Hi Lara, it sounds like aphids or leaf hoppers, but if not then I don't know what they would be.

Here's a great photographic reference that I use. The photos are really helpful for working out where to begin.

http://www.gardenersworld.com/how-to...ory/veg-herbs/


And here are some more I found while searching for you:

http://forums.gardenweb.com/forums/l...200492528.html

http://forums.gardenweb.com/forums/l...033321510.html

Before you can work out what to do about your pests, you'll first have to identify them. Once you've done that we can help you look for a remedy. I sort of hope they're aphids because they're relatively easy to control.

I hope that helps some.