Passion flower butterflies, also known as Heliconius butterflies, live in the canopy layer of the rainforest. This is the uppermost layer, where the trees are the tallest and receive the most sunlight.

Here's why:

* Food source: Passion flower butterflies rely on passion flowers for food (both nectar and leaves for their caterpillars). Passion flowers are often found in the canopy, making this layer their primary habitat.

* Sunlight: The canopy is the sunniest part of the rainforest, which is important for the butterflies' metabolism and flight.

* Protection: While the canopy is exposed to the elements, it also offers some protection from predators and harsh weather conditions.

Let me know if you have any other questions!