Yellow Myzinum of Texas

So, it appears that these wasps are more than one species if we accept that the yellow scapes and black scapes represent 2 groups. So why are they yellow? Well, one possibility is natural selection, say if the flowers in Houston are more yellow, maybe the brighter wasps are better protected from predators and more likely survive than their darker brethren. Another possibility would be if the opposite sex finds the brighter colored wasps more attractive. Or a combination of the 2.