JanFeb96 More Monarch Magic Several times in the past, we have discussed the monarch butterfly as an example of the incredible design that has been built into living things. The migratory pattern of monarchs is an incredible thing to study as they travel thousands of miles from their summering areas to their wintering areas in Mexico or in central California. The mechanisms of flight which allow them to take advantage of wind is another area of study that is fascinating. How these butterflies know to fly high in the air when the wind is behind them and close to the ground when the wind is against them, giving them optimum use of wind currents, is a mystery. A new discovery has added to our appreciation of this incredible creature.
Monarchs have a built-in protective device to avoid being eaten.
The protective device is a noxious chemical that accumulates in their body due to their diet. The main food of he monarch caterpillar is milkweed which contains cardenolide, a toxin that tastes bad and prevents animals from eating the monarch. When the monarch migrates, there is no milkweed on their migratory journey and thus no cardenolide. The monarch avoids becoming a food for animals by sipping the nectar of a variety of plants which contain pyrrolizidine alkaloids. This material is also toxic and simply picks up where the cardenolides leave off.