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Extracted from: Swenk, M. H. 1915. The University Studies of the University of Nebraska, Vol. 15.
Female. Length 8–10 mm. Red; mandibles except tips, labrum, clypeus,
supraclypeus, line under eye, lateral face marks filling the space between
clypeus and orbits and extending narrowly to vertex (the mandibles,
clypeus and lateral face marks sometimes more or less suffused with red
dish), collar, tubercles, tegulae, sometimes a tiny spot on propleura, sºme
times spots on anterior and posterior corners of mesoscutum, usually spots
on lobes of mesoscutellum, large bars on each side of middle of propodeum
including enclosures, large anterior and smaller posterior spots on meso
pleura which are sometimes narrowly connected, most of front of anterior
tibiae and spots on first four coxae, all of the knees and ends of middle and usually of posterior tibiae, yellow. Ends of mandibles, spot between
bases of antennae, spot involving ocelli, posterior face of cheeks, propleura,
narrow anterior and posterior margins and broad median band on meso
scutum, depressed sides of mesoscutellum and metanotum, lower portion of
median propodeal band, metapleura and contiguous parts of propodeum,
middle coxae and posterior faces of front and hind coxae, small spots on
middle femora at base, large vaguely defined areas on posterior face of
hind femora, mesosternum and small contiguous spots on lower meso
pleura, black. Antennae red, the ends of the joints faintly dusky above,
joint 3 nearly equal 5, about two-thirds as long as 4. Wings hyaline,
darkened at ends and in marginal cell, the nervures yellow, subcostal
nervure blackish, basal nervure well basad of transverso-medial. Meso
scutellum strongly bilobed. Outer face of hind tibiae finely tuberculate.
Pubescence sparse, white or whitish, most obvious on labrum, occiput,
cheeks, mesopleura, coxae and angles of propodeum. Thorax strongly,
very densely punctured, head similarly but more finely punctured, abdomen
minutely punctured. Abdomen red, basal half of tergite I black, broad and
complete yellow bands across middle of tergites 1–4, that on I sometimes
narrowly interrupted, 5 entirely yellow, sternites 2–4 broadly yellow at
base, sternite 5 mostly yellow.
Male. Length 7.5–9 mm. In general resembles the P. Mandibles except
tips, labrum, line under and partly behind eye, clypeus, supraclypeus, lateral
face marks ending broadly at level of antennae, scape in front, collar,
tubercles, tegulae, large L-shaped spots on anterior mesopleura, oval spots
on propodeum behind and sometimes on enclosure, whole of anterior
coxae in front and spots on the other coxae, spots on first four trochanters
in front, usually small spots on first four tibial ends and often on the
knees, yellow. Area between bases of antennae extending broadly down
sides of supraclypeus and into clypeal sutures below, and coalescing broadly
with an area involving ocelli above, and cheeks behind, black. Black mark
ings of thorax as in the ‘P except that this color involves all of the median
band of the propodeum and encroaches not only over most of the sides of
the propodeum but over much of the posterior and inferior portions of the
mesopleura also, and the mesoscutum sometimes has faint lateral lines.
Mesoscutellum usually wholly red, rather feebly bilobed. Flagellum red,
largely blackened above, joint 3 less than one-half as long as 4, only slightly
over one-third as long, and distinctly shorter than 5. Abdomen colored
much as in the 2, tergites 5 and 6 yellow with an apical band or subapical
line of reddish, 7 red, deeply notched, venter red with sternite 2, and
usually 3 to 6 also, spotted or banded with yellow.
A member of the morrisoni group. Closest to N. morrisoni
Cresson FEMALE, but third antennal joint much shorter (equal to 4 in
morrisoni), mesoscutellum distinctly bilobate (slightly so in mor
risoni), basal half of tergite I black (red in morrisoni), black
median mesoscutal stripe complete, and more red on propodeum
and venter. Close also to N. dilucida Cresson FEMALE, but third
antennal joint is shorter (“a little” shorter than 4 in dilucida),
the mesoscutellum is distinctly bilobate (“slightly impressed
medially ” in dilucida), the tegulae are punctured (“smooth and
shining” in dilucida), the apical margins of tergites 1–4 are
reddish (fuscous in dilucida), the labrum, mandibles, clypeus and
supraclypeus are yellowish or yellowish red (these red in
dilucida), the mesoscutellar band is broken or lacking and the
median propodeal band is partly red. The short third antennal
joint distinguishes tricurta from N. morrisoni flagellaris Ckll.
and N. alpha Ckll. From N. maculiventer, just described, which
flies in the same locality two months later, tricurta differs at once
in the yellow instead of whitish abdominal maculations; the FEMALE is
further distinguished by the extended yellow marks on the head,
and the MALE by very decidedly longer fourth antennal joint, yellow collar and other color differences.
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