Caladenia crebra spider orchids masquerade as female thynnine wasps to lure male wasp pollinators (pictured). To date, little is known about the chemistry of sexual deception in these orchids. However, some 100 cases of sexual deception presenting in the plant genus.
Björn Bohman, University of Western Australia, Crawley, and Australian National University, Acton, and colleagues, have identified phenolic sulfurous pheromones in the clubs of C. crebra and in female Campylothynnus flavopictus wasp tissues extracted with ethanol or dichloromethane.
Four natural products (pictured; compounds 1–4) were detected by high-resolution GC-MS and compared to synthesized or available reference compounds. Compounds 2, 3, and 4 have not been previously found in nature. Sulfur-containing phenols have only recently been discovered from marine bacteria.
The hydroquinone and formyl aromatic thiols (2 and 3) were identified as potent pheromones. This was done in comprehensive field bioassays in which 923 C. flavopictus male wasp responses were recorded over a two year period.
Conventional electroantennography (insect antennae) techniques did not detect the (methylthio)phenols (4). This leads the team to question whether new and unusual pheromones are underrepresented in pollination research. The study identifies sulfurous pheromones in the insect order Hymenoptera for the first time; it has only once before beeen identified in a sex pheromone for two beetle species.
- The chemical web of a spider orchid – Sulfurous semiochemicals seduce male wasp pollinator,
Björn Bohman, Ryan D. Phillips, Gavin R. Flematti, Russell A. Barrow, Rod Peakall,
Angew. Chem. Int. Ed. 2017.