Hi there!

So, on one of my saves, I've caught all the bugs but two: the golden dragonfly and the black dragonfly. I read the bug collection guide, and it says the black dragonfly appears when you have Venomous plants out. I have put out plenty of Venomous plants, and the Black Dragonfly hasn't appeared at all. Are there certain foliages you need to use? Because when I tried on a second save, the Black Dragonfly was the first bug I caught. And there weren't any Venomous plants out at all. What should I do?