Acarus siro

Acarus siro Linnaeus

(Sometimes known as Tyroglyphus farinae Linnaeus)

Taxonomic placing: Acari, Astigmata, Acaridae.

Common name: Flour mite.

Geographical distribution: Cosmopolitan, common in cool and humid regions, rare in tropical and sub-tropical parts of the world.

Host plants: Feeding on most organic substances, including stored and processed foods, fungi, dead animals and rotting plant parts.

Morphology: The female about 0.3–0.6 mm long, whitish, legs yellow, the external verticals are very short, about a quarter of the internal verticals setae. The anal setae are much longer than most dorsal setae.

Life history: Adult survival, oviposition and egg hatching are best at 20-25ºC and 65-70% relative humidity (RH) or above, the lower temperature limit being at slightly above 0ºC. At 14-21ºC a generation can be completed in 3 weeks, and females raised on wheat germ produce about 250 eggs each and may live for 5-6 weeks.

Economic importance: European Union and U.S. regulations demand zero or near-zero tolerance levels for A. siro infestations in stored products, because this mite is a major pest of stored foods, transmits diseases and is allergenic. It contaminates grains and flour, which acquire unpleasant musty smells and tastes, making them unusable for human consumption. Farm animals given infested feeds eat less, may sicken and their growth is affected. The pest also attacks oilseed rape, linseed and spices, its feeding on the germ resulting in reduced germination. The mite is also an allergen.

Mimolette cheese, produced in Germany, is ripened by the addition of A. siro, whose activities contribute to the flavor and gives the cheese a distinctive, bright orange color.


Monitoring: Mite presence can be detected by various methods, such as the occurrence of “moving” grain dust (which contains the mites), and of a sweetish, musty smell in grain samples. Other methods include ELISA and extraction by various funnels.

Physical control: Total (100%) mite mortality can be obtained by increasing CO2 concentrations in closed containers for 72-96 hours.

Chemical control: Organochlorides and organophosphates were formerly used. Diatomaceous earths are now in more common use.

Biological control: The mites Blattisocius dentriticus (Berlese) (Mesostigmata), and the cheyletids Cheyletus malaccensis Oudemans and Cheyletus eruditus (Schrank) prey on A. siro. A commercial product of C. eruditus, which controls the pest in grain bins, is available in Europe.


Boczek, J.H. and Davis, R. 1985. Effects of alternating temperatures on Acarus siro L. (Acari: Acaridae). Experimental and Applied Acarology 1: 213–217.

Burnett, T. 1977. Biological models of two acarine predators of the grain mite, Acarus siro L. Canadian Journal of Zoology 55: 1312-1323.

Cook, D.A. and Armitage, D.M. 2002. Integrated pest management for stored grain in the U.K. incorporating diatomaceous earths to prevent surface infestations of insects and mites. IOBC Bulletin 25: 221–229.

Eriksson, T.L., Whitley, P., Johansson, E., van Hage-Hamsten, M. and Gafvelin, G. 1999. Identification and characterisation of two allergens from the dust mite Acarus siro, homologous with fatty acid-binding proteins. International Archives of Allergy and Immunology 119: 275-81.

Krizkova-Kudlikova, I., Stejskal, V. and Hubert, J. 2007. Comparison of detection methods for Acarus siro (Acari: Acaridida: Acaridae) contamination in grain. Journal of Economic Entomology 100: 1928-1937.

Melnyk, J.P., Smith, A., Scott-Dupree, C., Marcone, M.F. and Hill, A. 2010. Identification of cheese mite species inoculated on Mimolette and Milbenkase cheese through cryogenic scanning electron microscopy. Journal of Dairy Science 93: 3461–3468.

Navarro, S., Lider, O. and Gerson, U. 1985. Response of adults of the grain mite, Acarus siro L. to modified atmospheres. Journal of Agricultural Entomology 2: 61-68.

Pekar, S. and Hubert, J. 2008. Assessing biological control of Acarus siro by Cheyletus malaccensis under laboratory conditions: Effect of temperatures and prey density. Journal of Stored Products Research 44: 335 -340.

Webster, L.M.I., Thomas, R.H. and McCormack, G.P. 2004. Molecular systematics of Acarus siro s. lat., a complex of stored food pests. Molecular Phylogenetics and Evolution 32: 817–822.

Wilkin, D.R. 1975. The effects of mechanical handling and the admixture of acaricides on mites in farm-stored barley. Journal of Stored Products Research 11: 87–95.

Žďárová, E. and Horak, E. 1990. Preventive biological control of stored food mites in empty stores using Cheyletus eruditus (Schrank). Crop Protection 9: 378–382.