The Dixella indiana species group: morphological and molecular analyses of Dixella indiana (Dyar 1925), Dixa pseudindiana Peters 1981, and three cryptic species

Dixidae (Diptera: Culicoidea) is a medically insignificant family of lower fly closely related to Culicidae. Their lesser importance has contributed to a lack of study and, as a result, much information about Dixidae has yet to be elucidated. Dixella indiana (Dyar 1925) and Dixa pseudindiana Peters 1981 are both Nearctic members of Dixidae previously thought to belong to differing genera after decades since their descriptions. Thorough examination of structural characters, particularly male terminalia, and application of DNA fingerprinting, i.e., integrative taxonomy, has revealed these two species are actually closely related. As a result, Dixa pseudindiana Peters 1981 is hereby transferred to Dixella Dyar & Shannon, 1924. Additionally, three undescribed closely related species likely mistaken for Dixella indiana in past studies were revealed. Based on these data, the Dixella indiana species group is erected to include the aforementioned two species and three newly discovered ones designated here as D. indiana “Northern”, D. pseudindiana “Terrapin”, and D. indiana “LTRC”. The findings reported herein call into question the validity of most past records of Dixella indiana and Dixella pseudindiana, certainly those based upon larvae. Additionally, the group member’s distribution, ecology, and phylogenetic relationships are presented.