Ventral surface showing the distinctive spots on the abdomen--I thought, originally, distinctive for Podisus, following the description in Slater, p. 46, (1). However I had failed to follow the key in depth, and this photo shows the characteristic of a plant-feeding stink bug as shown in Slater, p. 45, fig. 59:
First segment of labium lying in a groove between bucculae so that it is often obscured and the beak often has appearance of not beginning at front of head; bucculae parallel and not coming together posteriorly on underside of head.

Looking at the key for Euschistus in Slater, the line of black spots down the midline appears to key to Euschistus tristigmus Say, described by Slater, p. 56.