Determine which butterfly species will be shown in the food web. Using reliable sources of information, list the major plants eaten as leaves by the caterpillar form and as flower nectar by the adult butterfly. Specialist butterflies will use a small number of specific plants, while generalist butterflies may use many.
List the major predators of the caterpillar and adult butterfly forms, again using reliable information sources.
Write the butterfly species name in the center of a piece of paper. Draw an arrow pointing to a plant eaten by the butterfly or caterpillar. Repeat with all the major plants, so that each arrow points to a plant eaten. Some diagrams put all plant species below the animals, to represent the primary producers – those that create their own food source from sunlight and nutrients.
Write the names of major predators – those that eat the butterfly – around the upper perimeter of the diagram. For each predator, place an arrow that points from its name to the butterfly in the center.
Place additional arrows from predators to other species consumed. Birds may eat other insect predators or plants, bypassing the focal butterfly species. These additional relationships demonstrate the complexity of a food web compared to a simpler food chain diagram.