Monitoring Results
Interactions with Milkweed
The larvae can then eat without encountering much latex beyond their hole.
1st instar monarch feeding pattern
Larger larvae chew a notch (see picture) through the base of the leaf midvein, thus preventing latex flow to the entire plant. However, many larvae still succumb to this source of mortality; Zalucki and Brower (1992) found that almost 30% of first instar larvae feeding on the sandhill milkweed plant in Florida were killed by milkweed latex.
5th instar feeding on "notched" milkweed leaf
Milkweed plants contain a sticky latex that can glue a monarch's mandibles shut or even mire its entire body in a sticky trap (e.g. Zalucki and Brower 1992). Monarch eating patterns often reflect the care they take to avoid this plant defense. The latex flows through the veins in the leaves, and young larvae chew a characteristic moon-shaped trench in the leave that prevents latex from flowing to the area beyond it.
References