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Extracted with permission from: Onuferko, T.M. 2017. Cleptoparasitic Bees of the Genus Epeolus Latreille (Hymenoptera: Apidae) in Canada. Canadian Journal of Arthropod Identification No. 30: March 30, 2017. doi:10.3752/cjai.2017.30
http://cjai.biologicalsurvey.ca/o_30/o_30.html
Diagnosis. Among Canadian species, E. minimus most closely. resembles E. olympiellus, and the two can be difficult to distinguish from one another where their ranges overlap. Epeolus minimus can be readily distinguished from all other Epeolus in Canada except E. olympiellus by the following combination of features: F2 of female at least 1.2 x as long as wide; mesoscutum with paramedian band (if not entirely obscured by pale tomentum); mesopleuron closely and evenly punctate; axilla with lateral margin relatively straight, axilla with tip clearly separated from lateral margin of mesoscutellum and not extending much beyond midlength of mesoscutellum; axilla (except perhaps tip) and mesoscutellum all black; and T2 with fascia with anterolateral extensions of tomentum. E. minimus typically exhibits reddish orange colouration on the labrum (apically or entirely), antenna, and quite extensively on the legs. In E. olympiellus, the fasciae of T3 and T4 are typically entirely broken or greatly narrowed laterally, a state not observed in specimens of E. minimus.
Distribution in Canada: Known to occur in most of Canada except parts of the Atlantic and high Arctic regions (Map 10).
E. minimus and E. banksi are practically indistinguishable - except by location. In Mitchell�s key (1962), he listed the following as differences between the males of these two species. E. Minimus: Mandibles with an acute, inner tooth which is slightly nearer apex than base; mid and hind legs largely ferruginous. E. banksi: Mandibles with a more obtuse, submedian, inner angle; legs largely dark, only the tarsi somewhat reddened. The females are noted to be different in the sculpting of the mesopluera, especially on the lower half. I, however, have either NOT found these differences to be as said or they are not consistent. I have not been able to see a marked difference between the mandible structures in the males. The leg color character does seems to be follow a trend. However, it would be difficult to identify without specimens for comparison as the color difference is slight and the legs of both species are to some degree reddened. Also, the mesopleura character in the females is not consistent, the patterns being too similar to be the basis of dependable identification.
One difference that does seem to be rather consistent is the color of the antennae in the females. E. banksi females have very dark brown antennae with very subtle, if any lightening, anywhere on the antennae. E. minimus females have lighter antennae overall, being a medium brown color, with significant lightening on part of F1 and on the base and apex of the scape. This is not so in the males, at least not to the same extent. In the males, the punctation pattern on the pygidial plate seems to be a rather dependable character. In E. banksi the pits are obvious, moderately deep, and quite dense, though not touching. In E. minimus the pits are shallow and quite sparse, not so noticeable as in E. banksi. In E. minimus the pygidial plate also tends to be lighter in color than the rest of the terga, while in E. banksi it tends to be quite dark, similar to the color of the terga.
Use these characters to support your locality based identification of these two species.
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