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Mystery Bites in Southeast Kansas
Updated on 18 April 2007

Caused by Pyemotes mites (pronounced "pie uh moat eez")

Quicktime movies of mites are available below.

In late August 2004 a rash of “mystery bites” erupted when many people attending a Pittsburg State football game came down with what appeared to be chigger bites. The problem was that they didn’t conform to the typical chigger bite distribution around socks and belt lines. For a while it appeared that biting midges or "no see-ums" might be the culprit. As I told the college newpaper reporter when nobody knew what was causing the problem, it was a real “science project.” It turned out to be a real CSI story, not a Hollywood version.

To make a long and interesting story short, the county health department enlisted help from State Health Department, entomologists from Kansas State University and epidemiologists from the Centers for Disease Control and Prevention. The biting also turned out to be happening in Missouri, Oklahoma and Nebraska. Entomologists at the University of Nebraska discovered that a mite in oak galls was causing the problem in their area and passed the work on to K-State entomologists. I helped sleuth out the culprit in Pittsburg by collecting samples, offering professional opinions, and working with the K State and CDC teams. Yes, I did get bitten every time I went sampling for them. Hundreds, if not thousands, of people were bitten over several weeks. The Morning Sun and Collegio wrote several articles and a local TV station was innundated with calls when they did a news story. Eventually the biting subsided as cool weather brought relief, but another smaller episode occurred as people cleaned up fallen leaves.

It seems that we had a bumper crop of midges that make galls on pin oak leaves this summer, probably due to unusually cool weather and rain. As a result, the predacious mites that normally eat these midges had a population explosion that literally spilled over onto us out of the trees. This helps explains why so many bites were on necks and shoulders, but also on legs since many would have fallen to the ground. The mite that seemed to be causing the bites was initially identified as the the straw itch mite (Pyemotes tritici). Then, after mite identification specialists examined it more closely it appeared that Pyemotes herfsi, a European mite that had been introduced into the U.S. and was just now discovered because of this outbreak. On closer examination of the specimens and the history of mite outbreaks in the U.S., mite experts now considering the possibility that Pyemotes herfsi was introduced to North America some time ago. It will require DNA analyses and breeding experiments to determine this with certainty.

There were several types of galls on pin oak leaves and other predatious mite species were found in some of them, so additional mite species may be involved as well. Research into the midges and mites is planned for this year.

How can I tell if I've been bitten by these mites? I have been getting questions from people who want to know if Pyemotes mites are responsible for their bites. Here's what I generally can say about it.

A paper has been published about the outbreak.

Broce, Alberto B, Ludek Zurek, James A. Kalisch, Robert Brown, David L. Keith, David Gordon, Janis Goedeke, Cal Welbourn, Jon Moser, Ronald Ochoa, Eduardo Azziz-Bungartner, Fyuen Yip, and Jacob Weber. 2006. Pyemotes herfsi (Acari: Pyemotidae), a Mite New to North America as the Cause of Bite Outbreaks. Journal of Medical Entomology. 43(3): 610-613.


Quicktime movie of Pyemotes mites in a midge gall.

Quicktime movie of another mite inhabiting round galls on oak leaf.

Quicktime movie of mites inhabiting flattened gall with many chambers for host insects.

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


Typical bites (several days old) on neck.

Close-up of bites on neck.

Bite next day after exposure.

Detail of bite next day.

Vessicle with clear fluid formed on bite after about 2 days.

Bite after vessicle has formed scab.

Typical bites inside of arm at elbow after about 10 days.

Bites and rash on inside of elbow.


C-shaped marginal gall opened, exposing two yellowish midge larvae being eaten by mites. Round objects are female mites filled with developing offspring.


C-shaped marginal gall opened, exposing gravid female mites. Midge larvae have been completely consumed. White marks are one millimeter apart.

Several types of galls on newly forming pin oak leaf.

C-shaped midge galls newly forming on margins of new pin oak leaves (April).

C-shaped midge galls truning red on new leaves (May).

Browning C-shaped midge galls on pin oak leaves in fall (September).

Vein galls on pin oak leaf veins in spring (April)

C-shaped marginal and vein galls on dead pin oak leaf on ground in fall (October).

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