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Identification Tip: On the female, at the very tip of T6, (thus the very end of the upperside of the abdomen) there is located a peg- or knob-like projection that is distinctly upturned, sometimes hidden among the hairs, but very obvious under the microscope. Males a set of enlarged pits on T3 that are about 3-4 times the size of the surrounding pits, these pits are located about halfway between the sides and the centerline. These pits can be a bit difficult to detect due to the general business of the pitting of the segment. It is not clear whether these are absolutely distinctive for this species, but we know of no other species with them at this time.
Reprinted with permission from: Mitchell, T.B. 1962 Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 152.
FEMALE—Length 8-13 mm.; black, tegulae testaceous-hyaline and legs more or less reddened; eyes subparallel; lateral ocelli sub- equally distant from margin of vertex and each other, very slightly more distant from eyes; cheeks much narrower than eyes, carinate posteriorly, angulate below, but this area obscured with short, dense pubescence; clypeus very slightly convex, apical margin about straight, with a fringe of short but dense pubescence; middle tooth of mandible very low and inconspicuous; median length of labrum somewhat greater than basal width; punctures coarse and deep, separated to some degree on vertex and cheeks above, becoming irregular and rather sparse and obscure below, coarse and subcontiguous below ocelli, more finely rugoso-punctate on supraclypeal area and clypeus; pubescence entirely pale, very short, quite dense along sides of face and on cheeks below, forming anterior and posterior marginal fringes on pleura, scutello-mesothoracic suture with a tomentose line, and scutum with pair of anterior transverse, tomentose lines which are widely interrupted medially, propodeum with more elongate but rather thin pubescence; transverse carina of tubercles erect and quite conspicuous, extended slightly along anterior margin of scutum; posterior margin of scutellum slightly outcurved, posterior face quite sharply distinct from dorsal face; axillae acute but quite short, extending but very slightly beyond limits of scutellum; front coxal spines reduced to low carinate tubercles; wings subhyaline basally, becoming rather deeply infuscated over apical half, recurrent veins reaching 2nd submarginal cell subequally distant and quite near, base and apex; punctures coarse, close and deep over most of scutum, scutellum and axillae, slightly separated only in scattered areas on disc of scutum; pleura shining, punctures shallow but quite coarse, well separated below, becoming rather close just below tegulae, lateral faces of propodeurn smooth but dull, with barely perceptible, minute, scattered punctures, posterior face somewhat more shining,with much closer but very fine and vague punctures, dorsal area velvety, becoming deeply, irregularly striate along upper margin; concave area of basal abdominal tergum subcarinate and with a distinct and complete white fascia, apical margin of tergum slightly depressed and with a complete white fascia, punctures rather sparse medially becoming somewhat closer at sides; transverse groove of terga 2 and 3 rather shallow, submedian in position, obliterated medially, area basad of the groove coarsely and rather sparsely punctuate near middle, becoming quite closely punctate toward sides, apical part nearly impunetate across the broad median area, but with some rather close punctures toward the sides, apical margin depressed and white fasciate; terga 4 and 5 with hardly perceptible median grooves that are entirely obliterated medially, punctures relatively close toward base, more sparse toward the apex of each plate, apical margins rather abrupt and deeply depressed and white fasciate; tergum 6 triangular in outline, the sides nearly straight, basal half somewhat shining but very closely and rather finely punctate, apical half rather abruptly depressed on each side of median line, densely tessellate, without evident punctures and with numerous erect hairs, tip acute and usually slightly upturned (fig. 65); sternum 6 nearly parallel-sided on basal portion, apex triangularly pointed, with a dense fringe of short pubescence; sterna 1-4 shining, deeply, coarsely punctate, the punctures well separated or almost sparse in center, becoming quite close toward the sides, apical margins rather broadly but shallowly depressed, these areas yellowish-hyaline and white fasciate; sternum 5 triangularly acute apically, somewhat shining, punctures not as coarse as the preceding plates, well separated medially, becoming close laterally, margins shallowly depressed but dark, with a very obscure, apical fringe of short hairs.
MALE—Length 7-12 mm.; black, tegulae testaceous-hyaline, legs more or less reddened; eyes very slightly convergent below; lateral ocelli subequally distant from eyes, margin of vertex and each other; cheeks much narrower than eyes, carinate posteriorly, with a broad, shallow, concave area beneath which it is bare, somewhat shining and obscurely reticulate; clypeus very slightly convex, apical margin about straight, with a dense fringe of short, white pubescence; middle tooth of mandibles low but distinct; median length of labrum very slightly greater than basal width; punctures coarse and deep, well separated but not sparse across vertex, somewhat closer but shallow and indefinite on cheeks, face below ocelli coarsely rugoso-punctate, becoming finely so below antennae and over clypeus; pubescence entirely pale, quite short, thin in large part, rather copious below ocelli, around antennae, on sides of face and on clypeus, very short and rather dense on cheeks above, becoming very dense along lower orbits and on hypostomal area; pleura with anterior and posterior marginal fringes of white hairs, the scutello-mesothoracic suture finely white tomentose, and scutum with a pair of anterior transverse lines of white tomentuni that are widely interrupted medially; propodeum with more elongate, thin, whitish pubescence; transverse carinae of tubercles erect and rather conspicuous, extended slightly along anterior margin of scutum; hind margin of scutellum very slightly outcurved, posterior face not sharply dilferentiated from dorsal face; axillae quite slender and elongate, projecting rather conspiculously from limits of scutellum, tips not reaching beyond the posterior margin medially; coxal spines reduced to carinate, triangular tubercles; wings subhyaline basally. becoming rather deeply clouded over apical half, recurrent veins reaching 2nd submarginal cell about equally distant from base and apex; punctures coarse, deep and close over entire scutum, scutellum and axillae, being slightly separated only in center of scutum; pleura shining, punctures rather well separated but irregular below, becoming quite close just below tubercles; lateral faces of propodeum quite smooth but dull, without distinct punctures, posterior face more shining, with scattered, very fine and shallow, obscure punctures, dorsal area velvety, becoming narrowly and finely substriate along upper margin; concavity of basal abdominal tergum subcarinate, with a complete but narrow, white fascia, apical margin of tergum slightly depressed, with an entire, narrow, white, apical fascia which becomes rather dense laterally, punctures well separated but not sparse over entire disc; transverse grooves obliterated medially, submedian in position on tergum 2, more basal on 3 and 4, punctures well separated and rather evenly distributed across the bases of these terga, area just beyond the transverse grooves of 2 and 3 rather broadly impunctate, but becoming quite numerous and rather fine toward the depressed apical rims, these yellowish-hyaline and white fasciate; tergum 4 with somewhat finer, evenly distributed and well separated punctures, terga 3-6 more or less densely fasciate across the bases; tergum 6 very finely and closely punctate, deeply excavated in center of upper surface, dorsal protuberances very short, divergent, broadly rounded, the ventral spines more slender and elongate, slightly divergent (fig. 66); sterna 1-4 shining between coarse, deep and rather close punctures, apical margins rather broadly depressed, yellowish-hyaline and white fasciate; sternum 4 with a shallow, median, apical emargination; sternum 5 largely hidden, apical margin broadly and rather deeply incurved, almost emarginate; sterna 6 and 8 entirely retracted, 8 rather broadly rounded apically; penis valves about equal to gonocoxites in length, the gonocoxites quite slender, narrowly rounded at tip, bearing numerous, elongate, pale hairs.
DISTRIBUTION — Nebraska to Quebec and the New England states, south to Texas and Florida; March to August.
FLOWER RECORDS — Aster, Ceanothus, Helianthus, Melilotus and Rhus. Michener (1947) records it on Chrysopsis, and Robertson (1929) lists the following: Campanula, Lepachys, Lythrum, Psoralea, Pycnanthemum and Verbena.
HOSTS — Megachile (Megachile) centuncularis (L.) and M. (Chelostomoides) campanulae wilmingtoni Mitch.
Graenicher (1927) reported rearing C. modesta from nests of Megachile infragilis (centuncularis), but neither the host nor parasite specimens have been seen by this writer. A specimen of modesta reared from the nest of M. (Chelostomoides) campanulae wilminytoni by K. V. Krombein has been seen, however, as well as a specimen of the host from the same nest. This seems to be a rather wide divergence of hosts for parasite species, and indicates a need for additional data.
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