Investigating the Noctua pronuba or Yellow Underwing Moth

The Noctua pronuba, also known as the Yellow underwing moth, is known for its bright orange hindwings. It is a pest that destroys economically important crops around the US.

Noctua pronuba Moth Species Summary

Scientific NameNoctua pronuba
Family NameNoctuidae
HabitatLawns, open areas with some weedy growth
RangeNorth America and Europe
Host PlantsWeedy and cultivated herbaceous plants
Butterfly DescriptionBrown wings with orange-yellow hindwings
Caterpillar DescriptionThe lower part of the body is greenish, upper part has two rows of black dashes

noctua pronuba Description

The Large yellow underwing moth is also known by its common name, the Yellow underwing moth. It has a wingspan of about 1 inch (2.1 to 2.6 cm), which is quite large for a noctuid moth. Its forewings are brown with prominent black dots close to the apex.

The transverse lines are darker and visible on the pale light brown background. Its hindwings are bright orange with a blackish-brown marginal band but miss a discal spot. The orbicular spot is large, light brown, with a pale grayish filling.

noctua pronuba vs. Noctua comes

In some cases, Large yellow underwing moths can be confused with Lesser yellow underwing (Noctua comes), usually found in the western part of the Pacific Northwest. Noctua comes has a large black discal spot on the dorsal hindwing, while Noctua pronuba lacks it. Like with many other butterfly and moth species, the wing coloration serves to confuse predators.

Is Noctua Pronuba a Butterfly or a Moth?

Noctua pronuba is a moth, but it’s also called the Large yellow underwing butterfly. This species is also the most abundant large moth in the Palearctic area.

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Larva And pupa Description

Noctua pronuba larva
Noctua pronuba larva

Noctua pronuba caterpillar is green or brown and has two rows of black dashes on its back. This larva, known as the cutworm, causes fatal damage to many herbaceous plants, often cutting them off completely. Larvae overwinter and eat during the mild days of the winter.

Pupae come in chestnut-brown. They’re smooth, shiny, and about an inch (2.5 cm) long. Pupae have several spines and a pair of bristles.

Noctua pronuba Moth Lifespan

Egg Stage14 to 28 days
Caterpillar Stage10 to 20 days
Chrysalis Stage7 to 14 days
Butterfly Stage365 days
Typical Duration of the Noctua pronuba Lifespan

Host Plants and diet

Common host plants of the Large yellow underwing are:

  • Plantain
  • Grasses
  • Dock
  • Marigold
  • Daisy
  • Butterfly bush
  • Carnation
  • Wild tobacco
  • Primrose

Larvae are often found in the soil next to the host plant’s roots. They’ll attack the root system and feed off the plant’s leaves. In case you wish to attract these moths to your garden, plant carrots, strawberries, tomatoes, or marigolds.

Additionally, the Large yellow underwing butterflies are polyphagous — they feed on economically important crops. The larvae eat both cultivated and wild food plants and the early stages of seedlings of various trees and shrubs. For example, its favorite herbaceous plants include:

  • Beet
  • Brassica
  • Marigold
  • Chrysanthemum
  • Dahlia
  • Carrot
  • Carnation
  • Strawberry
  • Freesia
  • Gladiolus
  • Hawkweed
  • Lettuce
  • Tomato
  • Plantain
  • Grasses
  • Primula
  • Rhubarb
  • Nightshades (potato and tomato plants)
  • Spinach
  • Dandelion
  • Sweet violet
  • Grape

Are Noctua pronuba pests?

Due to their food source requirements, the caterpillar of this moth is known to be a pest. It’s causing fatal damage to all herbaceous plants, and most people don’t want it near their crops or gardens.

In the fall of 2007, many of its caterpillars were found in central and northern Michigan, with thousands infesting homes and hay fields. Being the winter cutworm, this moth’s larva can cause severe damage to agriculture. Luckily, many insecticides help control this moth species and protect the crops.

Behavior and flight

This moth is attracted to light, often in huge numbers. They also like nectar sources. Adults are around from June onwards, with a peak in activity in August. During the day, they’ll rest in the shelter of leaves and dead grass. Adults fly rapidly and erratically for a short distance; then, they’ll resettle.

Females deposit eggs in large batches on various plants. However, before that, they have a pre-oviposition period lasting for a month. Once hatched, larvae will feed from mid-summer/early autumn and become fully adult in the following spring. Larvae will pupate in the soil in the late spring, and adults will appear a few weeks later.

Habitat, distribution, migration

This moth likes lawns and open areas. It’s present in large quantities around open grasslands, oak savanna, woodlands, and urban areas at low elevations. Its habitat also includes undisturbed meadows at higher elevations. Noctua pronuba moth is often a competitor with native moths and butterflies.

Dry, open ponderosa pine forests, juniper woodlands, and disturbed agricultural areas are also its favorite places. This species shows great ecological plasticity.

This moth species is migratory and tends to suddenly appear around the marginal parts of its range, which includes Europe, Central Asia, North America, and North Africa.

Common Predators

The most common predators of this moth are the Greater horseshoe bat (Rhinolophus ferrumequinum), Lesser horseshoe bat (Rhinolophus hipposideros), European species of flies, and Brown long-eared bat (Plecotus auritus).

Some parasites that attack these moths are flies in the family Tachinidae (Blondelia nigripes, Ramonda spathulata, Wagneria dilatata), spongy moths named Lymantria dispar (Compsilura concinnata) and European species of flies (Eurithia caesia).

Are Noctua pronuba caterpillars poisonous?

More research needs to be done regarding the toxicity of these caterpillars. There were some instances where domestic pets ingested large larvae and got sick. Still, most caterpillars of this species will hide during the day to avoid predation.

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