The genus Brenthia, with 85 described species, is the second largest genus of metalmark moths (Choreutidae), a relatively small apoditrysian family. Although members of this genus occur in all biogeographic regions, their highest diversity is in tropical areas. This genus, as well as the rest of the family, is poorly known: many species are still undescribed, life history information exists for only a few of them, and their phylogenetic relationships are uncertain. My ultrastructural studies of larval morphology suggest a close relationship of choreutids and tortricids. Preliminary results of a molecular phylogenetic analysis are presented and adult and immature morphology, including the ultrastructure of larvae and pupae, is illustrated. Both larvae and pupae have unusually long hairs. Of specific significance are the extremely long SD1 setae on A9, which so far as known not only represent a synapomorphy for the genus, but perhaps represent the relatively longest setae known for the order. Experimental studies suggest that these setae perform an important function for the larva—in conjunction with the wispy webbing that the larva spins they seem to be functioning as a monitoring system used in detection of disturbances.