Meal moth
Pyralis farinalis (Linnaeus)

Order: Lepidoptera
Family: Pyralidae
Acronym: PFA

Ecology

The meal moth is found worldwide. It is more common in temperate regions. It is a scavenger and is a minor pest of coarsely-ground cereal products. It is found in grain elevators, mills, processing facilities, warehouses, grain ships and households. It is moderately cold hardy and can overwinter in unheated granaries in Canada’s prairie provinces. It feeds mostly on mouldy grain, decaying cereals and cereal products that have a high moisture content. During the day the adult moths can be seen resting on walls and other surfaces. Resting meal moths fold their wings in the form of a triangle. The adults fly mostly at dusk and dawn.

Damage

The meal moth infests stored products. The larva feeds on wheat, barley, oats, corn, peas and beans, flour, peanuts, dried fruit, potatoes, mixed feed and processed cereals. Damage is not distinct and is caused by larval feeding. When it feeds on whole grains, the larva prefers to feed on the germ and bran. The larva burrows into food and creates silk tunnels in which it will be concealed while it feeds. It produces silk webbing when it feeds and can bind the surface of a grain bulk together. It can burrow through packing. A sign of infestation in the product is contamination with silk webbing, frass, cast skins, pupal cases and adult remains.

Life history

The adult meal moth has a wing span of 15 - 28 mm. The body length is 7.5 - 15 mm. The adult moth is very distinct looking because of its large size and patterned wings. Both the forewings and hind wings are covered in curved dark brown and light brown bands of scales. Two wavy white bands cross the brown bands. Both the forewings and hind wings are rounded at the apex. The labial palps are upturned. The adult does not feed on the commodity. The adults can fly. The meal moth is short lived; longevity is 7 – 21 days.

The female lays between 250 – 500 eggs loosely and randomly on a food source.

The larva is whitish in color. It can grow to 20 - 25 mm in length. It is active. It has a distinct brown head. The first body segment has a black thoracic shield. There are no black spots the body. Ideal conditions for development are temperatures that range between 27°C - 30°C and a relative humidity between 70% - 80%. The development time required for a larva to reach maturity is between from 42 - 56 days. When the larva is mature it actively leaves the food source and searches for a site in which to pupate. The larva pupates in a silk cocoon. Several generations a year can be produced.

Control

Controlling insect infestations

Images

Adult meal moth

Pest and Diseases Image Library, Bugwood.org
Adult meal moth