Answer: The leaf loss is more likely due to moving the ficus into your home where the light, temperature and humidity is different than where it was growing before. After some adjustment period, the plant should leaf out again. Sometimes just the act of transporting plant in a vehicle can stress them. Just water when the soil dries out and keep the plant away from heat registers or air conditioning vents and it should recover.
As for the soil pests, I'm not sure from your description whether you are dealing with Millipedes or Centipedes - they are quite similar in appearance.
Millipedes can build up in potted plants. They feed on plant parts, but more frequently, on decaying organic material. They become a nuisance when present in large numbers. Many species can occur on plants. They vary in color and can be tiny or up to 11/2 inches or more in length. They are easily identified by the presence of many legs, by the rounded shape, and by their slow movement.
Centipedes are not plant pests. They feed on many insects and insect relatives and, thus, are beneficial. While they resemble millipedes by having many legs, they are very flat and very fast moving. They vary in size (1/4 to 2 inches) as well as in color. Some of the larger ones often bite when disturbed. So, if their presence is annoying, remove them carefully and place them outdoors where they can continue to be useful in nature's scheme of things.
If there are great numbers of these critters, your best option is to repot the plant in fresh potting soil and toss the old potting soil into a garden bed.
Best wishes with your ficus!
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