Red mites are small arthropods, the body length of adults ranges from about 0.6 to 0.8 mm, while specimens saturated with blood can enlarge the body size by 30%, reaching a length of about 1 mm.
Nymphs and adults have four pairs of legs, while the non-blood-drawing, inactive larvae are six-legged. At the edges of the ventral side of the body there are spiracles (peritremae) functioning as organs of gas exchange and regulation of the hydration level of the mite’s body.
The color of the body surface depends on food saturation. Hungry specimens are whitish or grayish, while mites turn bright red or ruby red after blood collection.