The naturalist in Nicaragua: A narrative of a residence at the gold mines of Chontales; journeys in the savannahs and forests, with observations on animals and plants in reference to the theory of evolution of living forms.

In this book Belt 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" (Wikipedia article on Thomas Belt, accessed 07-31-2016).

Digital facsimile from the Biodiversity Heritage Library at this link.