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Extracted from: Onuferko TM (2018). A revision of the cleptoparasitic bee genus Epeolus Latreille for Nearctic species, north of Mexico (Hymenoptera, Apidae). ZooKeys 755: 1–185. https://doi.org/10.3897/zookeys.755.23939
Diagnosis. The following morphological features in combination can be used to tell
E. rufulus apart from all other North American Epeolus except E. attenboroughi: the
mandible has a blunt, obtuse preapical tooth; the preoccipital ridge does not join the
hypostomal carina; the mesoscutum is covered in pale tomentum, which is densest
anteromedially; the axilla is elongate, extending well beyond the midlength of the mesoscutellum but not as far back as its posterior margin, and the free portion is distinctly
hooked; the mesopleuron is closely (most i<1d) and evenly punctate; and T1–T4 have
complete apical fasciae. Whereas in E. attenboroughi T1 has a comparatively narrow
discal patch (the longitudinal band is more than half as wide as the breadth of the apical fascia in dorsal view) and in females F2 is not noticeably longer than wide, in E.
rufulus the discal patch is so wide that the longitudinal band is barely visible in dorsal
view and in females F2 is more than 1.2 × as long as wide. Epeolus rufulus is also similar to E. ainsliei in that in both species the axilla is dilated laterally and the free portion is
distinctly hooked, and the T1–T4 apical fasciae are complete; however, in E. ainsliei
the mandible is simple, the preoccipital ridge joins the hypostomal carina, and the
mesoscutum has distinct paramedian bands.
Redescription. FEMALE: Length 7.6 mm (difficult to gauge in holotype because
head detached and glued to collection label, and much of pronotum missing; given
instead for non-type specimen most similar in size); head length 1.9 mm; head width
2.6 mm; fore wing length >5.1 mm (margins of both very worn in holotype).
Integument coloration. Black in part, at least partially ferruginous on mandible,
labrum, clypeus, antenna, pronotal lobe, tegula, axilla, mesoscutum, mesoscutellum, metanotum, mesopleuron, metapleuron, propodeum, legs, metasomal terga
(including pygidial plate), and metasomal sterna. Mandible with apex darker than
all but extreme base; preapical tooth lighter than mandibular apex (difficult to see
in holotype; described from non-type specimen). Antenna brown and orange in
part. Pronotal lobe and tegula pale ferruginous to amber. Mesoscutum orange along
lateral margin and with pair of orange markings near posterior margin between midline and parapsidal line. Wing membrane subhyaline, apically dusky. Legs entirely
reddish orange (both forelegs missing in holotype, but entirely reddish orange in
non-type specimens).
Pubescence. Face with tomentum densest around antennal socket. Clypeus, upper
paraocular and frontal areas, and vertexal area mostly exposed. Dorsum of mesosoma
and metasoma with bands of off-white to pale yellow short appressed setae. Mesoscutum sparsely covered in pale tomentum. Mesopleuron with upper half sparsely hairy;
ventrolateral half nearly bare, except along margins. Metanotum with tomentum
rubbed off medially in holotype, but uninterrupted and uniformly off white in nontype specimens. T1 with discal patch quadrangular and very wide, the basal and apical
fasciae only narrowly joined laterally. T1 with basal and apical fasciae and T2–T4 with
apical fasciae complete, those of T2 and T3 somewhat broader laterally, T2 with fascia
without anterolateral extensions of tomentum. T5 with pseudopygidial area lunate, its
apex more than twice as wide as medial length, indicated by silvery setae on impressed
disc of apicomedial region elevated from rest of tergum. S5 with apical fimbria of coppery to silvery hairs extending beyond apex of sternum by ~2/5 MOD.
Surface sculpture. Punctures dense. Labrum and clypeus with punctures equally
dense (i<1d). Impunctate spot lateral to lateral ocellus absent. Mesoscutum, mesoscutellum, and axilla coarsely and densely rugose-punctate. Tegula very densely punctate
mesally (i<1d), less so laterally (i=1–2d). Mesopleuron with ventrolateral half densely
punctate (i<1d) to rugose; mesopleuron with punctures more or less equally dense
throughout. Metasomal terga with punctures very fine, dense (i≈1d), evenly distributed on disc.
Structure. Preapical tooth blunt and obtuse. Labrum with pair of small subapical
denticles not preceded by carinae. Frontal keel not strongly raised. Scape with greatest
length 1.9 × greatest width. F2 noticeably longer than wide (L/W ratio = 1.6). Preoccipital ridge not joining hypostomal carina, from which it is separated by no less than 1
MOD at its terminal (not visible in holotype because head detached and glued to collection label; described from non-type specimens). Mesoscutellum weakly bigibbous.
Axilla large, its lateral margin (L) more than half as long as mesoscutellar width (W)
(L/W ratio = 0.6) and tip extending well beyond midlength of mesoscutellum but not
as far back as its posterior margin; axilla with tip conspicuously diverging from side of
mesoscutellum, distinctly hooked, and axilla with free portion 2/5 its medial length;
axilla with lateral margin arcuate and carinate. Fore wing with three submarginal cells.
Pygidial plate apically truncate.
MALE: Description as for female except for usual secondary sexual characters and
as follows: F2 shorter, as long as wide (L/W ratio = 1.1); mesopleuron almost entirely
obscured by white tomentum; S4 and S5 with much longer coppery to silvery subapical hairs; pygidial plate apically rounded, with large deep, well-separated punctures,
with the interspaces shining.
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