Trophic shifts are powerful drivers of animal diversification. The transition into carnivory is a profound dietary shift that has evolved numerous times in animals, but underlying mechanisms for this transition are poorly understood. Lineages that have recently adopted predatory lifestyles are thus compelling models for understanding the proximate and ultimate causes behind animal carnivory. Within the phylum Annelida, ancient origins of carnivory have led to highly successful groups like leeches, while recent acquisitions of carnivory have also occurred. Chaetogaster, a genus of predatory, asexual freshwater oligochaetes is one widespread example, making it an outstanding model to study the integrative biology of this transition. We present a new molecular phylogeny of the genus, using COI and ITS2 from 264 specimens collected across Europe and North America, plus an 18S metabarcoding gut-content analysis on a subset of specimens. Our phylogeny identifies 16 putative new species, suggesting wide-scale cryptic diversity, and reveals surprising relationships between the known parasitic, predatory, and omnivorous representatives. The gut-content analysis is in progress, with the goal of identifying prey DNA in the guts of worms and mapping dietary transitions onto the tree. Combining our phylogenetic and gut content data, we will test several scenarios of trophic evolution that link the diets of basal, potentially non-predatory Chaetogasters to the highly predatory condition of more derived Chaetogaster species. This study will illuminate possible transitions that led to other diverse carnivorous lineages, such as leeches, and it will improve our understanding of trophic evolution in animals.