This Neotropical genus includes several species, with one of them widely distributed and weedy in tropical regions worldwide, particularly in open wastelands and disturbed areas on sandy or degraded soils. Mitracarpus is similar to Spermacoce in its herbaceous habit; distinctive interpetiolar stipules that are fused to the petioles or leaf bases on each side, rounded to truncate, and setose (i.e., with 3-11 bristles or linear segments); its small white flowers in sessile axillary and terminal groups; and its small capsular fruits. However Mitracarpus can be easily distinguished by its fruits, which are circumscissile (i.e., splitting around the equator so the top with the persistent calyx lobes falls off while the bottom remains attached to the plant), and its seeds, which are oblate (i.e., subglobose but kind of squashed) with a large impressed "X" or cruciate scar on one side. In contrast the fruits of Spermacoce open longitudinally, and the seeds are oblong with a single longitudinal furrow or scar. Also Mitracarpus can often be recognized in flower by its calyx lobes, which are almost as long as the corollas and have hyaline, usually somwhat irregular to erose margins.