Adult black-bordered lemon moths, as the common name suggests, are yellow, and their wings have a black edge. There are no other lines present. There usually are two dark dots on each forewing. The forewings are often bright yellow with a lustrous or glossy look. The hindwings tend to be more muted.
Caterpillars are rather thin, with few hairs. Overall color is grass green, with some lengthwise pale stripes running down the body. Usually see on the leaves of grasses, on which they are perfectly camouflaged.
Similar species: Four other members of genus Marimatha occur in North America, and they look quite similar. However, those other four all have an extra line of some sort on the wings, in the postmedian area (running between the midline of the wing and the outer edge).