The type species of Costarina, C. plena (O. P.-Cambridge), is widely distributed, occurring from southern Mexico to southern Costa Rica, but Costa Rica also houses an extraordinarily large fauna of endemic, less widely distributed Costarina species. In addition to the two previously described species, C. meridina (Chickering, the female of which is newly described) and C. watina (Chickering), 49 new endemic species are described: C. paraplena, superplena, maritza, cima, elena, monte, murphyorum, chiles, upala, poas, selva, viejo, rafael, azul, carara, nara, aguirre, quepos, carrillo, ramon, isidro, san, cuerici, leones, junio, reventazon, macho, cruz, chonta, barbilla, espavel, veragua, pity, penshurst, hitoy, mooreorum, cerere, frantzius, gemelo, pittier, alturas, cruces, ubicki, palmar, parabio, semibio, jimenez, parapalmar, and osa. Two other species also occur in Costa Rica. Costarina concinna (Chickering) is placed as the male (and hence a senior synonym) of C. potena (Chickering), both of which were described from Volcán, Panama; the species appears to be a relatively widespread, southern vicariant of C. plena. The Panamanian species C. obtina (Chickering) is also newly recorded from Costa Rica, and its female is described for the first time.