Macronoctua onusta, commonly known as the iris borer, is a species of cutworm or dart moth in the family Noctuidae.

[1][2][3] Macronoctua onusta is a large brown and smoky dark gray moth (FW length 18–21 mm).

It is dull brown with broad smoky dark gray suffusion on the costa and in the cell as well as in the terminal area and fringe.

The reniform spot has a darker posterior outline which forms a straight black line below the cubital vein.

This species is easily identified by its large size, dark gray anterior and lateral margins, and the distinctively shaped reniform spot and postmedial line.