Thyreomelikertes electrosinicus, Engel & Xie, 2024

Thyreomelikertes electrosinicus , new species

Figures 20–25 View FIGURE 20 View FIGURE 21 View FIGURE 22 View FIGURE 23 View FIGURE 24 View FIGURE 25

DIAGNOSIS: This species differs from its only congener (see below for alternative character states) in the that the metatibial fringe, fundal, and corbicular setae are as long as than the maximum width of the metatibia (figs. 20, 21, 25), and similarly, the setae of mesotibia are about as long as the maximum mesotibial width and are intermixed with capitate setae (fig. 24). The species is also larger, with a forewing length over 5 mm. It also seems that the facial setae are sparser than those of the other species (fig. 22).

DESCRIPTION: WORKER. Total body length (as preserved) 5.44 mm; forewing length (as preserved) 5.30 mm. Head slightly longer than wide, length (summit of vertex to clypeal apical margin) 1.47 mm, width (maximum width across compound eyes, eyes partially collapsed inward thereby shortening the value) 1.29 mm; upper interorbital distance 1.26 mm, lower interorbital distance 1.22 mm. Scape elongate, length 0.58 mm, longer than torulocellar distance; flagellomere I longer than flagellomere II, about as long as combined lengths of flagellomeres II and III, flagellomere II shorter than flagellomere III. Gena distinctly narrower than compound eye in profile. Pronotum short, declivitous; mesoscutum anterior border broadly rounded, anterior lip gently curving to meet posterior pronotal margin; mesoscutum medial length 1.04 mm; intertegular distance 1.07 mm; mesoscutellum medial length 0.39 mm. Metatibia slender, length 2.09 mm, maximum width 0.41 mm; metabasitarsus longer than wide, length 0.81 mm, maximum width 0.34 mm, apical margin comparatively straight. Forewing with basal vein (1M) straight, confluent with 1cu-a, pterostigma longer than wide, maximum width slightly proximal to midlength, margin inside marginal cell sloping to costal margin; marginal cell broadly rounded apically, well separated from anterior wing margin; 2Rs arched posteriorly; 3Rs shorter than r-rs and slightly shorter than 4Rs; 1rs-m straight, 2rs-m strongly arched apically in posterior half; 2m-cu proximal 2rs-m by about vein width; wing membranes hyaline clear; veins dark brown.

Labrum faintly imbricate and impunctate; clypeus seemingly smooth with some weak, shallow punctures laterally; integument of much of face difficult to discern owing to collapse of face, but vertex smooth and shining, seemingly impunctate. Mesoscutum and mesoscutellum apparently smooth with sparse faint punctures (integument exceptionally challenging to observe); metasomal terga smooth to faintly imbricate and shining, with minute punctures at bases of setae.

Pubescence generally fuscous and rather abundant; labrum with sparse, erect, simple setae on surface, apical margin with fringe of elongate setae, such setae about 0.75× labral length; clypeus with scattered, simple, erect, short setae, such setae more numerous on remainder of head and becoming quite elongate on vertex. Scape with scattered short, erect to decumbent, simple, fine setae, without bristles. Mesosoma rather densely pubescent but not obscuring integument, setae elongate, erect, and simple or with minute branches along rachis, many setae noticeably thick on all surfaces except metanotum and basal area of propodeum; plumose setae more numerous on posterior of mesoscutellum, with branches slightly longer and more numerous, thus appearing brushy. Wing membranes with abundant microtrichia. Profemur and protibia with abundant, short setae, those of dorsal surfaces longer than those of prolateral, retrolateral, and ventral surfaces; probasitarsus with long, erect bristles on dorsal surface, similar bristles on other surfaces except slightly shorter; mesofemur with abundant short, erect setae, intermixed with short bristles on outer surface, ventrally setae shorter and bristles lacking; mesotibia with dense, erect setae and bristles, on dorsal surface, such setae and bristles progressively longer from base to near apex, setae with some minute branches, retrolateral surface with bristles sparse and setae longer, about as long as mesotibial width, such setae with abundant minute branches and some with thickened apices, thus appearing somewhat clavate apically, ventral surface with setae shorter; mesobasitarsus similar to mesotibia except bristles longer and more numerous on dorsal surface and more evident on retrolateral surface, setae of retrolateral surface not appear clavate; metafemur with short, erect setae on dorsal and prolateral surfaces, retrolateral and ventral surfaces with setae exceedingly sparse, with a patch of keirotrichia on retrolateral surface apically; metatibia with abundant, long, erect bristles along anterior edge of proventral surface and inferiorly on prolateral surface, such setae intermixed with long, minutely branched setae, proventral surface largely asetose, prolateral surface with sparsely scattered long, erect, simple setae and bristles, such setae similar on profundal and corbicular surfaces, retromarginal fringe composed of dense, long, minutely branched setae, such setae about as long as maximum metatibial width, retrolateral surface with keirotrichiate zone covering majority of surface except narrow, slightly depressed, superior, subglabrate zone and squarish, apical subglabrate zone; rastellum composed of dense series of thick bristles tapering in length; metabasitarsus with abundant erect bristles on proventral and prolateral surfaces, bristles intermixed with some short setae, retromarginal edge with bristles less prominent, with dense minutely branched setae, such setae slightly shorter than bristles and rounding onto superior apical angle, retrolateral surface with loose comb rows composed of long, suberect bristles; auricle bordered by fringe of short, branched setae. Metasomal setation as described for genus (above).

QUEEN AND MALE. Unknown.

HOLOTYPE: Female worker, CNU-HYM- LF-2023-001 (figs. 20, 21), in a single piece of amber without syninclusions, Fushun coalfield, Liaoning Province, northeastern China, Guchengzi Formation , Ypresian (Eocene); deposited in the fossil insect collection of the Key Laboratory of Insect Evolution and Environmental Changes , College of Life Sciences, Capital Normal University, Beijing, China.

The holotype is the best preserved of the available bees from Fushun amber and is virtually complete, and observation is not hampered by prominent syninclusions, bubbles, or other imperfections in the amber. The bee is rather close to some curved surfaces that prevent preparation of the amber surface from some angles— the only hindrance to a perfect view of certain features. The wings are extended posteriorly over the body, although the left forewing is slightly more askew. The forelegs are raised near the head, although the left foreleg is more extended into the amber beneath the bee. The mid and hind legs are extended below and, with the exception of the left midleg, project out from the body. The worst defects concern the head, which is somewhat obscured by an oblique internal fracture. More critically, the integument of the face is partially collapsed, rendering interpretation a challenge. The top of the head and the mesosomal nota are partially obscured by encrusted material entangled in the setae, somewhat obscuring the integument. The mesosoma and metasoma are partially compressed but inconsequentially. The wings are excellent although the left forewing was slightly stretched during preservation, resulting in slight fractures along some of the fenestrae, bullae, and across the marginal cell. The right forewing is unmolested.

ETYMOLOGY: The specific epithet is a combination of the Latin adjective electricus (from electrum), meaning, “of amber” and the Medieval Latin adjective sinicus, meaning “of or related to China.”