These green tiger beetles were relatively scarce on our afternoon visit to Willcox Playa, we only saw about 5 individuals...compared to many hundreds of C. ocellata. The C. ocellata congregated right near the edges of ponds, whereas the green ones were mostly a bit further from the shore, but still close to the ponds.

In trying to key this in Pearson, Knisley, and Kazilek(1), I got to either C. punctulata or C. nigrocoerula...with the undecidable key break being the presence or absence, respectively, of "microserrations" on the distal edges of the elytra. These microserrations are too small to be discernible in my (or most other) images.

C. punctulata and C. nigrocoerula can be difficult to separate as they look very similar, and their ranges and habitats overlap. Both occur in AZ. Both can be green, blue, or black. Both species have elytral maculations reduced to small dots or absent. And beyond the dense, finely punctate underlying texture of the elytra...both have a line of larger more widely spaced punctures (or "foveae") running parallel and near the inner edges of the elytra, as seen in the posts below:

C. punctulata       vs.     C. nigrocoerula  

Fortunately, the species descriptions in Pearson, Knisley, and Kazilek(1) and Kippenhan (1994) (and detailed figures in the latter) indicate two clear-cut characters that separate the two species:

C. punctulata: First antennal segment with only one seta; labrum entirely white, mildly convex projecting, with a single tooth.
C. nigrocoerula: First antennal segment with two setae; labrum mainly white, with a more-or-less straight, thinly black forward edge, having three teeth.

Pearson et al mention a few other distinctions which, though less clearly-defined, can be helpful:

    1) The rear tips of the elytra come to a point in punctulata vs. being more rounded in nigrocoerula;
    2) The degree of setation of the lateral faces of the thorax is denser in punctulata vs. sparser in nigrocoerula;
    3) The elytra are shinier in punctulata vs. duller in nigrocoerula.

Also, nigrocoerula is typically wider and more robust than punctulata. This character is quantified as follows in couplet 15 of the key in Rumpp (1997):

    4) Elytra narrow & slightly widening up to apical 4th in punctulata vs. elytra evenly arcuate, widest at middle in nigrocoerula.

Unfortunately, none of the clear-cut distinguishing characters (microserrations; 1st antennomere setae; labrum teeth) are discernible in my (or most BugGuide) posts. Nevertheless, in view of all the above, I believe my post here is C. punctulata...e.g. the labrum is convex projecting, the elytra are shiny, etc. Moreover, it looks nearly identical to the image below taken by Alice earlier that afternoon at the same locale:



And the larger version of Alice's image clearly shows a single seta on the 1st antennomere, as well as a convex projecting labrum lacking a black forward edge with 3 teeth. It even looks as if there should almost be enough magnification and resolution to see the microserrations in that image...but I can't make them out (a vertical view would be better for that).