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 Hypanthidioides ferrugineus and therefore should be removed from the key.

Hypanthidioides albitarsis differs from Hypanthidioides ferrugineus in the finer punctures on the scutum, scutellum and terga (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).

Michanthidium is currently known from southern South America; the holotype of Hypanthidioides albitarsis, if from Costa Rica, would considerably extend its geographical 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 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).

(n = 12♀, 8♂) 10♀, 7♂; Argentina: Misiones, Cataratas del Iguazú, 5.9.XI.1970, C. Porter, L. A. Stange; remaining specimens also from Misiones but from the following localities: 1♀, Loreto, A. A. Oglobin; 1♀, Dos de Mayo, 12.73, Fritz; 1♂, San Javier, 20.XI.1973, Willink-Tomsoc (BBSL, FSCA).

This species can be easily separated from Hypanthidioides albitarsis by the coarser punctures on the scutum, scutellum and terga (compare Figs 4 and 6), small median spine on the preapical carina of female T6, and the following characters in the male: T6 without small sublateral spines, T7 with acute lateral and median spines (Fig. 7), hind coxa without midapical spine, with a short row of black, thick short hairs on median margin (Fig. 8), and S2–S4 with complete, well-developed premarginal hair bands.

Male: Body length, 8.2mm; forewing length, 5.5 mm. Structure.Hind coxa ventrally without apical spine on median margin; hind trochanter carinate medially. T6 without sublateral spines or protuberances; T7 with acute lateral and median spines (Fig. 7); S5 and S6 each with small lateral spine; S7, S8 and genital capsule as in Figs 9–11.

Head ferruginous including antennal scape and pedicel except: dark reddish brown on mandible, inferior gena and distal flagellomeres; black on labrum, ocellar and torular areas; yellow on clypeus and inferior paraocular area. Mesosoma black except: ferruginous on tegula and legs excluding coxae (trochanters and femora variably darkened); yellow on pronotal lobe, tegula anteriorly, scutum on anterior and lateral margins, axilla, scutellum on distal margin, coxae. Metasoma dark reddish brown, lighter on sterna except T1, T3, T5, T7 and S2–S4 each with complete yellow band, remaining terga maculate laterally. Wings brownish, darker on anterior margin including marginal cell; veins, stigma and prestigma dark brown.

Pubescence whitish except yellowish on inner surfaces of tarsi; hairs long, dense, distinctly plumose on paraocular area, pronotal lobe, mesepisternum and metepisternum ventrally, lateral surface of propodeum, inferior margin of fore femur, premarginal areas of S2–S4; hind coxa with distinct row of stout black hairs medially on ventral surface (Fig. 8).

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.

(n = 5♀, 8♂) 5♀, 6♂; Argentina: Prov. Tucumán, Tacanas, 10-XII-1977, L. A. Stange. Flowers, Cuphea sp. [Lythraceae]; two other males with the same data but collected on November and December of 1968 (BBSL, FSCA).

Both males and females of this species have been collected on flowers of Cuphea sp. (Lythraceae).