The Tetranychidae are usually occurring on plants except for diapausing females. Did you check your specimens after mounted on slides?

Carlo

Hi Mahran,

Several authors have reported tetranychoid mites "from soil" (e.g. our colleague Mohammad Khanjani) but these are usually thought of as mites from low-growing plants collected with the soil. As Carlo notes above, spider mites can have diapausing females, but I'm unaware if any "over-summer" in hot, dry climates (or are nocturnal? or group together after host plants are harvested/die?). If your mites were aggregating, then perhaps something interesting like this is going on, but they will also have a host plant, of course.

Some Tuckerellidae are associated with roots, and I think  linotetranids might be suspected of the same, as are allochaetophorids (see Meyer & Ueckermann 1997 on these). Considering these families include sister groups to the Tetranychidae and Tenuipalpidae, then perhaps we can expect some root-feeding spider mites or flat mites too: that would be a nice find!

As Carlo notes, it would be good to get a genus identification on them. That should at least give some clues: for example, Petrobia harti is common on oxalis, and Petrobia latens would be expected in wheat fields, and in the right habitat I'd expect both to turn up in soil every now and then.

Kind regards, Owen.

First: thank you for both answers.

i noticed this mite on plant with one or two individuals (please check 1st photo). no feeding symptoms noticed on this plant.

After that i could notice it down surface of stone. next to that plant (please check 2 nd photo). number of mite was very high. 

later i could see this mite associated with every stone in that area.

Collection area is dry and none cultivated area with very less covering plants. 

All characters of this mite fitting to Tetranychidae subfamily Bryobinae. 

thanks for all comments 

mites photos on stone

Interesting, I have not come across any tetranychid  in the soil, as Seeman says can they be P, latens, summer eggs are laid by these in the soil, which hatch around November  to infest wheat and several other plants, this happens in Punjab and few north Indian states.

Hi Mahran,

In addition to the cases reported by Carlo and by Owen the only one spider mite I found walking and staying (!) on the soil quite far from possible host plants (and that seemed to be healthy) belongs to the genus Aplonobia. We found some specimens of Aplonobia histricina that have this type of behaviour particularly when they lay clustered diapausing (?) eggs. In this case they are able to run for a few meters from their possible host plant and they lay eggs on any piece of wood/bark found on bare ground. Then they are able to walk around like bodyguards and seem to fast as no food source is available in the immediate vicinity. Several specimens can be found together having this behaviour in a reduced inhospitable area.

Kind wishes,

Philippe

Did you locate any other stages? If it is a colony try them rearing. Usually plant associated spider mites like Petrobia are known to hibernate in soil near their host plants. Why dont you see any xerophytes near the stones. I will also search the literature and let you know.