Dad planted a swamp milkweed seed in a flower pot and put the flower pot in a tub full of water. Soon, the swamp milkweed grew. Once it had gotten a little bit of size, I noticed a monarch caterpillar on the foliage.
I watched this caterpillar as it grew larger day by day. One day I looked for it, and did not see it at first. After looking closely I found what was left of it.
The insect that is sucking its life juices is the larval form of some type of true bug.
I have to admit that although I wanted to see the complete life cycle of the monarch, I thought the bug was neat looking too. Predators have their place. If not for predators, the world would be overrun with all manners of animals which might otherwise cause no problems.
Monarch adults and caterpillars are brightly colored, which is a signal to vertebrate predators that they are toxic and taste bad. They pick up these toxic chemicals from the milkweed plant. Evidently the chemicals are not so toxic to other insects.