The following material taken with permission from: Mitchell, T.B. 1962. Bees of the Eastern United States, Volume II. North Carolina Agricultural Experiment Station. Tech. Bul. No.152, 557 p.
In Ptilothrix the vertex is broadly convex (as in Melitoma), the clypeus is black in both sexes, and in the front wing the marginal cell is acute apically, slightly bent away from the coastal margin. There are three submarginal cells, the 2nd shorter than the 1st or 3rd. The basal segment of the flagellum is shorter than the scape, and barely equal to segments 2 and 3 combined, in both sexes. The arolia are absent. In the female, the scopa of the hind tibiae and the basitarsi is of finely plumose, elongate hairs.
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 13-17.5 mm., breadth of abdomen 5-7 mm.; black, including mandibles, antennae and legs, spurs brownish-testaceous, tegulae yellowish-hyaline; wings uniformly, rather lightly infuscated, veins brownish to piceous; cheeks somewhat narrower than eyes; clypeus somewhat protuberant, its median length considerably greater than half the distance between eyes; eyes subparallel; mandibles with a small, inner, subapical angle, apical half largely testaceous on outer surface in some specimens; basal segment of flagellum slightly longer than segments 2 and 3 combined, these no longer than broad; punctures of clypeus quite coarse and deep, rather sparse medially, becoming somewhat finer and closer at each extreme side; median length of lab- rum about half the breadth, rather broadly rounded apically, margin much thickened, surface shining between rather fine, deep, slightly separated punctures, these becoming crowded laterally and apically; lateral areas of face below antennae shining, very minutely punctate, punctures somewhat separated, median area much more coarsely and closely punctate, upper part of face below level of ocelli shining, punctures quite coarse, deep, well separated but hardly sparse on each side, becoming somewhat closer medially below anterior ocellus; surface between lateral ocelli and eyes shining and impunctate; vertex rather closely punctate posterior to ocelli, the punctures becoming finer and more sparse on the shining cheeks posteriorly; punctures of scutum fine but deep and distinct, quite uniformly close throughout; pleura somewhat shining between coarser, deeper, slightly separated punctures, these becoming closer above; posterior face of propodeum shining, punctures fine and quite sparse, dorsal area with minute and quite uniformly close punctures, lateral faces finely and rather deeply punctate, the punctures quite close anteriorly, rather sparse and minute posteriorly and below; discs o abdominal terga very minutely and closely punctate throughout, only the very narrow, apical rims impunctate; pygidium elongate triangular, apex rather narrowly rounded; pubescence rather short and erect on head and thorax, pale yellowish above antennae and along margin of eyes, clypeus largely bare, labrum with a quite dense, yellowish, apical fringe, vertex with more elongate pale ochraceous pubescence, and cheeks with rather elongate hairs below; entire thorax quite densely covered with pale ochraceous pubescence, obscuring the surface in large part; legs largely black pubescent, but front femora with a posterior fringe of elongate, pale ochraceous hairs; hind tibial scopa black, the hairs short plumose; basal abdominal tergum with some very obscure, rather short, pale pubescence anteriorly, disc otherwise covered with short, suberect, fuscous or blackish pubescence; remaining terga quite densely covered with very short, erect, entirely black pubescence, that on the more apical terga becoming somewhat elongate laterally.
MALE—Length 12.5-17.5 mm., breadth of abdomen 5-6.5 mm.; black, the mandibles more or less yellowish-testaceous apically, spurs brownish-testaceous, tegulae testaceous-hyaline; wings rather uniformly infuscated, veins brownish to blackish; cheeks subequal to eyes in width; clypeus only slightly protuberant, its median length somewhat less than half the distance between eyes; eyes subparallel; outer margin of mandibles somewhat angulated at base, without distinct inner teeth; median length of labrum slightly more than half the width, broadly rounded apically, margin slightly thickened; basal segment of flagellum as long as segments 2 and 3 combined; clypeus and labrum somewhat shining, quite finely and closely punctate; lateral areas of face below level of antennae very minutely and quite closely punctate, surface above rather uniformly, finely punctate, punctures slightly separated below ocelli, becoming minute and sparse above, space between ocelli and eyes shining and nearly impunctate, vertex minutely and rather closely punctate; cheeks shining, with minute, rather widely separated punctures; scutum and scutellum somewhat shining beneath dense pubescence, punctures very fine and rather close, punctures of pleura quite deep and distinct but very fine and close throughout; posterior face of propodeum below somewhat shining, punctures minute, rather widely separated, dorsal area somewhat less shining, punctures closer, becoming very close at extreme sides, lateral surfaces shining, punctures fine but rather deep and distinct, well separated but hardly sparse; abdominal terga quite uniformly, closely and very minutely punctate throughout, the apical, impressed areas obscurely yellowish-hyaline beneath dark pubescence; pubescence short but rather dense over most of face, entirely pale ochraceous; quite dense between antennae and posterior to ocelli, somewhat thinner across vertex and on cheeks anteriorly; thorax uniformly, densely covered with short, pale ochraceous pubescence; coxae and trochanters largely pale pubescent, but legs otherwise with short blackish pubescence; basal abdominal tergum with very short, dense, pale ochraceous pubescence anteriorly, this becoming brownish dorsally, darker toward apical margin, the following terga densely covered with very short, erect, black pubescence; sterna 7 and 8 and genital armature as shown (fig. 70).
DISTRIBUTION—Kansas to New Jersey, south to Texas and Florida, June to August.
FLOWER RECORDS—Hibiscus. Robertson (1929) records this species on Cephalanthus, Cirsium, Ipomoea, Verbena and Vernonia.