## 1 Introduction  
Pseudocopulation as a means of pollination was first reported over 100 years ago, in two parallel systems [1, 2]. [PERSON] and [PERSON] made observations of European _Ophrys_ orchids [1], while in Australia, _Cryptostylis_ orchids were reported to use the same sexually deceptive strategy, in which insect pollinators attempt copulatory or courtship behaviour with the flower, thereby transferring pollinia [2, 3]. Insect sexual attraction is induced through chemical and physical mimicry of female insects. Pollination by sexual deception is now known to be a phenomenon that has evolved independently multiple times on different continents. There are several hundred confirmed cases in the Orchidaceae, with many more likely to be discovered with future studies [4, 5, 6]. There are also single reports of sexual deception in the Asteraceae [7] and Iridaceae [8], indicating that this pollination strategy may be more common than is currently known. Following the initial observations of pollination via sexual deception in _Ophrys_ and _Cryptostylis_ orchids, an intensive Swedish research program was launched in 1948 to investigate the chemical cues underlying this bizarre pollination strategy. _Ophrys insecifera_ and some southern European _Ophrys_ and their solitary bee pollinator species were the main study species [9]. In these early studies, field experiments demonstrated that floral volatiles were the key to pollinator attraction [9; 10]. With the use of electroantennography (EAG), it was later shown that two species of male sphecid wasp pollinator, _Argogorytes mystacus_ and _A. [PERSON]_, unlike their conspecific females, responded to tentatively identified alkanes, alkenes, and terpen in sorption headspace extracts of _O. insecifera_ flowers [11]. A few years later, the first evidence of chemical mimicry of several species of _Andrena_ bee pollinators by _O. fusca_ and _O. lutea_, was found: aliphatic alcohols, monoterpene- and sesquiterpene alcohols, and aldehydes attracted the patrolling males to varying degrees [12; 13]. The first identification of pollinator sexual attractants in the genus _Ophrys_ did not occur until the late 1990s, with the successful structural elucidation of attractants from _O. splegodes_[14; 15]. A key to the detection and identification of the semiochemicals from this species was the use of gas chromatography coupled with electroantennogram detection (GC-EAD), which revealed a set of 14 electrophysiologically active compounds to be shared among the orchid and the female of its bee pollinator, _Andrena nrigoarenea_. Before being confirmed as attractants in field bioassays, these compounds were identified by GC-MS, including microderivatisation experiments, as a series of long-chained alkanes and alkenes. Furthermore, three (_Z_)-7 alkenes were discovered to be responsible for the attraction of male _Colletes cunicularius_ bees to _O. exaltata_[16]. The chemical stimuli for the sexual attraction of various _Ophrys_ pollinators also include other types of structures, as shown when a mixture of hydroxy- and keto acids, together with aldehydes and esters, were identified as the attractants in _O. speculum_, which is pollinated by male _Campsoscolia ciliata_ scolid wasps [17]. In Australian sexually deceptive orchids, 1,3-cyclohexanediones (chiolgolottones) have been identified as pollinator attractants in _Chiloglottis_[18], as have hydroxymethylpyrazines and a \(\beta\)-hydroxlactone (drakolide) in _Drakaea_[19; 20; 21; 22], (methylthio)phenols, acetophenones and monoterpenes in _Caladenia_[23; 24; 25], and tetrahydrofuran acid derivatives in _Cryptostylis_[26]. Besides the discovery of a broad range of compounds pivotal for pollination in sexually deceptive orchids, there has also been interest in the biosynthesis of these compounds, with the aim to link biosynthesis to the evolution and speciation of orchids.