Just before someone gets nervous do they experience cocoons in their stomachs?

After some thought, its obvious. The answer must be yes. The cycle is well known after all: first comes the egg, then the caterpillar, then the cocoon (or scientifically: chrysalis), then the butterfly. You can't have butterflies without the previous three chains in the life cycle.
The prevailing thought must conclusively be that people accidentally eat the eggs. Next, the caterpillars are born and that is when you can experience the having-creepy-crawling-things-in-your-stomach feeling, because you do in fact have crawling things in your stomach. After the caterpillars have munched enough on your enjoyed salad lunch, they cocoon themselves. However since cocoons do not do much, you do not notice them hanging around in your stomach. You only get to relish the whole experience when the butterflies emerge!

But, how do they manage to time this cycle perfectly with when you get nervous?