Milkweed is the sole host plant where female monarchs lay their eggs, usually placing a single egg on the underside of a leaf near the top of the plant. However, they also lay eggs on buds, on top of leaves, and new leaves near the top of the plant. As they lay eggs, females secrete a small amount of glue to attach the eggs securely to the plant. Over a 2-5 week period, each female typically lays 300-500 eggs in the wild.

Each egg, formed inside the female before fertilization, has a hard outer shell called the chorion, lined with a wax layer to prevent dehydration. Monarch eggs, about the size of a pinhead, are creamy white and football-shaped. Depending on the temperature, eggs hatch within 3-5 days. Just before hatching, the dark pigmentation of the larva’s head becomes visible through the translucent eggshell, giving the egg its characteristic black dot.