It just mite be.
What is the size of a pencil dot, can climb walls, enter through screens and leave red stains if crushed? The answer is clover mites.
Clover mites are very tiny mites (about 0.75 mm) that are usually reddish in colour but can also be olive green or rusty brown. Their first pair of legs are very long and are held forward so that they resemble antennae. The immature stages of clover mites are bright red.
Clover mites are strictly plant feeders. They feed on about 200 different plants, including trees, shrubs, flowers, grasses and various crops. They are often associated with heavily fertilized lawns. Infestations usually occur in the spring and fall, as clover mites prefer cooler weather with ideal temperatures in the 18-20 degrees C range. They become inactive during hot, dry weather.
These mites are found on exterior foundations, walls, rocks, and patio stones and on interior windowsills, floors, curtains and counters. It is their presence and not damage to plants or grasses, which is the main cause of concern. Clover mites do not bite people or pets. Because they are so small, they are able to penetrate through tiny gaps around windows and doors, cracks and crevices and make their way into the house. They often become noticeable when they are on a light coloured background. If crushed, they will leave stains on drapes, carpeting, blinds etc.
Control should be done on the exterior. Treatments around the foundation and lower windows and doors will usually stop them from coming in and reduce the population size. Because of their small size, it is difficult to seal them out. Inside, use the vacuum instead of wiping or brushing to try and avoid stains or smears.