Herein, the cleptoparasitic (cuckoo) bee genusEpeolus(Hymenoptera: Apidae) is revised for species occurring in North America, north of Mexico, and an updated checklist of all species known to occur in Canada and the United States of America is provided with comprehensive descriptions, diagnoses, and a single dichotomous key (using the same couplets for both sexes) to aid in their identification. To increase their recognition among North American naturalists, English common names are also proposed for all North AmericanEpeolus. A total of 43 species is confirmed as present in the region, 15 of which are newly recognized. The following new species are proposed based on unique morphological (and in most cases also molecular) attributes:E.andriyisp. n.,E.attenboroughisp. n.,E.axillarissp. n.,E.basilisp. n.,E.brumleyisp. n.,E.chamaesarachaesp. n.,E.deyrupisp. n.,E.diadematussp. n.,E.ferrariisp. n.,E.gibbsisp. n.,E.inornatussp. n.,E.nebulosussp. n.,E.packerisp. n.,E.splendidussp. n., andE.tessierissp. n.Of the 15, six (E.axillaris,E.brumleyi,E.chamaesarachae,E.diadematus,E.splendidus, andE.tessieris) were identified as new species under different names (nomina nuda) in an M.Sc. thesis by Richard L. Brumley in 1965, but until now they have not been formally described. Detailed morphological comparisons with some evidence from DNA barcoding support the following synonymies, one of whichCwas first proposed by Brumley (1965): a)E.melectimimusCockerell and Sandhouse,syn.n., underE.asperatusCockerell; b)E.crucisCockerell,syn.n., underE.compactusCresson; c)E.mesillaepalmarumLinsley,syn.n., underE.mesillae(Cockerell); and d)E.weemsiMitchell,syn.n., and e)E.vernalisMitchell,syn.n., underE.ilicisMitchell. Only one member of the almost entirely Neotropical “Trophocleptria group” (EpeolusbifasciatusCresson) is confirmed as occurring north of Mexico, and is widespread East of the Rocky Mountains. Known floral associations are indicated for each species, as are suspected or known host species ofColletesLatreille. Evidence is presented that suggests further investigation into the possible synonymy ofColleteswickhamiTimberlake underC.scopiventerSwenk is warranted.
