromone components (4aS,7S,7aR)-nepetalactone and (1R,4aS,7S,7aR)-nepetalactol or control lures, were placed in four semi-sheltered field sites at a height of 1.1 m. Although males of twenty-one aphid species were collected from the water traps, onlySitobion fragariae (Walker) was abundant. In total, 8 pheromone traps produced 102 males compared with only 10 males in 8 control traps. The sex pheromone released by sexual femaleS. fragariae was identified as the nepetalactone used in the lures. Aphid sex pheromones may be more species-specific than previously thought and the presence of a host plant is not essential for males to locate sexual females.