hard to say, they usually settle on one plant, once you find them simply spray them with soapy water (may not be enough though) or just pick them off.

I don't wan tto scare but for about 6months we had what I thought were fruit flies but they were adult woodworm beetles.

so try and catch one and have a close look. the head shape looks like they are wearing a crash hat !

How do you know they are not fruit/fungus flies? From your description it sounds like them. Had loads of those in the past when I've kept indoor plants. They love wet/damp soil in which eggs are laid. There is special horticultural sticky tabs you can buy and locate them above the plant soil which will catch them by the score. Squashing a few isn't going to make much difference.You have to break their life cycle.

They sound like a very common problem that almost all of us get, especially if you put an indoor plant out during the summer or brought one in to overwinter. They are called Fungus gnats. Tiny black flies. You can spray them with household fly spray. As Timmyh has said, covering with a layer of grist does help.

Thank you al for your advice. Will try grit but also those sticky tabs. Glad to hear that I'm no alone in being pestered by them.

Letting the plant dry out between watering helps somewhat but realistically an insecticide is best.

If you can get a product containing Bacillus thuringiensis israelensis, that will kill the larvae of fungus gnats without harming plants, pets, or people. Pouring chlorine bleach down the drains may also help, since they have been known to colonize the plumbing, too.

I get them often,especially when having had the plants outside in summer,so I agree with Botanic.. yellow sticky traps work well for mine..It's amazing how many you can see,when they are on a bright colour..I now put them in a few of the pots of overwintering plants and cuttings,as soon as I bring them indoors ..no more TV watching with us,or seeing what we are having for dinner :o) Cost approx £4 from Garden Centres..for a 24 pack..Each is said to last for about 3 months..