Many butterflies adore the sweet taste of sap dripping from trees. The sap is actually the fluid transported in the cells within in the tree. The xylem and phloem are responsible for carrying water, sugar, hormones, minerals, and nutrients to different parts of the tree. Many times carbon dioxide can build up inside the tree or heat pressure in the tree can force the sap through cracks or openings. The next time you are walking in a wooded area, look closely at the tree bark; you may be pleasantly surprised to find your favorite butterfly having a sweet treat.