Revision of Xanthomicrogaster Cameron, 1911 (Hymenoptera: Braconidae: Microgastrinae)

Subfamily Microgastrinae (Hymenoptera: Braconidae) is one of the largest subfamilies of parasitoid wasps, both in terms of number of described species as well as estimated total number of species. Containing ~57 genera and exclusively attacking Lepidoptera, most of the diversity is concentrated within a few very large genera, with many smaller genera, including Xanthomicrogaster Cameron, 1911, existing with unknown morphological boundaries, life histories, and habitat use information. Containing only four described species, Xanthomicrogaster is one of the smallest genera, with extremely little information known. In addition to this lack of knowledge, Xanthomicrogaster is an extremely rarely collected genus, both in Malaise traps and rearing projects. Through the large scale efforts of the Área de Conservación Guanacaste (ACG) project in Costa Rica, over 50 specimens of Xanthomicrogaster have been collected, both through Malaise traps and caterpillar rearing. In addition to these specimens, borrowed material of undescribed Xanthomicrogaster species from the Canadian National Collection (CNC) and Texas A&M University insect collection (TAMU) is examined in order to understand the variation and geographic range of the genus. Previous descriptions of the genus and the recognized species are examined and placed into context using the material from across the geographic range. Seven species are newly described here from the ACG project, identified using morphology, DNA sequences (COI, wingless, and 28S rDNA), and host caterpillar with host plant records. The morphological boundaries of the genus are proposed, and a dichotomous key to world species is presented to facilitate identification and future description of species. Two molecular phylogenies are produced, using appropriate outgroups: one for all newly described species using three genes, and one for all Xanthomicrogaster specimens obtained from the ACG project using the COI barcode region. Host caterpillar use with host plant records is examined in the context of the phylogeny, revealing that Xanthomicrogaster specialize on concealed hosts, especially within superfamily Gelechioidea (Lepidoptera). In addition, sexual dimorphism is examined for the first time, as associations could be made using COI barcode information, revealing that males are often darker than females and are never collected in Malaise traps. Color patterns in Xanthomicrogaster are examined, especially as they vary by sex, geography, and phylogeny. The geographic range of Xanthomicrogaster is strictly Neotropical, apparently restricted by the Sierra Madre del Sur range in Mexico and the Andes between Argentina and Chile. In addition, the genus Xanthomicrogaster occurs in Trinidad, but it is unknown if its range extends to the island of Tobago or beyond. In terms of elevation, specimens of Xanthomicrogaster have been collected from 13 m to 1600+ m. This revision increases the knowledge about Xanthomicrogaster, synthesizing research from the past 100 years and setting the stage for future taxonomists to examine the group