I have seen 1/2" or smaller brown worm like insect in the soil of my...
They are probably fungus gnat larvae. Do you see little flies flying around your indoor plants? If so, those may be the adult stage of that same worm in your potting soil. The only control for them is to let the potting media dry out between waterings. Fungus gnats love moist soil and can only reproduce in moist soil. You may be overwatering your plants a little.
Here is a link to a UK publication on houseplant pests: http://www2.ca.uky.edu/entomology/entfacts/ef406.asp
There are no gnats or anything flying around. They are little and have lots of legs and are brown. The look hard but when I caught one it smashed easily.
The best thing is to bring the insect in to your Extension office and they can get it positively identified. It is very difficult to ID something with just a written description sometimes. If you feel I'm in error, that's the next step.