The Light Marathyssa moth has a wingspan of 1 to 1.25 inches. The forewing is pale yellowish-brown. The postmedian line meets the inner margin at an oblique angle. The male has bipectinate antennae. The abdomen has 2 white longitudinal lines and fine, white bands at the segments. The abdomen is curled into a “C” shape when at rest. This moth is very similar to Dark Marathyssa. Dark Marathyssa is generally grayer and darker. The male has filiform antennae. The caterpillar is white with bold black spotting and yellow supraspiracular spots. The head is yellow with 2 black spots. It grows to 1 inch.