New Species of Exomalopsis and Its Associated Cleptoparasite Nomada from Colombia with Description of the Nest (Hymenoptera: Apoidea: Anthophila: Apidae)

We describe two new species of bees from Colombia; one is a species of Exomalopsis found nesting in the city of Medellin, Colombia, (the host) and its cleptoparasitic bee, a species of the genus Nomada. In addition, we provide information on the nest architecture of the new species and provide data on occupancy by both the host bee and its cleptoparasite. We present an updated list of the species of Exomalopsis and Nomada of Colombia and taxonomic keys to the species of Exomalopsis. 1. Introduction Exomalopsis Spinola (Apinae: Exomalopsini) encompasses nearly 90 described species in four subgenera according to Michener [1]. The genus is only known from the Western Hemisphere and most of its diversity if found in the Neotropical and Nearctic regions. Timberlake [2] reviewed the species of the genus in the broader sense in the United States and later revised the species of North America [3]; more recently, Silveira [4] revised the phylogenetic relationships and classification of the tribe Exomalopsini and later described new species and designated lectotypes for previously described species of South America [5]. Nests of Exomalopsis are communal; the nests and nesting behavior of some species have been described (i.e., [6] on E. solani, Raw [7, 8] on E. globosa and E. similis, Rozen and Snelling [9] on E. nitens, and Zucchi [10] on E. auropilosa, but the nesting biology of most of the species remains unknown. Rozen [11] compared the nesting biology of several genera in the tribe Exomalopsini, including 12 species of Exomalopsis sensu lato, four of them in the nominal subgenera: E. auropilosa, E. globosa, E. similis, and E. fulvofasciata. In terms of the diversity of the genus in Colombia, there are currently four described species of Exomalopsis that are currently known (three in the subgenus Exomalopsis (E. auropilosa, E. digressa, and E. similis) and one in the subgenus Phanomalopsis (E. snowi)) in addition to an undetermined number of undescribed species according to Smith-Pardo [12], Smith-Pardo and Vélez-Ruiz [13], and Vélez-Ruiz [14]. In this paper, we describe a new species of bee in the genus Exomalopsis, subgenus Exomalopsis (host), and a new species of bee in the genus Nomada, a cleptoparasitic of the former. In addition, we present the description of the nest, provide some data on its occupancy, and provide a taxonomic key to the species of Exomalopsis currently known for Colombia. 2. Materials and Methods One nest was found, dissected, and described; all bees were collected inside or coming to the nest. It was located in the area around the