A balance between Man and Nature

Took a walk on the wild side - of the garden, that is - to see how the lemon tree is doing. I recently sprayed it with an eco-friendly spray to get rid of the aphid/whitefly population that was infesting it in droves. I couldn't reach the highest parts without giving myself an intensive treatment too (although at least I know I won't get aphids on my face) and so there are still areas which are infested. A golden orb spider has set up web and home between the lemon tree and the honeysuckle, rather inconveniently blocking easy access to the actual lemons when I want to pick them. I don't want to sever any of the web links (sounds a bit technical, doesn't it?) so have to ease my arm through the branches, running the gauntlet of the vicious thorns this particular variety of lemon tree bears.
As I peered short-sightedly through the gnarled branches, I spotted a large brown ball slightly larger than a cricket ball and immediately thought it might be the fungus that killed off most of the Port Jackson trees some years back. I reached out and poked it with my finger, and it immediately dissolved into a seething mass of ants! It was an ant nest, the ants being a little larger than the Argentinian species, and in no time they were swarming up my finger and biting in self-defence against this most unwelcome intrusion! I beat a hasty retreat and left them to regroup and settle back into domestic bliss and went to fetch the camera.
I had to poke my head through the spider web to get this rather poor shot, but there was no other way to get near it. The pic with the leaf shows the food that they are living on which has obviously attracted them to make their nest in a tree (I wonder if this is normal ant behaviour - any ant specialists out there?) and so am relieved that no poison was used. I won't be spraying again, as this will destroy this little ecosystem out there in the wilds of the back garden. After all, isn't that what we are trying to achieve - a balance between man and nature?