• Latin Name: Pyemotes tritici
  • Latin Family Name: Pyemotidae
  • Common Name: Straw Itch Mite
  • Other Names: Grain Itch Mite

Origin:
Unknown, as the mites are found throughout the world, transported in infested materials with trade and commerce for many centuries.

Biology:
This mite is a paradox. For much of its life it feeds on the larvae of other insects, but when humans come into contact with the medium of the mites and their normal host insects, they will be bitten as well. Since the normal hosts of the mites may be moth or beetle larvae associated with grains or straw used for bedding, when humans are attacked it is referred to as “straw itch”, or also barley, grain, mattress, or hay itch. The effect on bitten humans can be a severe rash and pustules, extreme itching, and fever, all of which may require a month to dissipate. The life cycle is peculiar, with the male often spending its entire life on the distended abdomen of the female as a parasite on her. The mites feed within the host insect larvae and the female’s abdomen enlarges to many times her normal size, which is microscopic when not distended. Within her abdomen may be up to 300 eggs and developing young, which mature to adulthood within the female and then emerge through her genital opening. The male mates with emerging females immediately and new females may produce up to 270 additional offspring.

Identification:
The mites, when not engorged with food, are not visible to the naked eye. The engorged female is about 2 mm long and under magnification resembles a water balloon, with the head and legs sticking out of the greatly expanded abdomen.

Characteristics Important to Control:
Prevention is the major control to avoid bites by these mites. Insect repellents can be worn while in grassy areas or while handling grains, straw, hay, or other dry crops where the mites may be present. Maintaining product free of other insect larvae will reduce the presence of the mites, and fumigation to kill either the insect larvae or the mites will be effective. The symptoms of the mite bites on humans can be reduced with typical antihistamines, bathing in hot water, and other normal anti-itch treatments. The mites cannot continue to breed on humans alone and cannot survive more than 24 hours in a home without finding a suitable host to feed on.