Indian Meal Moth

Brief:

The Indian meal moth, Plodia interpunctella, alternatively spelled Indianmeal Moth, is a pyraloid moth of the family Pyralidae. Alternative common names are North American high-flyer, Weevil moth and pantry moth; less specifically, it may be referred to as ‘flour moth’ or ‘grain moth’. The Almond Moth (Cadra cautella) is commonly confused with the Indianmeal Moth.

Adults are 8 – 10mm in length with 13 – 20mm wingspans. The outer half of the moths forewings is bronze, copper, or dark grey in colour, while the upper half are yellowish-grey, with a dark band at the intersection between the two. The moth larvae are off-white with brown heads. When these larvae mature, they are usually about 17mm long. The entire life cycle of this species may take 30 to 300 days. Female moths lay between 60 and 400 eggs on a food surface, which are ordinarily smaller than 0.5mm and not sticky. The eggs hatch in 2 to 14 days. The larval stage lasts from 2 to 41 weeks, depending on the temperature.

Habits

Adult emergence (eclosion) generally starts in the spring and continues to autumn. Male moths fly readily in response to sex pheromone released by the females. Mating usually occurs on food stacks. Mated females may lay up to 200 eggs over a two-week period. The larvae are able to penetrate even well sealed packaging. Heavy infestations may lead to visible signs such as silk deposits on the edges of stacks. After 5 - 6 moults, larvae will climb to wall/ceiling intersections where only a small proportion of them will pupate immediately, the rest entering a resting phase (diapause), which allows the extended emergence period.

Habitat

The Indian meal moth is usually imported from warm climates in foodstuffs such as peanuts, cocoa beans and dried fruit.

Threats

The Indian meal moth larvae can infest a wide range of dry foodstuffs of vegetable origin, such as cereal, bread, pasta, rice, couscous, flour, spices or dried fruits and nuts. More unusual recorded foods include chocolate and cocoa beans, coffee substitute and cookies. The food they infest will often seem to be webbed together. Infestations at high level can be severely detrimental to product quality.

Prevention

After larvae or moths have been found, it is important to throw out all food sources that are not in very tightly sealed containers. None of the stages of the organism (eggs, larvae, adults) is very temperature-tolerant and all can be killed by a week of freezing or by brief heating in a microwave or conventional oven when such treatment is practical. Nontoxic traps are also available to inhibit the development of adult moths and precipitate their destruction. For example, one type of trap is a triangular box with a lure inside and sticky walls. These traps are generally known as pheromone traps. In this case male moths are attracted inside by the female pheromone (the lure) and then get stuck against the sticky walls inside of the box.

Others

Photos and information are provided by GlobeAustralia.

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