This is a very tiny lady beetle, usually less than 2 mm, sometimes up to 3 mm. It is unusual in being a fungus and mildew feeder. Indeed, though you can't tell here, the leaf it is on had quite a bit of mildew and nearby were other leaves more mildewed, and with more of these little insects. In my own garden, I have found a large number of these lady beetles in all stages, larva, nymph, and adult, on mildewed leaves of sunflowers. At first glance they look like very tiny versions of the fourteen-spotted lady beetle.