Taxonomic notes on the small resin bees Hypanthidioides subgenus Michanthidium (Hymenoptera, Megachilidae)

Abstract As part of ongoing investigations on anthidiine bees, the type of Anthidium albitarse Friese was found to be conspecific with one of the two species of the small resin bees Hypanthidioides subgenus Michanthidium. The new combination, Hypanthidioides (Michanthidium) albitarsis, is the oldest name, resulting in Gnathanthidium sakagamii Urban as a new junior synonym. The previously unknown male of the second species, Hypanthidioides ferrugineus, is described and figured, including the genitalic structure and associated sterna. Males and females of Hypanthidioides ferrugineus have been collected from flowers of Cuphea sp. (Lythraceae).


Introduction
The Neotropical anthidiine bee genus Hypanthidioides Moure (sensu Michener 2007) contains 51 species grouped into 10 subgenera (Michener 2007;Ascher and Pickering 2011) that are treated at the generic level in the classification of Urban and Moure (2007). Some subgenera are monotypic or contain a few species (Table 1) with unusual characters related to adaptations for pollen collecting (e.g., modified hairs on the mouthparts) or secondary sexual characters (e.g., spines on the hind coxa of the male). In the absence of a phylogenetic analysis it seems preferable to show their relationship by placing them within an inclu-sive taxonomic category, such as Hypanthidioides, rather than separating them in multiple genera. If future studies show that Hypanthidioides sensu lato constitutes a monophyletic group or users decide to continue to follow Michener's classification, a few homonyms created by such a change need to be corrected, as indicated by Ascher and Pickering (2011).
Hypanthidioides s.l. is easily recognized by its small (length 5-9 mm) and usually slender body, the presence of juxtantennal carinae, and the absence of a preoccipital carina in both sexes. Little is known about the biology of these bees. The nests, only known for two species, one each in the subgenera Dicranthidium and Hypanthidioides s. str., are made of resins and are built inside empty cavities or entirely exposed, attached to stems or twigs (Schrottky 1902;Laroca and Rosado-Neto 1975). Although floral relationships are largely unknown in Hypanthidioides, the presence of curved or hooked hairs on the labiomaxillary complex in species of the subgenera Michanthidium and Larocanthidium suggest a special floral relationship (Michener 2007). Similar modified hairs occur in other unrelated bees and are used to extract pollen from tubular flowers with hidden anthers, such as those in the plant families Boraginaceae and Verbenaceae (e.g., Thorp 2000).
As part of a revision of Anthidium Fabricius, we examined the type of Anthidium albitarse Friese, 1917. The male specimen is labeled San Jose, Costa Rica, and agrees with the original description of Friese (1917). It proved not to be a species of Anthidium, but rather to belong to Hypanthidioides subgenus Michanthidium (Figs. 1-5). Michanthidium was described by Urban (1993) as Gnathanthidium, a name she subsequently replaced to avoid the junior homonymy with the African Gnathanthidium Pasteels (Urban 1995). The two species currently known in Michanthidium, H. sakagamii (Urban) and H. ferrugineus (Urban), occur in southern Brazil and northern Argentina; the latter is known only from the female. Here we present the taxonomic changes to Hypanthidioides (Michanthidium) resulting from the inclusion of Anthidium albitarse, and describe for the first time the male of H. ferrugineus. Morphological terminology follows that of Michener (2007). The abbreviations S and T are used for metasomal sterna and terga, respectively. Institutional acronyms used herein are: BBSL, U.S. National Pollinating Insects Collection, Bee Biology and Systematics Laboratory, Utah State University, Logan, UT; DZUP, Departamento de Zoologia, Universidade Federal do Paraná, Table 1. Subgenera of Hypanthidioides sensu Michener (2007). Number of species according to Urban and Moure (2007).  Urban, 1995Urban, [1994: 281. Nomen novum pro Gnathanthidium Urban, 1993.

Comments.
Michanthidium is most similar to the subgenus Larocanthidium, from which it can be separated by the following characters: female mandible without distinct carinae on outer surface, without a strong basal tooth separated from mandibular margin by a deep emargination; male T6 without distal margin expanded, elevated, or bilobed medially. In the key to the subgenera of Hypanthidioides (Michener 2007), the presence of a hind coxal spine in the male is one of the characters that separates Michanthidium from Larocanthidium. However, this spine is not present in the male of H. ferrugineus and therefore should be removed from the key.  (Figs 4 and 5). The female can be further recognized by the absence of a median spine on the preapical carina of T6. Additional characters that distinguish the male include: hind coxa with midapical spine (Fig. 3), S2-S4 with incomplete, poorly developed premarginal hair bands, T6 with small sublateral spine (barely visible in Fig. 5), and T7 without median spine (Fig. 5). Comments. Michanthidium is currently known from southern South America; the holotype of H. albitarsis, if from Costa Rica, would considerably extend its geographi- cal distribution. Such an expansion is possible considering that other bee genera, such as Duckeanthidium Moure and Michener, previously thought to be restricted to South America, have been recently found in Central America (Michener 2002). Alternatively, it might represent a mislabeled specimen because other examples of inaccurate locality labels on specimens in the Friese collection exist. For example, Dasycolletes ventralis Friese (now in the colletid genus Leioproctus Smith) is a South American species described by Friese from Sydney, Australia (Michener 2007: 154). Further support for mislabeling comes from the absence of Michanthidium in more than 38,000 specimens of bees from Costa Rica that we have examined.

Hypanthidioides
Distribution. Hypanthidioides albitarsis is known from southern Brazil and adjacent Argentina Urban (1993). Additional records are from the departments of Iguazú, Veinticinco de Mayo, and Candelaria in the Province of Misiones, Argentina (see below).
Head and mesosoma including coxae, anterior surfaces of hind trochanter and femur coarsely punctate, punctures about one-fourth to one-third width of median ocellus except finely punctate on pronotum, omaulus, metepisternum, most of propodeum and remainder of legs; terga as coarsely punctate as scutum with wide, impunctate, translucent, apical margins on T1-T6.