Common Name: Straw itch mite
Scientific name: Pyemotes tritici (La Grèze-Fossat & Montane)
Description: Soft-bodied, almost microscopic (1/125 to 1/16 inch). They have four pairs of legs, with the first two spaced far apart from the last two.
Life cycle: Mated females attached to man or insect hosts enlarge to 1/16 inch, with greatly-distended abdomens containing eggs and developing young. Up to 300 adult mites develop inside the mother and mate soon after leaving the female. These adults seek a host, and produce another generation within a week.
Habitat and food source(s): Mouthparts are irritating with reduced stylet-like chelicerae and injection of salivary fluids. Straw itch mites parasitize a wide variety of insects, including stored grain pests (e.g. Angoumois grain moth, Sitotroga cerealella (Oliver), and others). They are, therefore, considered to be natural enemies of arthropod pests.
These mites are cultured on caterpillar-infested wheat seeds and sold commercially for application to fire ant mounds.
Pest status: Considered natural enemies of arthropod pests. Although occasionally sold as a biological control agent for the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), it is historically known for medical importance because it is capable of causing rashes to humans. They are also known as “hay” or “grain itch mites.” Humans, particularly in grain growing areas, handling infested straw, crops (beans, cotton, small grains) or crop residues can be severely affected. Symptoms are similar to those caused by chiggers and develop into a hive-like rash over much of the body. Intense itching can last a week or so, and may be accompanied by fever, headaches, mild diarrhea, vomiting and joint pain.
Literature: James & Harwood 1979; Metcalf et al. 1962.Reviewed Olson 11/96.