Wow, I had no idea they will eat pumpkin chunks. I assume this is the meat of the pumpkin, not the leaves? Don't suppose it provides them with any of the cardio-glycosides though.

"Don't suppose it provides them with any of the cardio-glycosides though."

Doubtful, although pumpkin has been known to induce coma in humans when served with whipped cream after a large meal.

All kidding aside, they probably will be protected to some degree if they have eaten milkweed up to this point. Monarchs experience a wide variation in the amount of cardenolides in the plants they consume. Depending on the species, the quality of the soil, the location of herbivory, and the time of year, the levels can be different. Monarchs may have really high levels or none at all. It is really complex and they are still studying it.

Below, I have linked a study discussing what happens when the nitrogen levels are different in milkweed plants. Very interesting stuff!

Elisabeth

Here is a link that might be useful: Milkweed, Monarchs, and Nitrogen