''Macronoctua onusta'', the iris borer, is a species of cutworm or dart moth in the family
Noctuidae
The Noctuidae, commonly known as owlet moths, cutworms or armyworms, are a family of moths. They are considered the most controversial family in the superfamily Noctuoidea because many of the clades are constantly changing, along with the othe ...
. It is found in North America.
[
The MONA or Hodges number for ''Macronoctua onusta'' is 9452.][
]
Description
''Macronoctua onusta'' is a large brown and smoky dark gray moth (FW length 18–21 mm). It has a forewing
Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments (the mesothorax and metathorax), and the two pairs are often referred to as the forewings and hin ...
that is broad with a scalloped outer margin and a black streak along the reniform spot. 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 antemedial and postmedial lines are thin, dark gray. The antemedial line is drawn far lateral above the posterior margin. The median line is dark brown, strongly arched toward across the brown median area below the cell. The postmedial line is jaggedly zigzagged on the anterior wing and straight from Anterior cubitus vein to the posterior margin. The subterminal line is only evident as the transition from the brown subterminal area to the black terminal area. The terminal area is a black line. The three spots are outlined in thin black. The orbicular spot is a small oval. The reniform spot has a darker posterior outline which forms a straight black line below the cubital vein. It is large and asymmetrically kidney-shaped with the lower end curved toward the outer margin touching the postmedial line. A spike-like process extends toward the base from the posteromedial end. The claviform spot is small and elongate with a rounded end. The hindwing is dirty brown-gray with slightly darker discal spot and veins, and scalloped terminal line. The hindwing fringe is light gray with a brown base. The head and thorax are even smoky dark gray. The male antenna is broad and bead-like.
This species is easily identified by its large size, dark gray anterior and lateral margins, and the distinctively shaped reniform spot and postmedial line. Similar dark brown moths lack the dark posterior outline and spike from the medial reniform spot and the postmedial line with serrate anterior and straight posterior segments.
Life History
* Larvae - This species is a foodplant specialist that bores into the rhizomes of irises (Iris spp.) in the Iridaceae.
* Adults - Adults fly in the fall, usually in September and October. It comes to lights, although not particularly well. Forbes (1954) comments that the moth is best obtained by rearing.
References
Further reading
*
*
*
Noctuinae
Articles created by Qbugbot
Moths described in 1874
Moths of North America
{{noctuinae-stub