A recently-brought plant infected my other two houseplants with white, head-lice-looking creatures that jump. The soil was swarming with different sizes of these after only a couple of days. The biggest was probably 1-2mm. After some research, I've diagnosed these as springtails. I live in a warm, dry new-build apartment (no access to a garden), so am fairly certain it was my new plant which brought them into my house. I've since been trying to kill them unsuccessfully using a standard insecticide, which took care of most of the population straight away. However, if I leave it a couple of days between applications, I start seeing a couple of big springtails foraging again in the soil in my different plants. I don't see the babies any more and assume the insecticide took care of those but how are the big ones still alive? If I'm fast enough to get them directly with the spray, it does seem to kill them, but why is treating the plant's soil every few days not getting rid of any I don't manage to hit directly? Is there anything else anyone can suggest?