The Mediterranean flour moth or mill moth (''Ephestia kuehniella'') is a

moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...

of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Pyralidae The Pyralidae, commonly called pyralid moths, snout moths or grass moths, are a family of Lepidoptera in the ditrysian superfamily Pyraloidea. In many (particularly older) classifications, the grass moths (Crambidae) are included in the Pyr ...

. It is a common pest of

cereal A cereal is a grass cultivated for its edible grain. Cereals are the world's largest crops, and are therefore staple foods. They include rice, wheat, rye, oats, barley, millet, and maize ( Corn). Edible grains from other plant families, ...

grains, especially

flour Flour is a powder made by Mill (grinding), grinding raw grains, List of root vegetables, roots, beans, Nut (fruit), nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredie ...

. This moth is found throughout the world, especially in countries with temperate climates. It prefers warm temperatures for more rapid development, but it can survive a wide range of temperatures. The Mediterranean flour moth is frequently found in warm places with stored

grain A grain is a small, hard, dry fruit (caryopsis) – with or without an attached husk, hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and ...

products, such as

flour mills A gristmill (also: grist mill, corn mill, flour mill, feed mill or feedmill) grinds cereal grain into flour and Wheat middlings, middlings. The term can refer to either the grinding mechanism or the building that holds it. Grist is grain that h ...

and bakeries, where it can breed year round. Flour mills have a particular problem with the Mediterranean flour moth because the

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...

s spin silk that clogs machinery. The most effective pest control strategy for this moth is sanitation of facilities and sealing grain containers to prevent infestation, but some

pesticide Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...

s may also be used.

Description

Adult Mediterranean flour moths have pale gray bodies. Their forewings are gray with black zigzag markings while the hindwings are an off-white color. The wingspan is 1.5-2.6 cm.

Larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e (caterpillars) are white or pink with black spots and dark heads.

Pupa A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...

e are reddish brown. Meyrick - Forewings fuscous, irrorated with whitish and sprinkled with dark fuscous; lines hardly paler, first posteriorly dark-edged, nearly straight, rather oblique, serrate-indented above middle and near dorsum, second strongly indented near costa, dark-edged, with darker dots on veins; two blackish transversely placed discal dots. Hindwings whitish, veins and termen fuscous, in male without whitish ochreous hair-tufts.

Geographic range

First recorded as a pest species in

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

in 1879, the Mediterranean flour moth was found in several locations across

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

in subsequent years. In the late 19th century, roller flour mills caused the moth to become a more widespread pest. It became a common species in

Britain Britain most often refers to: * Great Britain, a large island comprising the countries of England, Scotland and Wales * The United Kingdom of Great Britain and Northern Ireland, a sovereign state in Europe comprising Great Britain and the north-eas ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, and

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

by 1980. The Mediterranean flour moth is now found throughout the world, though it tends to be rare in the

Far East The Far East is the geographical region that encompasses the easternmost portion of the Asian continent, including North Asia, North, East Asia, East and Southeast Asia. South Asia is sometimes also included in the definition of the term. In mod ...

with the exception of

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. Areas of the world with temperate climates are most likely to have infestations of the Mediterranean flour moth in their flour mills.

Habitat

Mediterranean flour moths live in stored grain products. They primarily infest flour, but they can be found in a variety of cereal grains. The moth is a major pest species in flour mills, and it may also be found in

bakeries A bakery is an establishment that produces and sells flour-based baked goods made in an oven such as bread, cookies, cakes, doughnuts, bagels, Pastry, pastries, and pies. Some retail bakeries are also categorized as Coffeehouse, cafés, servi ...

and warehouses, especially in cereal products that have been left undisturbed for an extended period of time. This species particularly enjoys inhabiting flour mills and bakeries due to the heat, which allows it to breed year round.

Food resources

Caterpillars feed on flour, meal, whole grains, and grain residues. Unlike other pest species of moths, ''E. kuehniella'' is almost always found in cereal grain products as opposed to other stored foods such as dried fruit. Adult Mediterranean flour moths are short-lived and do not feed.

Life cycle

''E. kuehniella'' females typically oviposit on the second night after emergence. This is because they require a few hours for the sperm to move from the bursa copulatrix to the vestibulum, where

fertilization Fertilisation or fertilization (see American and British English spelling differences#-ise, -ize (-isation, -ization), spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give ...

occurs. Females will then lay anywhere between 116 and 678 eggs in a food source, such as flour, to which the eggs often become attached. When the eggs hatch, larvae spin silken tubes around themselves. They spend about 40 days maturing within these tubes. Full grown larvae disperse to new locations and spin silken cocoons in which they develop into pupae. Adult moths emerge in 8–12 days. In hot weather, the moth's entire life cycle may take no more than five to seven weeks. Though it prefers warm temperatures because it can develop more rapidly, ''E. kuehniella'' can complete development in temperatures ranging from 12 °C to about 30 °C. ''E. kuehniella'' is also largely influenced by circadian rhythm. Adult emergence most often occurs during the day, while other adult activities, including female calling, male courtship, mating, and oviposition typically occur at night.

Enemies

Parasites

Wolbachia

Mediterranean flour moths are infected by ''

Wolbachia ''Wolbachia'' is a genus of gram-negative bacteria infecting many species of arthropods and filarial nematodes. The symbiotic relationship ranges from parasitism to obligate mutualism. It is one of the most common parasitic microbes of arthrop ...

'', a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

that affects the reproduction of its host species. These maternally-inherited bacteria cause

cytoplasmic incompatibility Cytoplasmic incompatibility (CI) is a mating incompatibility reported in many arthropod species that is caused by intracellular parasites such as ''Wolbachia''. These bacteria reside in the cytoplasm of the host cells (hence the name ''cytoplasmic ...

in ''E. kuehniella'', which means that sperm and eggs cannot join to form a viable

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

. Infected males produce sperm that is only compatible with eggs from infected females, resulting in a decrease in fitness for uninfected females. Different strains of ''Wolbachia'' cause different levels of cytoplasmic incompatibility.

Nemeritis canascens

''E. kuehniella'' is parasitized by ''Nemeritis canascens'', a parasitic wasp of the family

Ichneumonidae The Ichneumonidae, also known as ichneumon wasps, ichneumonid wasps, ichneumonids, or Darwin wasps, are a family of parasitoid wasps of the insect order Hymenoptera. They are one of the most diverse groups within the Hymenoptera with roughly 25 ...

. The larvae of this wasp are

endoparasites Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

of the moth during the moth's larval phase. Larvae of ''Nemeritis'' feed on the blood of the host caterpillars. ''Nemeritis'' remains in its first instar until the host caterpillar is in its last instar of development. The parasitic larvae feed more quickly as the host caterpillar gets older, accounting for rapid development in late final-instar caterpillars and delayed development in first instar caterpillars. The changing rate of feeding in the parasite is attributed to the changing composition of the host blood on which it feeds.

Mating

The maturation of both male and female reproductive systems occurs soon after emergence. Adult moths commonly mate on the day of emergence, which maximizes the reproductive success of females. Female calling and male courtship behaviors peak just prior to peak mating—these behaviors are useful in successful mating. The Mediterranean flour moth is a

protogynous Sequential hermaphroditism (called dichogamy in botany) is one of the two types of hermaphroditism, the other type being simultaneous hermaphroditism. It occurs when the organism's sex changes at some point in its life. A sequential hermaphrodit ...

species, so females emerge significantly earlier than males. This mechanism may be used to reduce inbreeding, as females will emerge and mate with other males prior to their brothers emerging. The optimal mating time for females is on the same day they emerge, because fertility decreases when mating occurs later. Females release pheromones as a type of calling behavior to demonstrate to males when they are most fertile. In a study of the effects of food shortage and larval crowding on male reproductive phenotype, it was found that males who emerged as adults from the population with the most crowding had smaller forewings, thorax, and head, as well as a lower body mass. It is worth noting, however, that these smaller males had larger forewings relative to their body mass. It is suggested that this may be beneficial in terms of mate searching at higher densities by promoting their dispersal. It was also found that while mating frequency did not seem to be affected by larval density, those from higher densities had a shorter adult lifespan and produced fewer eupyrene sperm. In order to increase their reproductive success at higher densities, and thus at higher levels of sperm competition, males maintain apyrene sperm production and mate more at a higher frequency. ''E. kuehniella'' is a

polyandrous Polyandry (; ) is a form of polygamy in which a woman takes two or more husbands at the same time. Polyandry is contrasted with polygyny, involving one male and two or more females. If a marriage involves a plural number of "husbands and wives ...

species.

Interactions with humans

Pest of stored grains

Larvae will attack stores of flour or other cereal grains as a source of food, but the most damage is done when they interfere with machinery in the mills. The web-like material that larvae spin clogs machines. Grain mills have had to shut down due to this issue. They also cause damage by biting holes in silk screens used to sift flour.

Pest control

Prevention

The most effective pest control method for the Mediterranean flour moth is preventing it from infesting stored grains. This involves basic

sanitation Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation systems ...

practices such as thoroughly cleaning out bins and surrounding areas of the floors and walls to remove old grains and particles of dust. Sealing all cracks and crevices in the building and grain bins can prevent moths from entering. Checking grain bins frequently (especially in warm months) for hot spots,

mold A mold () or mould () is one of the structures that certain fungus, fungi can form. The dust-like, colored appearance of molds is due to the formation of Spore#Fungi, spores containing Secondary metabolite#Fungal secondary metabolites, fungal ...

, and insects can also reduce risk of infestation. Sanitation is generally the preferred strategy for preventing Mediterranean flour moth infestation.

Pesticides

Insecticide Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...

s are sometimes used as well as

fumigants Fumigation is a method of pest control or the removal of harmful microorganisms by completely filling an area with gaseous pesticides, or fumigants, to asphyxia, suffocate or poison the pest (organism), pests within. It is used to control pests ...

if infestation has already occurred. Both of these pest control options involve

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...

chemicals and require safety precautions to use.

Methyl bromide Bromomethane, commonly known as methyl bromide, is an organobromine compound with chemical formula, formula Carbon, CHydrogen, H3Bromine, Br. This colorless, odorless, nonflammable gas is Bromine cycle, produced both industrially and biologically ...

was commonly used as a pesticide in several countries, but was later banned for environmental reasons when it was classified as an ozone depleter.

Biological control

Trichogramma ''Trichogramma'' is a genus of minute polyphagous wasps that are endoparasitoids of insect eggs. ''Trichogramma'' is one of around 80 genera from the family Trichogrammatidae, with over 200 species worldwide.Consoli FL, Parra JRP, Zucchi RA (20 ...

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

s are a potential biological control for the Mediterranean flour moth, because they can kill the host in the egg stage, before it reaches the destructive larval phase. The success of ''Trichogramma'' in biological control programs is influenced by host diet and the resulting nutritional quality of the eggs. Temperature can also impact host suitability for the parasitoid.

Irradiation

Gamma radiation A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

is another control that has been considered as an alternative to pesticide use. Low-dose

irradiation Irradiation is the process by which an object is exposed to radiation. An irradiator is a device used to expose an object to radiation, most often gamma radiation, for a variety of purposes. Irradiators may be used for sterilizing medical and p ...

has been approved by the

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

as a safe pest control measure in foods. This method is fast and not temperature dependent. Irradiation treatment can prevent adult emergence or introduce

sex-linked Sex linkage describes the sex-specific patterns of inheritance and expression when a gene is present on a sex chromosome (allosome) rather than a non-sex chromosome (autosome). Genes situated on the X-chromosome are thus termed X-linked, and a ...

lethal mutations that cause inherited sterility.

Gallery

File:Ephestia kuehniella female dorsal.jpg, Female, dorsal view File:Ephestia kuehniella female ventral.jpg, Female, ventral view File:Ephestia kuehniella male dorsal.jpg, Male, dorsal view File:Ephestia kuehniella male ventral.jpg, Male, ventral view File:Ephestia kuehniella larva.jpg, Larva File:- 6020 – Ephestia kuehniella – Mediterranean Flour Moth (21710969424).jpg, Dorsal view, wings closed

References

External links

{{Taxonbar, from=Q1130463 Household pest insects Storage pests Phycitini Moths described in 1879 Moths of Japan Moths of Europe Moths of New Zealand Moths of Asia Moths of Iceland Endoparasites