Reprinted with permission from: Mitchell, T.B. 1960 Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 141.
MALE�Length 4.5 mm.; black; antennae piceous above, ferruginous beneath; scape maculated anteriorly; mandibles and labrum black; tegulae ferruginous, maculated; wings subhyaline, veins and stigma brownish-ferruginous; maculations pale yellow, as follows:
entire face below antennae, supraclypeal mark elongated and rounded above, reaching level of upper margin of antennal fossa, lateral face marks abruptly constricted at lower edge of antennal fossa, produced narrowly upward, ending in a rounded knob just above antennae and widely separated from eye margin; scape with an elongate yellow mark anteriorly; tubercles, a pair of lines on collar, and a large anterior spot on tegulae, yellow; front tibiae yellow anteriorly, mid tibiae at extreme base, and basal half of hind tibiae; all spurs and basitarsi pale yellow, other tarsal segments reddish; legs otherwise piceous; face constricted below; cheeks narrower than eyes in lateral view; scape robust, diameter at apex considerably greater than that of flagellum; basal segment of flagellum about half as long as broad, these dimensions subequal on the 2nd and following segments; front coxae simple; dorsal area of propodeum slightly longer than metanotum, coarsely reticulate, posterior surface truncate, obscurely reticulate, subcarinate laterally, lateral surfaces finely rugose; punctures of scutum rather fine, but deep and distinct, rather close, but with shining interspaces evident; punctures of scutellum slightly larger and more widely separated; pleural punctures about the size of those on scutum, but more sparse, interspaces tessellate; abdomen quite deeply and distinctly though very finely punctate, rather sparsely so on basal segment medially, but otherwise quite close.
DISTRIBUTION � Minnesota, Wisconsin, Ontario and Connecticut; June, July and August. These records are based upon females and are thus somewhat uncertain. Metz records this species from Alabama, New Jersey and Canada, but whether or not these records were based on the more reliably determined males or not, is not known by this writer.
Reprinted from: Snelling, R. 1970. STUDIES ON NORTH AMERICAN BEES OF THE GENUS
HYLAEUS. 5. THE SUBGENERA HYLAEUS. S. STR. AND
PARAPROSOPIS (HYMENOPTERA: COLLETIDAE) Contributions in Science, No. 180.
Although it is a simple matter to separate the males of this species from
those of H. cressoni, I have found no reliable means to separate the females
of the two species. There is a difference in the overall size of the females of
these species which I have found most easily measured in terms of head width.
However, the difference is a minute one and requires precise measurements.
In figure 6A I have given the results of measurements of head width and head
length of females of H. rudbeckiae compared with females of H. cresson;
(represented by both subspecies). The range of head width is limited, varying
from 1.31 mm to 1.50 mm, with the majority of the specimens having a head
width in excess of 1.41 mm. In those specimens which have a head with less
than 1.40 mm, the head length is 1.24 mm or more. In H. cressoni the total
range of head width variation is much greater, extending from 1.12 mm to
1.37 mm. In those few specimens of H. cressoni which have a head width in
excess of 1.34 mm the head length does not exceed 1.23 mm. These differences
are slight but appear to be valid. They have been verified by checking against
associated males and in reared series.
Figure 6B contrasts the cephalic index of H. rudbeckiae with that of the
nominate form of H. cressoni. It may be noted that while both species most
frequently possess a CI rating of 92, that is, with the head a little broader than
long, a distinct tendency exists in H. rudbeckiae for the head to be broader still,
and no specimens of this species seem to have a cephalic index over 100. While
such high ratings are not common in H. cressoni, they do occur. In H. rudbeckiae,
about 70% of the females examined had a cephalic index of 92 or
less; in females of H. cressoni, only 33 % have such a low rating.
In other morphological features the females are very similar and I have
noted none that are sufficiently constant to be reliable. The two species are
almost completely sympatric, H. rudbeckiae absent only from those areas
inhabited by H. c. mesillae. In most areas H. rudbeckiae is slightly more
brightly maculate, the maculae as a rule both more extensive and of a brighter,
yellower tone. The integument of the mesoscutum and scutellum is more
densely tesselate and less shiny.
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Extracted from: Snelling R.R. (1970). Studies on North American Bees of the Genus Hylaeus, 5. The Subgenera Hylaeus, S. Str. and Paraprosopis (Hymenoptera: Colletidae). Contributions in Science No. 180, pp. 1-59
Although it is a simple matter to separate the males of this species from those of H. cressoni, I have found no reliable means to separate the females of the two species. There is a difference in the overall size of the females of these species which I have found most easily measured in terms of head width. However, the difference is a minute one and requires precise measurements. In figure 6A I have given the results of measurements of head width and head length of females of H. rudbeckiae compared with females of H. cressoni (represented by both subspecies). The range of head width is limited, varying from 1.31 mm to 1.50 mm, with the majority of the specimens having a head width in excess of 1.41 mm. In those specimens which have a head with less than 1.40 mm, the head length is 1.24 mm or more. In H. cressoni the total range of head width variation is much greater, extending from 1.12 mm to 1.37 mm. In those few specimens of H. cressoni which have a head width in excess of 1.34 mm the head length does not exceed 1.23 mm. These differences are slight but appear to be valid. They have been verified by checking against associated males and in reared series.
Figure 6B contrasts the cephalic index of H. rudbeckiae with that of the nominate form of H. cressoni. It may be noted that while both species most frequently possess a CI rating of 92, that is, with the head a little broader than long, a distinct tendency exists in H. rudbeckiae for the head to be broader still, and no specimens of this species seem to have a cephalic index over 100. While such high ratings are not common in H. cressoni, they do occur. In H. rud-beckiae, about 70% of the females examined had a cephalic index of 92 or less; in females of H. cressoni, only 33% have such a low rating.
In other morphological features the females are very similar and I have noted none that are sufficiently constant to be reliable. The two species are almost completely sympatric, H. rudbeckiae absent only from those areas inhabited by H. c. mesillae. In most areas H. rudbeckiae is slightly more brightly maculate, the maculae as a rule both more extensive and of a brighter, yellower tone. The integument of the mesoscutum and scutellum is more densely tesselate and less shiny.
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