I really appreciate all of the help sorting out the different instars. I dumped the whole lot of them into the guide for now, but any or all can be frassed as others see fit. I will try to fill in the missing instars this summer. I did have a couple of questions...
1) The adults I have photographed have short wings, much shorted than body length, but the rest of the images in the guide have wings coming close to body length or longer than the body. Is this maybe due to subspecies punctulatus vs. griseus, gender, or just variability?
2) In the guide under "Season" it says Typically July-November in much of range. July-September (Michigan), September-November (North Carolina). July-January (Florida). Is seeing 2nd instars in early June atypical, or is the info possibly inaccurate due to no one noticing early instars up in trees?

Your welcome.
The June date for nymphs is not unusual, in fact it sounds just right to me. It will probably vary some from year to year with the weather. Generally the dates given in most literature are for when the adults are present, unless more detail is specified. Nymphs tend to be ignored for a few reasons - they are small, inconspicuous and they don't have wings, so don't get noticed; they are also often difficult to identify, so tend to be ignored on that count too. As for the short wings on yours, they would still qualify as "long" in most identification keys. Some of your adult pictures are of females that are full of eggs, and that makes the abdomen stretch to a longer length. Sometimes right after they have laid their eggs the abdomen is very distended, and even longer. The wings are usually described as "slightly exceeding the hind femur" for this species, which is true of yours. However, the wings do vary a lot in length from place to place and individual to individual. I think females tend to have slightly shorter wings than males too. I don't know if the name "griseus" deserves subspecies status or not, and to be honest I don't know what makes it distinct (if anything) either. Most of my references are rather old, and they list the name as simply a synonym of M. punctulatus; however, you may have that correct (?).