I have spent an inordinate amount of time studying Loxandrine carabid beetles. This group has about 240 described species, all but a couple dozen from the Western Hemisphere. The bulk of the species diversity is in South America where we find nearly 200 species, but by my estimate, this is less than half of the true number. When full described they should top 500 species. A respectably large clade of beetles, if not crazy mega-diverse.
One persistent mystery is the distribution of color patterns in the group. Among the South and Central American species (and a few in North America) patterns of pale spots and vittae on the elytra are very common. Typically markings are humeral (near the “shoulder” of the elytra), along the parasutural interval (the first interval in the middle of the elytra) or apical (either as a central spot or along the lateral margin). The markings can be variously shaped and are red or yellow. These sorts of marks and their positions are seen across just about all carabid tribes. So common that one must seriously consider the possibility of a good adaptive reason. Perhaps they are aposomatic (warning would-be predators of the defensive chemicals they have) or the pattern is disruptive, enabling their escape from visual predators by breaking up the beetle-shaped outline.
Just jump over to Australia and things look quite different. The diversity is smaller, all the species of loxandrines of Australia, New Guinea and New Caledonia will only amount to about 100 species and most strikingly, not a single spot on any species except for one rather poorly marked, undescribed Cerabilia. Other carabids in Australia seem spotty enough. For example there are beautifully marked Leconomerus (Harpalini) and Abacetus (Abacetini). The one Cerabilia with it subtle vittae is found with a similarly marked Leconomerus, so perhaps mimicry is involved.
There is a question raised for me. What is it about the evolution and environment that these sister clades (Australian and New World taxa are reciprocally monophyletic) experienced that led to the spotty and spotless species we see now?