''Pyemotes tritici'' is a species of

mite Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...

known as the grain itch mite or straw itch mite. It is a

cosmopolitan Cosmopolitan may refer to: Food and drink * Cosmopolitan (cocktail), also known as a "Cosmo" History * Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953 Hotels and resorts * Cosmopoli ...

species that is found on straw, hay and stored grain. It is a parasite of small arthropods and is being investigated as a possible biological control of stored product pests. It is associated with

dermatitis Dermatitis is inflammation of the skin, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened. The area of skin involved can v ...

in humans, and it causes an itchy rash.

Life cycle

''Pyemotes tritici'' is

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

, this means that the embryos fully develop inside the female, emerging from the birth canal as adults. Males are born after a gestation period that is two days less than that of the females, the males help the females to emerge and copulation takes place as soon as the females are born. In fact any unmated female is unable to copulate later in life. Fewer than 10% of the offspring are male, although the proportion rises under conditions of gross overcrowding. On average, each female produces about 250 offspring, but after mating with about fifteen females, male fertility rates decline.

Ecology

''Pyemotes tritici'' is a

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

of arthropods. The females puncture the host with her stylet, injecting a toxic venom that paralyses the host, which eventually dies. The Angoumois grain moth (''Sitotroga cerealella'') is a pest of stored grain, laying its eggs on the seedheads in the field or on the grain in the silo. Until 1882, it was thought that ''Pyemotes tritici'', which is sometimes found swarming over stored straw or hay, was feeding on the crop, however it turned out that the mites are carnivorous and are feeding on the larvae of the moth and other insect pests. When the mites come into contact with human skin, they attempt to feed there, causing an intense itchiness, often over the whole body surface. After about sixteen hours, blister-like vesicles erupt on the skin surface and other symptoms can include headache, joint pain, fever and nausea.

Use in biological pest control

The mite is being investigated as a potential

biological pest control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...

agent for stored product pests; its high rate of population growth is likely to exceed that of its host arthropod, and it has been found possible to mass rear it in the laboratory.

References

{{Taxonbar, from=Q4358226 Trombidiformes Animals described in 1851