Question
I have bag worms in a row of evergreens (now sure exactly which kind) I've sprayed them with an insectacide.   My question is "how do I tell if it worked ?   How do I know if they're dead ?   do they fall off, or change color ??

         Thanks for your help,   Stan

Answer
The caterpillar lives in side the bag. You can cut open the bag and see if they are still alive. The bag will usually still hang on the twig even after the caterpillar inside is dead. Also you should see some moving around especially just at sun set. I would guess they are dead.