Try spritzing them with a mild solution of water and dishsoap. I don't know what kind of insects you have, but that works on a variety of pests and won't hurt your seedlings.

Small lurking flies are fungus gnats. They don't touch the seedlings, they eat fungus (duh!), but their larvae live in the soil eating anything organic. One munch through the root of a seedling and it is dead.

The first control is always prevention. Fungus gnats like moist organic soil (peat!) which supports the fungus that they eat. Allow the surface of the soil to dry out, cover it with a thin layer of coarse sand or grit, and try to kill the gnats themselves with a sticky trap or a contact insecticide on the pots or pebble trays.

I had some and I ordered gnatrol online. It's actually the same natural bacteria that's in mosquito dunks (BT-don't ask me what it stands for :) ) anyway those bacteria kill the larvae. Worked like a charm for me. I found out after that I could've used water with the mosquito dunks soaked in it overnight to get the same results. Much cheaper than gnatrol.