I believe this guy is actually Amblycorypha - compare here (earlier instar, but the best pic I could find on the site for markings - I actually just raised one of these guys, must get my pictures up . . ), vs. here for Microcentrum rhombifolium. Though they are both speckled, in Amblycorypha the spots are much more pronounced along the edges of the segments of the abdomen and the pronotum, which matches the nymph pictured above. Also, in Microcentrum rhombifolium (but not Microcentrum retinerve) there's a far more ridged look to the dorsal abdomen - as well as the "tooth" on the anterior edge of the pronotum. The little guy pictured here has neither.

(As an aside - I've noticed in raising katydid nymphs that leg proportion is going to be unreliable until they are mature - leg-to-body proportion changes depending on on the length of time since last molt. Recently molted = short, chubby body, making the legs proportionally longer. Some length of time since molt, ready to molt again = longer body, thus making the legs look comparatively shorter.)

Moved from Angle-wing Katydids.

Moved from Katydids.

Probably a nymph of Microcentrum, judging by the proportion of the hind legs.