Newt
Newts, as with salamanders in general and other amphibians, serve as bioindicators because of their thin, sensitive skin and evidence of their presence (or absence) can serve as an indicator of the health of the environment. Most species are highly sensitive to subtle changes in the pH level of the streams and lakes where they live. Because their skin is permeable to water, they absorb oxygen and other substances they need through their skin. Scientists study the stability of the amphibian population when studying the water quality of a particular body of water.
Thomas Belt
In this book, he also first described the mutualistic relationship of certain Acacias and the ant we now know as "Pseudomyrmex spinicola". These are a species of red myrmecophyte-inhabiting neotropical ants which are found only in Nicaragua and Costa Rica. They live in the thorns of a tropical tree, "Acacia collinsii", feeding on nectaries along with the protein and lipid-rich pods produced by the plant for the ants and now known as Belsian bodies (or Beltian bodies) in honor of Belt.