Today in my new, still incomplete garden, I found a whole gang or caterpillars having a ball on a pine tree. There were about 50 of them, yellow-beige with a dark brown line along their bodies and little spots above the bold line. They were eating verociously and left some transparent liquid where they munched (their saliva?)

I didn't want to kill them in case they were butterflies in the making. I took a pic with my cellphone but am not sure how to load it on this site.

I did some search on FL Gardenweb but could only find mention of green caterpillars and ferocious looking spikey ones but none like these. How do I tell if they are good or bad?