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Could Pyemotes Mites Be Biting Me?

Updated on 18 May 2005

Pyemotes mites (pronounced "pie uh moat eez")


If you are having reactions that look like the pictures on my web site and the others linked to it, I would suspect some kind of mite being involved.

When you start looking, you find that there is not a lot of information available that will help pinpoint the culprit. It took us several weeks to make the link to the mites we found in oak galls. I was convinced that mites were involved from the beginning, but others suspected biting midges - cousins of mosquitoes. The vessicle formed from some bites is typical of a chigger bite, but chigger bites are distributed differently over the body.

However, there are lots of different kinds of mites. In Kansas alone there are almost 50 kinds of chiggers, but only one species commonly bites humans. Of course some of the others may bite humans under unusual circumstances. These are predacious mites that usually feed on insects or other animals. As it turned out, it was a Pyemotes mite and the straw itch mite has been known to bite humans and cause outbreaks in the past. Again, this is under unusual circumstances- you have to be in the wrong place at the wrong time. More detailed investigation showed that the mite was not the native straw itch mite, but a mite that was previously only known from Europe. So it appears to have been introduced to the U.S. some way and unusual weather probably led to an outbreak in this region. There may have been outbreaks in the past in Colorado and Kansas City that were attributed to a different species. It is not easy to identify these things and experts are trying to determine if those past outbreaks were caused by the same mite we have here.

The chances of finding a mite on a bite is slim to none. A local vet had many pet owners visit him during the fall with the bites. He understands mites and took scrapings from the people just as he would from dogs or cats to look for mites. He found none. Our experience was the same. The mite is most likely long gone by the time you get the reaction. The reactions range from reddening to a vessicle forming, then scabbing over. Most bites itch, the vessicated and scabbed bites itch intensely and demand that you apply some ointment that will numb the area to reduce itching and scratching. Scratching does not usually produce relief, but actually hurts. Scratching leads to more damage and potential infection. It is not a good idea to scratch. Itching and other symptoms last 10 - 14 days or more. Pyemotes mites inject a toxin that some people have allergic reactions to.

It was not easy to make the initial connection between the bites and the leaf galls. People were getting bites and thinking they were from infestations in the college dorms, from flying insects at football games, from flying insects near ponds/ lakes, etc. Researchers at the University of Nebraska made the connection to the galls, told us about it, and when we looked, we confirmed their findings. After that, it all fit together and made sense. Prior to that none of the connections we suspected could be traced to a biting culprit.

Pyemotes herfsi mites have been found in leaf galls formed on three species of oaks [pin oaks, red oaks, and black oaks]. They are not found on burr oaks. We plan to survey next year to see if they are on other related oak species or other hosts plants reported for earlier outbreaks. Virtually nothing is known about the mites or the midges beyond the basic life cycle. Next year we hope to determine when the midges begin making galls and the mites begin infesting the galls, and some details related to how they do this. We suspect that the outbreak was connected to unusual weather last summer that led to a bumper crop of gall midges and subsequently the mites. If this is the case, there may not be a population explosion next year and we may not be able to find many mites at all. On the other hand, if this is a newly established mite population, it may present a continuing problem and spread to other areas next year [in the way that West Nile Virus has become established and has spread in the U.S.]. We won't know the answer to that until next year.

Mites can be found within galls on dead leaves still clinging to trees, and leaves that have fallen. After the biting subsided with the onset of cold weather, reports of biting increased when a warmer spell occurred in the late fall and people were raking leaves. Examination of galls in December and January also revealed that some mites are still alive. An outbreak of straw itch mites in the U.S. in the early 1900's resulted from infested straw being used for fresh bedding. People using those beds were bitten intensely. Live mites in infested leaves back yard in December suggests that, if you stuffed a mattress [or dog bed] with those leaves and brought it in the warm house, you could potentially be bitten by mites while it is freezing outside.

So, can you connect what you think are bites to those mites? You will need to do some sleuthing like we did. Does your condition really look like a mite bite? Look at the photos and descriptions. Do you ave a distinct red swelling with a vessicle contining clear fluid? Do you have oak trees/ leaves in your yard/ neighborhood? Could another mite be involved that has a different life history? Coul another biting insect (such as bed bugs) or arthroopod (spiders) be involved? Other arthropods typically have slightly different symtoms and signs that must be considered by an expert to distinguish them. You should contact your County Cooperative Extension Service and have them look into your circumstances. They should have an entomologist. If they are not aware of the Pyemotes outbreak and want information, direct them to my web site, the Kansas State University web site, or the University of Nebraska web site for information [there are links from my web site].

Not a very definitive answer for your problem, but I can't really say much more based on what you have told me. I hope this helps.

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More information is available at the following links: Kansas Insect Newsletter

Kansas State University Research & Extension News

University of Nebraska Cooperative Extension

U. Nebraska Lincoln