Abstract
A new subgenus, Alocanthedon Engel and Gonzalez subgen. n., is described for five species of unusual Southeast Asian bees in the genus Chalicodoma Lepeletier de Saint Fargeau (Megachilinae: Megachilini). The subgenus is most noteworthy for the deep postgenal depression or furrow in males (bordered outwardly near the base of the mandible by a protuberant, thick lamella) and the presence of a dense patch of black setae posteriorly in the forewing medial cell (except in one species) [resembling the dense patch of setae among the submarginal cells of Thrinchostoma Saussure (Halictidae: Halictinae: Halictini)]. The subgenus is characterized and distinguished from the related Callomegachile Michener. A key to the following five species presently included in the subgenus is provided: Chalicodoma aterrimum (Smith), Chalicodoma atratiforme (Meade-Waldo) comb. n., Chalicodoma memecylonae Engel sp. n., Chalicodoma odontophorum Engel sp. n., and Chalicodoma apoicola Engel sp. n. Chalicodoma (Callomegachile) atratiforme sininsulae (Cockerell) is newly placed in synonymy with C. (C.) fulvipenne (Smith). Species have been collected from Memecylaceae (Myrtales) and Fabaceae (Fabales). The phylogenetic relationships of Alocanthedon among other Megachilini are briefly elaborated upon.
Highlights
The Southeast Asian fauna of megachiline bees is diverse but simultaneously poorly documented, underrepresented in collections, and with many species largely confused
Tree search in Tree analysis using New Technology (TNT) was done by implementing sectorial searches (SS) with tree drifting (TD) and tree fusing (TF) and ratchet runs with TD and TF
The deep postgenal depression in males having a distinctly protuberant, thick lamella next to the mandible, procoxa with oblique carina or lamella medially on disc, mesobasitarsus with the inner surface concave basally, and the distinctly long, narrow gonostyli of the genitalia are apomorphic characters within Chalicodoma. Such characters are distinctive enough to support the separation of those species into a new subgenus
Summary
The Southeast Asian fauna of megachiline bees is diverse but simultaneously poorly documented, underrepresented in collections, and with many species largely confused (especially in the diverse subgenus Eutricharaea Thomson of Megachile Latreille). The only other group of bees known to have a similar patch of black setae on the forewing is the sweat bee genus Thrinchostoma Saussure (Halictidae: Halictinae: Halictini). The relationships among the seven subgenera presently recognized in Chalicodoma (Callomegachile Michener, Cestella Pasteels, Chalicodoma s.str., Cuspidella Pasteels, Gronoceras Cockerell, Largella Pasteels, and Pseudomegachile Friese) need to be studied in detail. Such subgenera are highly diverse, morphologically heterogeneous, and as distinct as many genera of bees.
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