Systematics, natural history, and evolution of the saw-lipped rove beetles (euaesthetinae): Progress and prospects for future research

The rove beetle subfamily Euaesthetinae is reviewed and information on the systematics, ecology, and evolution presented. Key morphological features of adults and larvae are discussed, and the current state of morphology-based phylogenetics and paleontological research is reviewed. Natural history information is compiled for most genera, and general ecological trends are highlighted. Euaesthetinae are probably monophyletic but with a suprageneric taxonomic structure likely poorly reflected by the current classification. They are nearly globally distributed in most habitats, and collection data suggests that their ecological diversity is not yet fully known or confirmed. The southern hemisphere and high-elevation faunas globally comprise mostly flightless species restricted to ground litter of diverse habitats. A division into groups extending from the general ground litter into either soil (endogenous) or aboveground habitats (mediated by highmoisture microhabitats, typically dense bryophyte growths) is suggested. Although Euaesthetinae are generally found in mesic habitats, a group of seemingly periaquatic taxa are primarily found in Holarctic riparian and wetland sites. Probable surface runners and arboreal (foliage-dwelling) species form two other (overlapping) ecological groupings, and the occurrence of some species in vertebrate and ant nests requires further investigation. Biological inferences are drawn from several different morphological features of the group suggesting diverse life histories for these tiny beetles. Updated fossil information is provided, and this indicates needed taxonomic changes and suggests a greater extinct taxonomic diversity than previously known. The fossil record and ecology of the group suggest that euaesthetine lineages are resistant to extinction over geological time making these beetles well-suited to historical biogeographic studies