Iris Borer Moth

Iris Borer Moth

Macronoctua onusta
OWLET MOTH FAMILY (Noctuidae)

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The Iris Borer Moth has a wingspan 1.5 to 2 inches. The thorax is black. The forewing is brown with black shading along the costa and the outer margin. The lines and spots are black and thin. The hindwing is plain tan or light gray. The caterpillar is pale pink with a brown head and grows to 1.5 inches. This moth was identified by volunteer experts on the BugGuide website.

 

The Iris Borer Moth is uncommon in Fontenelle Forest and Neale Woods. The individual shown here was photographed at Fontenelle Forest in early October. The adult moths, which are rarely observed, are attracted to lights.

 

This species winters as an egg laid the previous season among old leaves. Larvae hatch in late spring and tunnel into emergent iris leaves. As they grow they move to the base of leaves and hollow out the rhizomes. The larva matures in midsummer and tunnels into the soil to pupate (Reference – “Garden Insects of North America,” Whitney Cranshaw). Adults emerge in late summer and fall.

 

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