I have adopted an indoor spider plant in a fairly large terra cotta planter that has quite a few hanging baby plants and I have noticed many black droppings around it in the past few days. I have looked all over for what I would think would be a caterpillar or something that would leave droppings. The droppings are hard, black and pellet shaped, about the size of a millet grain. There are some brown markings on the leaves, not a lot of evidence of chewing, just an occasional hole here and there. I can't seem to figure out what is leaving these droppings. Thank you!