Could be white fly. We need to see a picture of them, really, or a description of what they look like. Are they flies, worms, beetles? Whatever they are, just give them a good squish with water from your hose, a couple of times a week and that usually does the trick. Don't use too much insecticide near food that's going to be eaten. Annie Cumbria)

Also planting marigolds close to toms helps, whitefly don`t like them, I always plant a few in my greenhouses...

Whitefly don't like to stay on the soil, but live on the leaves, though you may get some dead ones down below if the infestation is severe. If they aren't moving, they may also be the discarded skins of growing greenfly or blackfly on the foliage above. If they are moving around, they are most likely to be springtails or tiny centipedes or millipedes, neutral to beneficial in action.

there called council workers i believe . quit a rare breed now but they do come out once every so often lol .

True, but those usually have brilliant orange or acid yellow backs, don't they?! : D

lol x