Help me identify this pest

This one I've never seen before... I found several bugs on my coriander. I can't post a picture since they're too small, about the size of a short grain of rice. They are covered in what looks like white spikes of cotton wool and they move quite fast (like a bug with legs, not like a caterpillar). If touched, the "cotton spikes" fall off. Any idea what they are???

Thanks for the suggestion, but it's not the one I have. The ones on my plant don't have wings, and they have "tufts" of white fluff rather than being like the ones in the picture. They look quite peculiar...

I've found out what they are, and I feel like a total idiot. They were larvae of an insect nicknamed "mealybug destroyer".
http://www.biosurvey.ou.edu/okwild/misc/mbdest.html
Of course I only identified it after I uprooted the coriander and put everything in the compost heap: these are really helpful insects, and people pay good money for them.
I hope the poor * survive the trip to the compost heap... Next time I should avoid the "kill first, then ask question". But they looked so weird that I freaked out...

How cute,  they've got dread locks