As it infests these foodstuffs, it pollutes them with an unpleasant odour, and intersperses them with a web of silk.

When one caterpillar encounters another, they each produce a small amount of brown liquid from the mouth, and this causes the caterpillars to walk apart. This appears to be a mechanism that prevents overcrowding of the caterpillars. Unfortunately for the caterpillars, this mandibular secretion also attracts parasitoid wasps.

pupa
(Specimen: courtesy of Pauli Tritter, Leamington Spa, U.K.)

The caterpillar typically walks several metres from its foodstuff to pupate in a sparse silk cocoon. The pupa is brown with prominent bulges where the eyes develop.

(Photo: copyright and courtesy of Joyce Gross, Berkeley Natural History Museums, University of California,)

The adult is brown, with a pale basal area on each forewing demarked by a dark line. The hindwings are plain off-white. The moths have a wingspan of about 1.5 cms.

(Photo: courtesy of SNSB, Zoologische Staatssammlung Muenchen, and Centre for Biodiversity Genomics, University of Guelph)

The eggs are white and approximately spherical, with a diameter of about 0.3 mm. The eggs are laid in loose clusters of several dozen especially in crannies and cracks. A female can lay a total of several hundred eggs. The adult females are attracted to lay eggs on larval foodstuffs, especiall those contaminated by wandering fifth instar larvae.

The adults use ultrasonic sounds (~80 Khz) in their courtship behaviour. They also use pheromones (specific sex-attractant substances) the nature of which have been determined. Domestic pheromone traps can be purchased to control the moths. The authors found that these can have an embarrassing effect if used in the home, as some pheromone condenses on clothing. Then when one then walks around a supermarket (where inevitably there will be some of these moths present), rather embarrassingly: they cluster and flutter around one's body.

Attempts have also been made to control the pest using :

drawing by Jacob Hübner,
Sammlung Europäischer Schmetterlinge,
Lepidoptera 8 (1813), Plate 45 (Tinea 5), fig. 310,
image courtesy of Biodiversity Heritage Library, digitized by Ernst Mayr Library, Harvard University.

This species originated in Europe, but now occurs world-wide, for example:

and over the whole of Australia (having been introduced by unfortunate accident) including: Queensland,

Further reading :

Ian F.B. Common
Moths of Australia,
Melbourne University Press, 1990, pp. 57, 68, 350.

Jacob Hübner,
Sammlung Europäischer Schmetterlinge,
Lepidoptera 8 (1813), Plate 45 (Tinea 5), fig. 310.

Peter B. McQuillan, Jan A. Forrest, David Keane, & Roger Grund,
Caterpillars, moths, and their plants of Southern Australia,
Butterfly Conservation South Australia Inc., Adelaide (2019), p. 81.

M.S. Mossadegh,
Inter- and intra-specific effects of the mandibular gland secretion of larvae of the Indian-meal moth, Plodia interpunctella,
Physiological Entomology,
Volume 5 (1980), pp. 165-173.

J.K. Waage,
Arrestment responses of the parasitoid, Nemeritis canescens, to a contact chemical produced by its host, Plodia interpunctella,
Physiological Entomology,
Volume 3 (1978), pp. 135-146.

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(updated 2 February 2010, 5 August 2018, 13 April 2021)