Posted: 17/07/2014 at 10:43
Not sure if I have this quite right, but are we taking 'soil' or compost here?
I suspect it's compost, in which case they will be fungus gnats.
Fungus gnats” (scientific name Sciaridae).....these live in potted plant compost. They can be very hard to get rid of, depending on how many infested pots you've got.
Nearly everyone who has potted plants has these flies in their homes but they sometimes become a nuisance.
Re-pot the plant completely with sterilised potting compost and spay the compost with BTi (available as 'Gnatrol' in the garden centre)
If they are in garden soil, disregard the above.