On flowers of Asclepia erosa. This male was seen with a number of other Pepsis at these milkweeds, for more images of them...and more info on the ID here, see remarks under post below:

 

The species here seems to be either P. pallidolimbata or P. thisbe. Note that a distinguishing character for these two species involves the "mesopleural tubercle", which is located (when present) midway along the ventro-lateral edge of the sclerite just above and in front of the middle coxa...see the labelled position "mt" in Fig. II here). According to Hurd(1), P. pallidolimbata has "mesopleural tubercles usually prominent, dentate"; whereas P. thisbe has "mesopleural tubercles evident, but very poorly developed". I may be incorrect in my interpretation, but I'm thinking the mesopleural tubercle is the widely open "v"-shape along the bottom edge of the mesopleural plate in front of the midleg in the full-size version of the 2nd image of this series. I'm not sure whether that "v" shape...with its small "nub"...would be regarded as prominent or poorly developed (or somewhere in between). I believe the mesopleural tubercle is also visible, again as a widely opeing "v" shape on the bottom edge of the mesopleuron in the female post below (from a different time & place):