Nels and Vincent move back to reproductive isolation – this time, pre-zygotic, in the charismatic orchid bee where the males make chemically distinct perfumes to attract mates of the same species.

Buck and Sean join Vincent in New York, while Sylvia is with Nels in Salt Lake City to discuss the first mutant ant ever made: disruption of orco, a gene required for function of odorant receptors, causes defects in social behavior and fitness.