I agree with the use of Insecticidal Soap; it's the go to in my gardening supplies!
I don't know what insect you have in the soil of your plant but for comparison there are side by side images of a springtail and a thrip here: http://images.plant-care.com/s...
~ I'm an old gal who still loves playing in the dirt!
~ Playing in the dirt is my therapy ... and I'm in therapy a lot!