Large yellow underwing

📖Overview

Noctua pronuba is a very common noctuid moth native to Europe, North Africa and parts of Asia and introduced widely to North America. Adults fly at night and are strongly attracted to light. The species is adaptable and occupies many habitats from gardens and farmland to woodland edges. Larvae are generalist feeders known as cutworms and can damage grasses, vegetables and crop seedlings.

The species is easily noticed when disturbed because the resting forewings are cryptic brown but the hindwings flash bright yellow-orange in flight. It usually has a single generation per year in northern Europe, and it overwinters as a caterpillar that feeds on mild nights.

🔍How to identify a large yellow underwing

Adult wingspan about 40-60 mm. Forewings are variable shades of brown to reddish-brown with darker markings and sometimes a pale reniform (kidney-shaped) spot. Hindwings are bright yellow to orange with a broad blackish-brown terminal band; the contrast is a key field mark. The body is robust and hairy. Caterpillars are smooth or slightly hairy, grey to greenish or brown, with a pale dorsal line and dark head; they reach around 35-45 mm when fully grown.

1. Look for bright yellow-orange hindwings with a narrow black band near the edge and no dark crescent mark in the center, visible in flight
2. Forewings are variable brown or reddish-brown, usually with a small black mark near the wingtip on the leading edge
3. Large size for a noctuid: wingspan about 40-60 mm and a robust body

Lookalikes

↻Life cycle

1. 🥚

   Egg

   Females lay clusters or scattered eggs on grasses and low plants; eggs hatch in about 1-2 weeks depending on temperature.

2. 🐛

   Larva (cutworm)

   The caterpillar stage is a ground-feeding generalist that chews leaves and can sever seedlings at soil level; it feeds slowly through autumn and winter on mild nights and completes growth in spring.

3. 🫛

   Pupa

   Pupation occurs in a fragile cocoon in the soil in spring.

4. 🦋

   Adult (moth)

   Nocturnal flyer that emerges from the pupa; adults mate and females lay eggs, producing one or more generations per year depending on climate.

🍃Diet and predators

🌱Effect on plants and gardens

Larvae feed on a wide range of herbaceous plants, grasses, vegetable seedlings and young crop plants; in large numbers they can cause damage to lawns, vegetables and cereals.

How to get rid of large yellow underwings

Monitor gardens for young caterpillars and handpick at night or early morning. Use barriers or collars around vulnerable seedlings. Encourage natural enemies (birds, ground beetles, parasitic wasps). For heavy infestations, targeted biological insecticides containing Bacillus thuringiensis kurstaki (BTK) can be effective on young caterpillars; follow label instructions. Chemical insecticides are effective but use as a last resort and follow local regulations.

📍Where and when to find it

Adults at porch or street lights, near flowering plants or fermenting fruit at night. Larvae at ground level feeding on grasses and seedlings; look under debris, at base of plants or in soil.

✨Fun facts

• First recorded in North America in Nova Scotia in 1979, it has since spread across much of the continent.
• The sudden flash of yellow-orange hindwings when it flies is a startle display to confuse predators.
• Caterpillars are often active at night and hide at the base of plants or in the soil during the day.

?Frequently asked questions

📷Photos of the large yellow underwing