Where do monarch caterpillars feed?

The majority of monarch eggs are laid on the underside of milkweed leaves on the upper portion of the plant, and this is where young caterpillars tend to feed. The upper portion of milkweed plants also has been found to most likely have the lowest pollen levels because the leaves often point up. Researchers found that upper leaves had only 30 to 50 percent of the pollen density found on leaves in the middle portion (Pleasants et al., 2001).

Similarly, young caterpillars do not tend to eat on the leaf midrib, where pollen densities were found to be higher.