Similar to M. cinereus, M. bowditchi, & M. pictus, all of which might occur with it. Those species all favor Composite shrubs, but tend to be mostly in semi-arid to arid habitats, often sandy and usually dry in nature. They are usually grayish, brownish, or sometimes have lots of yellowish or blueish coloring. They are only rarely greenish, and then usually have spots on the tegmina and a relatively strong and contrasting pattern of dark brownish to blackish markings. There are minor differences in male genitalia, but females are very simialr structurally.
M. herbaceus is usually associated with riparian areas where there is permanent water, or at least permanent water shallow in the soils, and where mesic plants grow. The usual host plant is the Composite Pluchea sericea (Arrowweed). The insect is usually dull green, with the dark markings even greenish (grayish individuals do occur though). The male furculae are long, broad, truncated, and touch most of their length, and the cerci taper toward the tip, but are still rather wide and truncated at the tip. In related species either the fuculae are long and slender, not touching much; or, the cerci are more slender with the tip narrow and rounded.
Southeastern California and southern Nevada to central New Mexico and western Texas, and south into northern Mexico.
Moist areas (by southwestern standards) near marshes and watercourses mostly in hot desert areas.