Although associated with the Great Plains, bison were in Ohio when European settlers arrived. From E. N. Transeau we know that Ohio's prairies were once connected with prairies to the west, and it makes sense that if prairie plants are here, prairie animals should also be here. Although the bison are gone, many other species of animals associated with prairies are in Ohio - and they are still associated with prairies. Part of the assessment of the health of an ecosystem includes a measurement of all the plants and animals in the system. Prairies, wetlands, and other habitats are indicated visually by plants, yet the complete ecosystem includes all the plants and animals.
Ducks help indicate a wetland, and meadow larks help indicate a grassland.
Animals that are much smaller in size, insects, are also excellent indicators of each of these, and other, habitats. Insects account for more than one half the species of all living organisms on Earth. Their diversity, abundance, small size, and the specialized nature of their requirements mean that they are important components of our biological diversity, and they are excellent indicators of the health of our environment. Lepidoptera, butterflies and moths, are ideal ambassadors of the insect world for measuring biological diversity, and for making assessments of the health of specialized habitats. Their abundance means there are many species to measure.