My first thought is that they might be aphids or spider mites. Aphids can be easily seen, whereas spider mites are microscopic and only seen if you shake the plant over a piece of paper and see the flecks crawling. Both insects suck the plant juices and can cause distortion. The infestation would need to be pretty bad for them to kill the plant. It's possible that it's entirely some other insect. Using a strong stream of water from a garden hose will knock most of them of them off. You should cut off any of the plant that has turned black. Once they're done flowering they need to be cut back anyway to the basal foliage. If you have photos, send them to the email on this response or consider taking a sample to a local garden center for positive identification.