Hi Rozy,
The woes of
plant-sitting! Evidently, those
plants have springtails. They will not harm the
plants, but they can easily spread to other
plants. They are also often a symptom of soil that has been kept too moist.
Springtails feed on decaying organic matter found in potting mixes that are kept moist. Try to keep the soil as dry as possible. Remove all loose soil from the surface and put a light layer of sand or diatomaceous earth on the soil surface. These substances have sharp edges that carve up the critters. Another safe technique is to place ½ inch slices of raw
potato on the surface of the soil. Every day or so, discard the slices along with the springtails. Repeat this until there are no more pests on the
potato.
Prevention is often the best remedy. Use sterile potting mixes that are free of pine bark. The potting mix should have ample drainage material, such as perlite so that it drains well and allows the soil to dry out frequently. Springtails can nearly always be traced back to overwatering and/or poor soil quality.
Good luck!
