Insects can live in house plant soil. The most common of these is the fungus gnat. The adult lays eggs that produce small white maggots. The maggots eat fungi growing on the organic matter in the soil but they can feed on the roots. The insect is most likely to be a problem when the soil is kept too moist. The maggots can be seen wriggling on the soil surface when the plant is watered.
A malathion drench will control the insects but the pesticide may be more harmful to the plant than the insects.