I've spent 3 hours trawling the depths of Google Images and entomology sites to try and identify these beetles, but to no avail. Can anyone help me decide whether I need to go all homicidal on these critters? I'm in the South East corner of Australia if that helps. They look the same apart from the different colouring and the dark ones seem to like mounting the green ones, so an uneducated guess tells me the green are female.
There seems to be a hell of a lot of them and I've only spotted them on my annums so far, which are in a garden bed only metres from the rest of my plants. The plants don't seem to be under stress and there is very little evidence of leaves being eaten, so I don't want to kill them if they're not doing any harm. I have not seen a single aphid on any of my plants so it's possible these beetles are the reason why. Any advice will be greatly appreciated.
Thanks.
There seems to be a hell of a lot of them and I've only spotted them on my annums so far, which are in a garden bed only metres from the rest of my plants. The plants don't seem to be under stress and there is very little evidence of leaves being eaten, so I don't want to kill them if they're not doing any harm. I have not seen a single aphid on any of my plants so it's possible these beetles are the reason why. Any advice will be greatly appreciated.
Thanks.
I agree with mel, they look like stink bugs. Sounds a bit morbid, but crush some up and spray or place them around your plants, the smell that they make when squashed warns the others off. And its kinda fun..... 
That's a shot of a few that were residing on my Datil plant last year. They never bothered the plant.
