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A revision of the Nearctic Melittidae: the subfamily Melittinae (Hymenoptera: Apoidea). (1995). Contributions in Science, 451, 25-26. https://doi.org/10.5962/p.208086
This species most closely resembles M. americana; both sexes are separable by the much sparser punctation of the mesoscutum, scutellum, and basal metasomal terga, as noted in the key. From the other three North American species, M. eickworti is separable by the features noted in the key.
DESCRIPTION
FEMALE. Measurements (mm). Head width 2.9-3.3, head length 2.6-2.8, wing length 7.7-8.5, total length 10.5-12.1.
Structure and Punctation. Head. 1.12-1.19 times as broad as long; inner eye margins slightly divergent below, upper interocular distance 0.86-0.93 times lower interocular distance; in frontal view, vertex margin strongly arched above ocelli, distance from ocelli to margin distinctly greater than diameter of anterior ocellus. Interocellar distance slightly greater than diameter of anterior ocellus; ocellocular distance about 2 times diameter of anterior ocellus. First flagellar segment about 2 times diameter of anterior ocellus. First flagellar segment distinctly longer than broad and about one-third longer than second segment, second segment distinctly broader than long.
Basal two-thirds (approximately) of clypeus densely tessellate and slightly shiny between moderate punctures (about 0.05 mm diameter) that are mostly separated by about one puncture diameter or less, but with narrow, median, nearly impunctate line; apical one-third with broader impunctate area, median portion lightly tessellate and somewhat shiny, grading to smooth and shiny toward sides. Paraocular area shiny between fine (0.03 mm diameter) to moderate punctures that are mostly subcontiguous, but with irregular interspaces exceeding a puncture diameter. Frons densely tessellate and dull, punctures fine and obscure, mostly separated by one puncture diameter or less; side of face shinier and less sharply tessellate between fine close to sparse punctures; vertex with shiny, nearly impunctate area between ocelli and eyes, otherwise tessellate and slightly shiny between fine, mostly subcontiguous punctures; gena slightly shiny, densely tessellate between sparse, obscure, fine punctures.
Mesosoma. Middle one-half or more of mesoscutum shiny and polished between moderate punctures separated by 1.0-2. 5 puncture diameters, punctures becoming subcontiguous only anteriorly and laterally, where interspaces become more or less distinctly tessellate and dull. Scutellum shiny, with scattered fine punctures on anterior two-thirds; posterior one-third, and along midline nearly to base, subcontiguously to contiguously punctate with moderate punctures. Mesepisternum dull and sharply tessellate between subcontiguous to contiguous moderate punctures. Metepistemum moderately shiny and less sharply tessellate, virtually impunctate. Side of propodeum anteriorly similar to metepistemum, becoming dull and subcontiguously punctate distad; basal area with irregular, widely spaced rugulae anteriorly, interspaces moderately shiny, remaining area distinctly tessellate and less shiny; disc slightly shiny, reticulate-punctate.
Wings transparent, slightly brownish, darker beyond cells; stigma and veins light brown.
Metasoma. Tergum 1, anterior to marginal impunctate band with a narrow zone of sparse, moderate, piligerous punctures, basad of which disc is smooth and shiny between widely scattered fine punctures; disc of tergum 2 smooth and shiny between sparse to scattered minute to fine punctures; tergum 3 similar to second, but some punctures moderate in size; tergum 4 smooth and shiny between scattered, moderate punctures; tergum 5 slightly shiny and distinctly tessellate between subcontiguous to close, moderate punctures.
Pilosity. Mostly whitish, somewhat yellowish on sides and apical margin of clypeus and on lower gena; yellowish red on mandible; hairs of mesoscutum mostly pale but with sparse blackish hairs; those in center entirely blackish, but no dark hairs between parapsidal line and margin; scutellum largely pale pubescent, but a few blackish hairs in center.
Metasomal tergum 1 without definite preapical band of pale hairs; terga 2-4 with narrow apical bands
of appressed, white, plumose hairs that are weak or interrupted at middle; discal hairs short, simple,
and pale on terga 2-4, long, plumose, and blackish on terga 5 and 6.
Color. Head and body blackish, legs dark brownish; flagellum dark reddish brown beneath; tegula
clear yellowish.
MALE. Measurements (mm). Head width 2.5-2.9, head length 2.4-2.7, wing length 7.0-8. 1.
Structure and Punctation. Head. 1.03-1.11 times as long as broad; inner eye margins slightly convergent below, upper interocular distance 1.03-1.06 times lower interocular distance; in frontal view, vertex margin strongly elevated behind ocelli, distance from ocelli to margin distinctly greater than diameter of anterior ocellus. Interocellar and ocellocular distances about 2 times diameter of anterior ocellus. First flagellar segment about 0.75 times length of second, second about 0.80 times length of third.
Clypeus finely rugosopunctate but with shiny, narrow, impunctate median line and transverse impunctate preapical band. Supraclypeal area subcontiguously punctate, grading to slightly larger, dense punctures on frons; punctures of paraocular area mostly subcontiguous, interspaces shiny; preoccipital area similar but interspaces lightly tessellate; vertex, adjacent to lateral ocelli, with large, smooth, shiny, impunctate area.
Mesosoma. Similar to that of female, but mesoscutum almost entirely smooth and shiny, without anterior and lateral zones of subcontiguous punctures.
Wings as described for female.
Metasoma. Similar to that of female. Hidden sterna and genitalia similar to those of M. americana but differing as illustrated (Figs. 3, 4, 10, 18), but apical disc of sternum 8 concave and with distinct longitudinal median impression.
Pilosity. Similar to that of female, but clypeus hidden beneath dense prostrate plumose hairs and
face generally with hairs denser and longer; vertex and gena with some long, fuscous hairs among the
pale hairs; center of mesoscutum with few or no fuscous hairs; hair bands of metasomal terga 2-4
very weak and interrupted in middle; terga 5-7 largely dark pubescent, without pale hair bands,
but with some pale hairs at sides.
Color. Similar to that of female.
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