We investigated scent composition and pollinator attraction in two closely related orchids, Gymnadenia conopsea (L.) R.Br. s.l. and Gymnadenia odoratissima (L.) Rich. in four populations during the day and night. We collected pollinators of both species using hand nets and sampled floral odour by headspace sorption. We analysed the samples by gas chromatography with mass spectrometry to identify compounds and with electroantennographic detection to identify compounds with physiological activity in pollinators. In order to evaluate the attractiveness of the physiologically active compounds, we carried out trapping experiments in the field with single active odour substances and mixtures thereof. By collecting insects from flowers, we caught eight pollinators of G. conopsea, which were members of four Lepidoptera families, and 37 pollinators of G. odoratissima, from five Lepidopteran families. There was no overlap in pollinator species caught from the two orchids using nets. In the scent analyses, we identified 45 volatiles in G. conopsea of which three (benzyl acetate, eugenol, benzyl benzoate) were physiologically active. In G. odoratissima, 44 volatiles were identified, of which seven were physiologically active (benzaldehyde, phenylacetaldehyde, benzyl acetate, 1-phenyl-2,3-butandione, phenylethyl acetate, eugenol, and one unknown compound). In field bioassays using a mixture of the active G. odoratissima compounds and phenylacetaldehyde alone we caught a total of 25 moths, some of which carried Gymnadenia pollinia. A blend of the active G. conopsea volatiles placed in the G. odoratissima population did not attract any pollinators. The two orchids emitted different odour bouquets during the day and night, but G. odoratissima showed greater temporal differences in odour composition, with phenylacetaldehyde showing a significant increase during the night. The species differed considerably in floral odour emission and this differentiation was stronger in the active than non-active compounds. This differentiation of the two species, especially in the emission of active compounds, appears to have evolved under selection for attraction of different suites of Lepidopteran pollinators.

No abstract

Resulting from several years of field trapping with synthetic compounds at several sites in Hungary, male attractants have been discovered for 2 tineid, 1 heliozelid, 4 gelechiid, 5 coleophorid, 1 plutellid, 4 argyresthiid, 1 oecophorid, 8 tortricid, 3 pterophorid, 2 phycitid and 1 pyralid moth species. This is the first report of a sex attractant for a moth species belonging to Heliozelidae. Among the species captured, Cole0 hora coracipennella, C. hemerobiella, C. trigeminella, Argyresthia albistria, A.agricultural pests, and Emmelina monodactyla is a biological weed control agent. In the case of these species an immediate practical use for the described sex attractants can be expected.sorbiella, Neosp R aleroptera nubilana, and Lobesia bicincta are known as potential or more important IntroductionWhen conducting field tests with the sex pheromone components of a given species, it is not uncommon that males of other species are also attracted to some of the baits. The discovery of sex attractants in this way, although a result of chance rather than design, can be very useful in monitoring the spectrum of occurrence of given chemicals inside taxonomic group(s), and can be helpful in defining practically applicable attractants for agricultural pests.During the past couple of years we have conducted numerous field trapping tests with the aim of defining sex attractant combinations for male noctuids, or optimizing component ratios of known attractants. In the course of these tests males of many microlepidopterous species were also caught. In the present paper we report on the Microlepidoptera for which a sex attractant combination was defined. Materials and methodsField tests were conducted in Hungary by established methods (TOTH et al. 1986;Szocs et al. 1987), using sticky traps similar in shape and size to the ones described in ARN et al. (1979). Moths captured in the tra s were generally removed once or twice weekly, and their species identity was determined by genitaEa analysis.The field test sites were: Adony (Fej6r county): rows of Robinia pseudoacacia L. trees between fields of green peas. Elevation ca 130 m above sea level (a.s.1.).Godollo (Pest county): stands of R. pseudoacacia on a southern slope. Elevation ca 250 m (a.s.1.). Gyongyossolymos (Heves county): pear orchard on the southern slopes of Matra mountains, Budapest (Julianna major): mixed orchard of apple, cherry, plum and pear on a southern hilside, Kompolt (Heves county): alfalfa fields. Elevation ca 130 m ( a d ) . Szabadszillis (Bics-Kiskun county): vineyard on a flat, sandy area. Elevation ca 100 m (a.s.1.). Torokbilint (Pest county): peach orchard on a western hillside. Elevation ca 250 m ( a d . ) . Baits were prepared by applying the appropriate amounts of compounds in hexane solutions to 1 x 1 cm pieces of rubber tubing (Taurus, Budapest, Hungary; No. MSZ Y691/6). When in the test baits containing aldehyde components were used, rubber pieces were boiled 3 times in 70 % ethanol bordered by a mixed oak forest. Elevation ca 300 m (a.s.1.). bo...