Abstract. We report here the identification of the long-range, male-produced sex pheromone of the Old house borer Hylotrupes bajulus. Chemical analysis of hexane extracts obtained by surface extraction from dissected prothoracic glands and from headspace samples of the two sexes, revealed male-specific compounds: (3R)-3-hydroxy-2-hexanone, 2-hydroxy-3-hexanone, the diastereomeric diols (2R, 3R)-2,3-hexanediol and (2S, 3R)-2,3-hexanediol, 2,3-hexanedione, as well as 1-butanol.In wind tunnel bioassays we tested the influence of these male-specific compounds from the prothoracal glands on the behaviour of unmated and mated females. Specific behavioural sequences of the tested females (activity, running behaviour, searching, cleaning, flying, extension of ovipositor) were recorded. Unmated females were attracted by male beetles, headspace extracts of males, synthetic blends of the major pheromone compounds as well as by the components (3R)-3-hydroxy-2-hexanone, and the diastereomeric diols. Hexane, female beetles and 2,3-hexanedione did not attract unmated females. The reactions of mated females to male beetles and headspace samples did not differ significantly from those of the controls. The results of the bioassays show that the two-stage premating behaviour is initiated by emission of a long-range sex pheromone from the male prothoracal glands, which functions as an activator, attractant, and possibly aphrodisiac for unmated females.Key words. Hylotrupes bajulus; Coleoptera; Cerambycidae; male sex pheromone; (3R)-3-hydroxy-3-hexanone; wind tunnel; female response; premating behaviour.The woodboring larvae of the longhorn beetle Hylotrupes bajulus (L.) (old house borer, House Longhorn beetle) are a common pest of coniferous woods in Central Europe and North America. This beetle has been spread worldwide by import of infested woods ~. It is able to infest and to damage most of the common coniferous timbers used in buildings, irrespective of age or nutritional content of the wood. In order to develop biological control methods it would be useful to know more about the chemical mediators of mating and oviposition behaviour of H. bajulus. Female H. bajulus are known to prefer oviposition sites which are infested by conspecifics 2. Moreover, the extracted monoterpenes from the larval frass stimulate oviposition. There are several reports indicating that sex pheromones might be involved in the mating behaviour of cerambycids: male volatiles may attract females from a distance, and female contact pheromones are thought to stimulate mating behaviour in various species 3-6. As far as we know, the only reported chemical structure for a male sex pheromone is from Xylotrechus species 7,a.* To whom correspondence should be addressed.Previous studies on its biology 9" 10, aggression, stridulation behaviour ~1, and copulatory behaviour 12 in H. bajulus suggest there is no long-range female sex pheromone. In another study the existence of a closerange female sex pheromone which elicits the orientation of males was assumed ~3, howe...

In a wind tunnel bioassay the effect of three concentrations of natural extracts of (1) Scots pine wood, Pinus syl6estris, and (2) larval frass on the behavioural response of unmated females and males of the old house borer, Hylotrupes bajulus, was tested and compared to the behavioural effects of the male-produced sex pheromone (3R)-3-hydroxy-2-hexanone. The influence on the behaviour of both sexes was found to be equally significant for the two higher concentrated hexane extracts of wood and larval frass. Therefore several synthetic monoterpenes present in the extracts and ethanol were tested at the two higher concentrations (1:100, 1:1000 vol/vol). Among the higher concentrated monoterpenoid hydrocarbons [(+)-h-pinene, ( +)-i-pinene, (+ )-limonene], only h-pinene increased the activity, orientation towards scent source and interest towards conspecifics. The tests with higher concentrated ethanol and the oxygenated monoterpenes [( − )-verbenone, (− )-trans-pinocarveol, (+ )-terpinen-4-ol, (+)-h-terpineol, (− )-myrtenol] revealed that verbenone is the most effective stimulant for the females, followed by trans-pinocarveol, terpinen-4-ol and h-terpineol. For males, terpinen-4-ol was the only mediator significantly inducing attraction and orientation towards the scent source combined with an interest in conspecifics apparent by fighting or courtship behaviour. Males did not respond to verbenone which is a main compound of larval frass. Myrtenol and ethanol were ineffective in both sexes. In fact behavioural observations suggest that the beetles were repelled by the high dose of myrtenol. Using the ten-fold lower dose of the synthetic monoterpenes (1:1000 vol/vol), all semiochemicals except myrtenol lost activity. Myrtenol, however, induced behavioural responses, like increased activity and orientation towards scent source, only at the low concentration. Based on the results, primary attraction of unmated old house borer is probably mediated by monoterpenes of coniferous wood, while secondary attraction to infested wood would occur in response to volatiles of larval frass.

Three different types of traps were evaluated for a semiochemical-based trapping method for Hylotrupes bajulus (L.) (Cerambycidae). One, designated the ground trap, was the most efficient under both laboratory and natural conditions and had an active space of about 3.5 m. Significantly more beetles were captured in traps baited with a mixture of synthetic pheromones, (3R)-3-hydroxy-2-hexanone [(3R)-ketol] + 1-butanol, than in those with either single compound or with racemic mixtures. Furthermore, the synthetic lure captured more females than two virgin males in a laboratory bioassay. In addition, doubling the concentration of the synthetic pheromone significantly increased trap catches. The present findings have potential value of the management of this pest.

The following compounds were identified as male pheromone components of the longhorn beetles Hylotrupes bajulus and Pyrrhidium sanguineum: (3R)-3-hydroxy-2-hexanone [ (34-11, (2S,3R)-2,3-hexanediol [(2S,3R)-4] and (2R,3R)-2,3-The syntheses of enantiomerically pure samples, enantiomeric separation by chiral gas chromatography and unambiguous structure assignment of the target compounds are described.The old house borer, Hylotrupes bajulus, is an almost cosmopolitan insect of high economic importance. The Iarvae of the beetle may cause serious damage to timber in buildings, and the development of an integrated pest management system to monitor populations would be highly desirable. Within the context of our investigations of systems of chemical communication in beetles, we recently reported on the identification of a male produced pheromone bouquet. The following structures could be assigned; (3R)-3-hydroxy-2-hexanone (1) of more than 99% ee represented the main component, while smaller amounts (5-10%) of almost racemic 2-hydroxy-3-hexanone (2) as well as the corresponding diketone 3 and the diols 4, (2S,3R) 2,3-hexanediol of 34% ee and (2R,3R)-2,3-hexanediol of 31% ee, were also found to be present"]. In this paper we wish to present details of the syntheses and the determination of the absolute configuration of these substances.The synthesis of racemic compounds needed as references for structure confirmation and for the proof of enantiomeric separation in chiral gas chromatography[2] is outlined in Scheme 1. In a Corey-Seebach sequence, n-butanal (5) was coupled to 2-methyl-l,3-dithiane (6) to yield 2-( 1-hydroxybutyl)-2-methyl-l,3-dithiane (7)f31, which was transformed to 3-hydroxy-2-hexanone (l)L4]. A complementary reaction using 2-propyl-1,3-dithiane (8) and acetaldehyde (9) furnished 2-(1 -hydroxyethyl>2-propyl-1,3-dithiane (lo), which was transformed to 2-hydroxy-3-hexanone (2). Reduction of the commercially available 2,3-hexanedione (3) yielded a mixture of the diols 4.

Monoterpenoid compounds extracted from wood of Scots pine, Pinus sylvestris L, synergized the attraction of the old-house borer, Hylotrupes bajulus (L), to the male pheromone (3R)-3-hydroxy-2-hexanone ((3R)-ketol) + 1-butanol. Glasshouse experiments using ground traps baited with extracts derived from Scots pine wood or the monoterpenes (+)-alpha-pinene, (-)-verbenone, (-)-trans-pinocarveol and (+)-terpinen-4-ol attracted significantly more H bajulus females, but caught fewer of them, than the synthetic pheromone mixture alone. Traps baited with higher concentrations of the monoterpene mixture attracted fewer females than those baited with lower dosages, whilst very high concentrations of the mixture (6-10 vials) caught no insects. However, a combination of (3R)-ketol + 1-butanol or (+/-)-3-ketol + 1-butanol with monoterpenes resulted in the capture of significantly more females than either the sex pheromone or the monoterpene mixture alone. Traps baited with a blend of the male's sex pheromone or the monoterpenes attracted significantly more, but caught fewer, males than females. Here again, a combination of the above blends enhanced the attraction of males significantly when compared with the attractancy of either of the compounds/mixtures used alone.