**Identification of (***Z***)-8-Heptadecene and** *n***-Pentadecane as Electrophysiologically Active Compounds in** *Ophrys insectifera* **and Its** *Argogorytes* **Pollinator**

**Björn Bohman 1,2,\*, Alyssa M. Weinstein 3, Raimondas Mozuraitis <sup>4</sup> , Gavin R. Flematti <sup>1</sup> and Anna-Karin Borg-Karlson <sup>5</sup>**


Received: 25 December 2019; Accepted: 14 January 2020; Published: 17 January 2020

**Abstract:** Sexually deceptive orchids typically depend on specific insect species for pollination, which are lured by sex pheromone mimicry. European *Ophrys* orchids often exploit specific species of wasps or bees with carboxylic acid derivatives. Here, we identify the specific semiochemicals present in *O. insectifera*, and in females of one of its pollinator species, *Argogorytes fargeii*. Headspace volatile samples and solvent extracts were analysed by GC-MS and semiochemicals were structurally elucidated by microderivatisation experiments and synthesis. (*Z*)-8-Heptadecene and *n*-pentadecane were confirmed as present in both *O. insectifera* and *A. fargeii* female extracts, with both compounds being found to be electrophysiologically active to pollinators. The identified semiochemicals were compared with previously identified *Ophrys* pollinator attractants, such as (*Z*)-9 and (*Z*)-12-C27-C29 alkenes in *O. sphegodes* and (*Z*)-9-octadecenal, octadecanal, ethyl linoleate and ethyl oleate in *O. speculum*, to provide further insights into the biosynthesis of semiochemicals in this genus. We propose that all these currently identified *Ophrys* semiochemicals can be formed biosynthetically from the same activated carboxylic acid precursors, after a sequence of elongation and decarbonylation reactions in *O. sphegodes* and *O. speculum*, while in *O. insectifera*, possibly by decarbonylation without preceding elongation.

**Keywords:** *Ophrys*; sexual deception; semiochemicals; fly orchid; pollination
