Tree/leaf hopper ? Maybe Aphid??

Hi EVeryone , Glad this site will still be available . This is one of the best around and I have learned a great deal for my hungry mind.

Yesterday I noticed on the lower leaves of my Rudbeckia masses of insects on the underside.
The lower leaves were curled slightly as if they were wilting . This prompted me to look closer.
I have come upon aphids that were being milked by the small brown ant.

But these insects were being milked by the very large black ant. I want to add these insects do not appear to look like aphids . Rather they look like a tree/leaf hopper with the horned type back. The nymphs are very black in color and have clear wings . wing shape appeared to look exactly like lace bug .
The inscets all converged on the underside of leaf at the central vein only.
Any thoughts would be wonderful .

Another question I have is on this same plant I saw another creature. On the flower in the center was a worm/caterpillar. At first glance it looks like debri. It looked like shavings from the flowers center , but it was actullay a critter eating the center . The flower was in full bloom . I have never seen this type before and it was interesting. any ideas as to what it was ?
Any info would be great .
Laura