MILKWEEDS.
Most of us like milkweeds. They are not so troublesome as the dandelions and thistles. They generally grow in waste places, along stone walls, or outside fences, where they do no harm to the crops but make the roadsides charming. Most kinds of milkweeds have a milky juice, as their name tells. It is thicker and stickier than the dandelion juice, and is very disagreeable if one gets it on his fingers.
This, no doubt, is why the plant makes it that way. It does not wish us to get its juice on our fingers; it wishes us to let it alone. It also wishes animals to let it alone and not eat it; and most animals are not fond of it. This is not true, however, of certain caterpillars.
Towards fall you will generally see the milkweed leaves covered with bright yellow and black caterpillars that certainly are lovely whether you think, so or not.
If you take the largest of these caterpillars and put them in a box of earth with plenty of fresh milkweed leaves to eat as long as they want to eat (which will not be long), you will see what happens.