This paper examines the group of arboreal
anurans known as tree frogs, which possess the characteristic, expanded, terminal
digital pads that assist in adhesion to the steep surfaces present in their natural environment. It looks at how the unique morphology and physical
mechanisms of these structures have been studied for over a century and how it is only recently with the advances in transmission and scanning electron microscopy that it has become possible to study the pads in detail. It discusses how, even with this new insight into the ultrastructure of the pads, debate continues among zoologists over the nature and roles played by the various adhesive mechanisms of the toe pad and how the distribution of
digital pads over five families suggests that the feature evolved independently many times in an interesting example of convergent evolution.