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The crescents form a complex group of poorly understood species, partly as a result of the fact that they are often very similar in appearance. Extensive genetic research by Wahlberg et al. (2003) has not clarified the species relationships. The northern and Pearl Crescent (P. tharos) can be difficult to tell apart, and these were treated as the same species in most of the older literature. Male Northern Crescents have a more solid orange upperside, while tharos has more extensive upperside black markings (the black line through the forewing median is continuous, not broken).The hindwing margin is mostly solid black in cocyta, but has a line of pale yellow crescents in tharos. The Tawny Crescent (P. batesii) has more upperside black markings than cocyta so is similar to tharos in this respect, but the tip of the antennal club is black and white, not not black, white and orange. This character is not reliable for separating females of these species. Female crescents in general have more black markings on the upperside and paler orange spots in addition to the orange ground colour; and are best identified by association with males from the same population.