Pilostyles thurberi is a dioecious stem parasite on the leguminous shrub Dalea formosa. To date, there have been no studies on the pollination ecology of this enigmatic holoparasite. We observed pollinators and analyzed floral scent chemistry of P. thurberi in two populations in north central Texas. Floral visitors were observed and collected throughout the day for 1-2 days at each site. To discriminate between pollinators and non-pollinating visitors, behavior and constancy of insects was noted, and collected insects were examined for placement of pollen on the body. Scent from seven male and six female flower clusters was collected using dynamic headspace sampling using Super Q adsorbent traps and eluted into hexane in the field. Negative control samples were also collected from uninfected Dalea hosts and from ambient air. Samples were analyzed with GC/MS and peaks tentatively identified using known standards and by comparison to mass spectra databases.
Results/Conclusions

Both male and female flowers were visited by male Augochloropsis bees and several taxa of wasps. These taxa were observed at both sites collecting nectar from flowers of both sexes and appeared to be foraging with constancy on P. thurberi. A prevalent constituent of floral scent in both sexes is raspberry ketone (4-(4-Hydroxyphenyl)-2-butanone), a known insect attractant. This is the first study to provide preliminary data on the reproductive biology of any Pilostyles species.