text: my butterfly bush had small green fly larva living in the stems. any idea what they are and how to stop them? the butterfly bush was the black knight variety.  once i found the larva and an adult fly emerging from the stem i broke off, i dug up the plant and thew it away. if you are in the usa.  i recommend that you call your local county cooperative extension service office.  they can help you identify your pest.  here are two websites with many excellent images.  i don't know much about insects, but i was researching sawflies earlier this year, and i believe some of them pupate inside of stems.  whatever it is, i would first try to find out what it is.  it may have an important role elsewhere in your garden.  when you discover what it is, if you decide to control it, please do so with a soap spray.  chances are birds are visiting your garden, and you wouldn't want them feeding on toxic insects.  also, many products on the market are hazardous to your health, and stay in the environment for a long time.  if you are observant, you learn much important and interesting information about insects.  examine nearby plants,  does it feed on other plants, or is it selective.  what time of year does it appear and disappear. where is it on the plant?  on the leaves, stems, etc.  good luck, and enjoy your garden.  black knight is one of my favorite buddelias.