Calolydella

Abstract: Background Twenty-three new species of the genus Calolydella Townsend, 1927 (Diptera: Tachinidae) are described, all reared from multiple species of wild-caught caterpillars across a wide variety of families (Lepidoptera: Crambidae; Erebidae; Geometridae; Hesperiidae; Lycaenidae; Nymphalidae; Pieridae; Riodinidae; and Sphingidae) All caterpillars were collected within Area de Conservacion Guanacaste (ACG), in northwestern Costa Rica This study provides a concise description of each new species using morphology, life history, molecular data, and photographic documentation In addition to the new species, we also provide a generic redescription and revised key to species of the genus Calolydella from Central and South America New information The following 23 new species of Calolydella are described by Fleming and Wood: C adelinamoralesaesp n, C alexanderjamesisp n, C argenteasp n, C aureofaciessp n, C bicolorsp n, C bifissussp n, C crocatasp n, C destitutasp n, C discalissp n, C erasmocoronadoisp n, C felipechavarriaisp n, C fredriksjobergisp n, C inflatipalpissp n, C interruptasp n, C nigripalpissp n, C omissasp n, C ordinalissp n, C renemalaiseisp n, C susanaroibasaesp n, C tanyadapkeyaesp n, C tenebrosasp n, C timjamesisp n, C virginiajamesaesp nLydella frugale Curran, 1934 is proposed as a new synonym of Pygophorinia peruviana Townsend, 1927, syn n, under the combination Calolydella frugale (Curran, 1934), comb n