What are the little brown balls in the pot?
Those little balls are 'frass' or caterpillar poo! It means the caterpillars are eating and growing!
Why are the caterpillars spinning silky webbing?
It is a good sign if there is webbing in the caterpillar pot. The webbing protects the caterpillars from many dangers. Caterpillars use the webbing to stick to their host plants, as the wind could easily blow them off leaves. Their true front legs have hooks which they use to walk on the silk like a ladder.