Sorry, they come from the sky. The caterpillars are larva of a moth that the mom laid eggs on your buds. When it hatch out, it will munch on your buds and poop. The poop feed the mold and cause the rot to spread. Then the caterpillar turns into moth and fly away leaving behind a pile of shit that keeps on feeding the mold and the rot keep spreading. To kill them close to harvest time like this, I’ll only use organic caterpillar killer. But first you have to pick the rotted buds out. Gently pull away the rotted part (some would fall off by itself) to expose the stem then cut that stem off. You might be able to same the unrotten buds left. Then spray with hydrogen peroxide diluted half strength with water. When you harvest the buds, do the peroxide wash to sterilize it. You do NOT want to get those mold into your body.
@Joebuddin I just had to deal with it. See my post Help, buds rot! to get the links @Myfriendis410 gave me to get those cat-killer spray
These nasty critters do a lot of damage! I had to chop my cola off and threw away over a pound of green buds!
