Insects nocturnal

Broad-bordered Yellow Underwing

Noctua fimbriata

A master of mid-summer disguise, the Broad-bordered Yellow Underwing hides a vibrant secret beneath its earthy-toned wings. This large, charismatic moth is a frequent visitor to backyard sugar stations and night-scented flowers.

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Quick Identification

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Size

Wingspan of 45–55 mm (1.7–2.2 inches)

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Colors

Forewings vary from pale olive-green to reddish-brown; hindwings are bright orange-yellow with a distinctively wide black border.

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Key Features

Broad, solid black band on the outer edge of the yellow hindwings
Large, chunky body compared to other yellow underwings
Variable forewing color ranging from clay-colored to deep mahogany
Two distinct spots (orbicular and reniform) usually visible on the upper wings

When You’ll See Them

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Activity pattern nocturnal

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Peak hours 10 PM – 3 AM

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Season June – September

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Diet Adults feed on the nectar of night-blooming flowers like Buddleia and Red Valerian. Larvae are generalist feeders on low-growing plants like docks and primroses, later moving to woody shrubs like hawthorn and birch.

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Habitat Common in suburban gardens, woodland edges, hedgerows, and urban parks.

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Behavior

The Broad-bordered Yellow Underwing is a fascinating nocturnal moth known for its 'flash' defense mechanism. During the day, it rests perfectly still on tree trunks or among leaf litter, where its muted forewings provide excellent camouflage. If a predator disturbs it, the moth suddenly takes flight, revealing a startling burst of bright yellow from its hindwings. This sudden flash often confuses the attacker, giving the moth just enough time to escape to a new hiding spot.

Unlike many other moths that remain active throughout their adult lives, this species often undergoes a period of 'aestivation' or summer dormancy. They typically emerge in early summer, then disappear for several weeks during the hottest part of the season to conserve energy in cool, damp crevices. They reappear in late August and September to complete their life cycle, mating and laying eggs that will hatch into overwintering caterpillars.

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Camera Tips

To successfully capture the Broad-bordered Yellow Underwing on your backyard camera, you should focus on their strong attraction to artificial light sources. Setting up a 'moth wall' using a white cotton sheet and a UV or mercury vapor lamp is the most effective method. Position your camera on a tripod approximately 3 feet from the sheet. Because these moths are large and relatively slow to settle, a camera with a fast shutter speed or a dedicated macro mode will help capture the intricate textures of their forewings.

Baiting, also known as 'sugaring,' is another fantastic way to bring these moths into camera range. Create a thick, fermented syrup using brown sugar, treacle, and a splash of dark beer or overripe bananas. Paint this mixture onto a fence post or tree trunk at eye level. Mount your camera roughly 18-24 inches from the bait station. Since trail cameras are often triggered by heat and motion (PIR), they may struggle to 'see' a moth. Using a time-lapse setting that takes a photo every 30 to 60 seconds is a much more reliable way to ensure you don't miss a visitor to your sugar station.

Pay close attention to the time of year. Because of their mid-summer dormancy, you will see a surge of activity in late June, followed by a quiet period in July, and another major peak in late August. For the best results, aim your camera toward the bait or light on warm, humid, and overcast nights with little wind. On these 'heavy' nights, moths are far more active and likely to descend from the canopy to feed in your garden.

Similar Species

Species that look similar or are commonly confused with Broad-bordered Yellow Underwing.

Large Yellow Underwing

Much thinner black border on the hindwings and a more slender body.

Lesser Yellow Underwing

Smaller overall size with a distinct black crescent mark in the yellow area of the hindwing.

Frequently Asked Questions

These moths are strictly nocturnal, usually beginning their flight about an hour after sunset. They are most active during the middle of the night, specifically between 10 PM and 3 AM.

You can attract them by planting night-scented flowers like Honeysuckle and Evening Primrose. They are also highly attracted to 'sugar' baits made of fermented fruit and sugar, as well as UV light sources.

Adults primarily drink nectar from flowers. The caterpillars are generalists, eating various garden weeds, primroses, and later in their development, the leaves of trees like birch and willow.

Yes, they are very common in suburban environments. They thrive in gardens because their caterpillars can feed on a wide variety of common garden plants and shrubs.

The Broad-bordered Yellow Underwing has a much thicker, solid black band on the edge of its yellow hindwing. The Large Yellow Underwing has a very narrow black line and is generally more elongated in shape.

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