## 2 Results and Discussion  
To identify semiochemicals in _O. insecifera_, and sex pheromone candidates in _Argogorytes fargeii_ pollinators, solvent extractions of flowers and insects, and floral headspace sampling, were conducted. Samples of _O. insecifera_ labella were extracted in solvents of increasing polarity, from _n_-hexane, to dichloromethane, to methanol. Headspace volatile sampling was performed using solid phase extraction (SPME). Furthermore, whole females of _A. fargeii_ were extracted in dichloromethane. Due to the very limited number of pollinators available, we were restricted to evaluating biological activity using gas chromatography coupled with electroantennography (GC-EAD). Since we were unable to locate males of _A. fargeii_, GC-EAD was used to detect which components of the various extracts were detected by _A. mystacaus_, a closely related species that is the second main pollinator of _O. insecifera_[9]. Two compounds from the floral extracts were repeatedly EAD-active (elicited responses in six out of 10, and two out of 10 EAD experiments). These two compounds were tentatively identified by mass spectrometry (GC-MS) as a C17 alkene and _n_-pentadecane. In previous studies on _O. insecifera_, _n_-pentadecane (**2**, Figure 1a) was indeed found to be active in EAG experiments, while no alkenes were isolated or identified [11]. Here, we found that _n_-pentadecane and the C17 alkene were present in the female _A. fargeii_ (six extracts of individual insects) and were also present in only minor amounts in floral solvent extracts (three extracts of 10 flowers). We investigated the double bond location by dimethyldisulfide (DMDS) microderivatisation of a semi-preparative GC purified compound that was extracted from the wasp. The observation of identical retention times and mass spectra between the semiochemical isolated from the wasp and the synthesized (_Z_)-8-heptadecene (**1**), before and after treatment with DMDS, meant that the double bond position and configuration of the natural product could be confirmed. Furthermore, a floral extract was treated analogously, and was confirmed to contain identical mass fragments at the same relative intensity and retention time, confirming that the compound detected by _A. mystacaus_ was shared between _O. insecifera_ and female _A. fargeii_. In addition to the semiochemicals identified from flowers, another two C15-alkenes and one C17-diene were identified from females of _A. fargeii_. These compounds were also isolated by semi-preparative GC and treated with DMDS. Candidate compounds were synthesized and co-injected with natural extracts (on two GC columns) and tested with GC-EAD. The monoenes were subsequently confirmed as (_Z_)-6-pentadecene (**3**) and (_Z_)-7-pentadecene (**4**), while the diene was identified as (_Z_,_Z_)-6,9-heptadecadiene (**5**) (Figure 1). The GC-EAD and GC-MS analyses of the floral extracts showed that _n_-pentadecene (**2**) was of low abundance and was electrophysiologically active in only two experiments, while (Z)-8-heptadecene (**1**) was active in six experiments. When tested as synthetics at higher concentrations (100 ng to 1 \(\upmu\)g), both compounds were strongly EAD-active in replicated experiments. However, the additional alkenes **3-5** from _A. fargeii_, when tested as synthetic samples at the higher concentration, elicited consistently less frequent and/or weaker EAD responses compared to the orchid-produced **1** and **2** (Figure 1, Table 1). By analysing the GC-MS traces of floral extracts, it was observed that larger amounts of compounds **1** and **2** were present in headspace samples of flowers compared with solvent extracts. Although headspace extractions and solvent extractions are not directly comparable, our findings indicate that the flowers likely continuously produce compounds (indicated by increasing quantity with an increase in SPME sampling time), rather than depend on stored compounds (indicated by very low amounts in solvent extracts) in the floral tissue.