I was out in my backyard today. I was pulling up weeds growing in the backyard. Then I noticed these bugs all over them. I’ve pulled them up before and never saw these bugs. I’m a garden noob in the biggest sense. So I want to try and figure out what they are before I disturb the plant and they run, jump or fly everywhere. What are they? Are they harmful? I’m located in Ontario, Waterdown/Hamilton to be more precise.
They appear to be ants tending a colony of white aphids on a thistle plant. You definitely don't want them to spread to any desirable plants. It would be best to quickly pull up the weed, toss it into a container with a lid, and dispose of the whole lot far from the yard.