My math seems to have been off when I first figured the size of these tiny creatures. Dividing the length of the mite by the hieght of the numeral 2, then multiplying times 3.2mm (the measured length of the numeral 2) I get 0.22mm, less than half my original 0.48mm.

The mites might actually be smaller since the angled view of the numeral 2 makes it appear smaller that it is. This factor is to some extent offset by the angle of the mite but my guess is that the mite's length is less distorted than the size of the numeral 2.

Moved from Mites and Ticks.

I comment upon series of pics entitled "tiny white riders" (image 55502) and " Whatzit-covered bostrichid - Xylobiops basilaris" (image 55443).

Those tiny bugs are mites of a subcohort Heterostigmata, almost certainly of a family Tarsonemidae. They are phoretic. i.e. they are just "riders", not parasites. In fact, those are adult females (not juveniles), typically for tarsonemids their hind (4th) legs are somewhat reduced, and thus hard to see at certain angles.
"Either those are antennae or a very spindly pair of front legs held at a very antenna-like angle" - second option wins; indeed they walk keeping their front legs erect and occasionally probing environment. As the 4th pair can only be passively dragged behind, and 1st is up off the ground, they effectively use only four of eight legs for walking!

I do congratulate you on nearly the best pictures that can ever be done. Heterostigs are one of smallest arthropods on Earth, and with this magnification depth of field and sharpness drop unavoidably.

Your finding of those mites coincides with my current occupation, i.e. tarsonemids associated with bark beetles and wood borers. So, I would be most grateful if you can send me specimens for research.

Dr. Wojciech Magowski
Department of Animal Taxonomy and Ecology
A. Mickiewicz University
Poland

Moved from Mites.

These are most certainly mites, possibly juvenile ones, some of which can have only six legs. Moving to Acari page.