Allen good focus on the eyes, what I presume to be mouth parts are not so sharp. I wonder if you could have got the shot without the TC then I reckon you would have had more DOF. Nevertheless an very intersting shot. I remember seeing a programme about these critters, as you indicated they have a remarkably long life cycle and when they emerge they are almost plague like in certain areas.
I like the contrast of the reds and browns against the green surface it is walking upon. Nicely focused and sharp on the eyes but i do wish to see a bit more DOF to get the mouth "grill" a bit more defined.
Light is nicely diffused around the eye area as well.
This is a species we never see this far north - looks like you are making good use of your once-in-13-years opportunity to photograph them. A very colorful insect and good sharpness around the eyes. I would agree with the others that the image would have more impact if the entire "face" area was within your DOF. I think Jon's suggestion of removing the TC might have done the trick.
Nice, I remember being in Nashville one year when these came out and being afraid to open my mouth too far in fear that one would fly in they were so numerous! I agree with others that I would like to see a little more DOF.