Fungus gnats are small, dark, short-lived gnats, of the families Sciaridae, Diadocidiidae, Ditomyiidae, Keroplatidae, Bolitophilidae, and Mycetophilidae (order Diptera); they are sometimes placed in the superfamily Mycetophiloidea. The larvae feed on plant roots and fungi, helping in the decomposition of organic matter.
In each of these situations, you experienced the work of the three types of heat transfer: conduction, convection, and radiation. Conduction, or direct heat, occurs when the faster moving molecules of the fire collide with the cooler molecules of the marshmallow, causing them to move faster and become hot.
Heat transfer refers to the physical process by which heat energy moves from one area to another. The Heat Transfer Methods figure above illustrates various heat transfer methods. Branches above the fire are receiving heat by convection and radiation.