Montana Field Guide

The Large Yellow Underwing Moth (Noctua pronuba) can have variable coloring. It has brownish camouflaged forewings and bright yellow hindwings with distinct hooked dark markings (Natural England no date).

The last-instar larvae is pale reddish brown dorsally and laterally, and is pinkish brown below the spiracles. The middorsal line is narrow, broken, and bordered by black speckling. There is a subdorsal white line that is most prominant on the anterior half of each abdominal segment. The abdominal segements have black dashes, and the subdorsal area has faint oblique dashes formed by dark speckling that comprises a herringbone pattern. The spiracles are yellow brown. The head is pale yellow brown with darker brown coronal stripes and reticulation (Powell and Opler 2009).

The adults fly from June to October. They roost by day, either on or close to the ground and when disturbed scuttle about wildly, displaying the brightly-colored hindwings. The larvae feed on a wide range of wild and cultivated herbs throughout the winter, spending a lot of time below ground, where they pupate in late spring (Natural England no date).

The larvae feed on a wide range of weedy and cultivated herbs and grasses including Fragaria (Rosaceae), tomato (Solanum lycopersicon var. cerasiforme), Beta (Chenopodiaceae), and Vitis (Vitaceae) (Powell and Opler 2009).