New garden pests

Hi Gerry,Darren here again. I emailed you recently regarding bulbs.I have another question if you could answer and possibly include in the magazine? However, Id like a a reply before waiting next issue or my plants will be gone :-)I’m 25 and have been gardening for over 13 years. This year is my first year to encounter such strange, if not new, garden flies. They are similar to green fly but very black/darky purple and have taken a liking to my nasturshams and Canary Creeper in particular. I have tried spraying them with insecticide but they still appear unchanged once dry.While I am familar with black fly, these seem to be different and only attracted to the above two plants. They tend to gather in circled groups too on the under base of the nastursham leaves. And if I squeeze them, I get a redish blood like stain on my hands. Can you help as they are eating my plants… I attached photo..ThanksDarren