Revision of the Mesoamerican species of Townsend (Diptera: Tachinidae) and description of twenty-three new species reared from caterpillars in Area de Conservación Guanacaste, northwestern Costa Rica.

Background: Twenty-three new species of the genus 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 Conservación 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 from Central and South America.

New Information: The following 23 new species of are described by Fleming and Wood: , , , , , , , , , , , , , , , , , , , , , , Curran, 1934 is proposed as a new synonym of Townsend, 1927, , under the combination (Curran, 1934),