Brevivulva electroma Gibson, 2009

Gibson, Gary, 2009, Description of three new genera and four new species of Neanastatinae (Hymenoptera, Eupelmidae) from Baltic amber, with discussion of their relationships to extant taxa, ZooKeys 20 (20), pp. 175-214 : 190-194

Brevivulva electroma Gibson , sp. n.

urn:lsid:zoobank.org:act:594F760F-5932-4157-BDA2-1D5CE50E1500

Figs 33–44

Etymology. The generic name is formed from the Latin words brevis, meaning “short”, and vulva, meaning “cover” or “wrapper”, in reference to the short hypopygium compared to Lambdobregma . The species name is formed from the Latin word electrum, meaning “amber”.

Type material. Holotype (Figs 33–35): ♀, AMNH, labelled “ AMNH BaJWJ-408” / “ HOLOTYPE Brevivulva electroma Gibson ”. The unique female is near one end of a piece of Baltic amber that is triangular in cross section and about 21 mm long and 5 mm wide when it is faced dorsally. The specimen is complete but a white milky substance obscures the right half of the lower face and mouthparts (Figs 37, 38), and the ventral surface of the gaster beyond the hypopygium (Fig. 34).

Description. Length = 3.25 mm, including ovipositor sheaths. Body dark with faint metallic green luster on mesosoma under some angles of light. Head in frontolateral view (Fig. 37) with convex interantennal region separating ventrally distinct scrobes, dorsally continuous scrobal depression shallowed dorsally and smoothly merged with frons below ocelli; face uniformly coriaceous and setose except scrobes bare; parascrobal region incurved slightly and ridged from beside torulus to level about equal with dorsal angle of interantennal region (Fig. 38). Head in lateral view with

Figures 33–38. Brevivulva electroma sp. n. (♀ holotype): 33 dorsal habitus 34 ventral habitus 35 ventrolateral habitus 36 dorsal head 37 frontolateral head 38 frontal head.

length of gena posterior to eye subequal to malar space. Head in dorsal view (Fig. 36) with vertex and temple rounded into occiput; about 1.6× as wide as long; distance between eyes about 0.3× head width; maximum diameter of ovoid posterior ocellus about 2.5× OOL and 0.5× POL; occiput without occipital carina. Eye at least superficially bare (Figs 36–38). Antenna (Figs 37, 38) 13-segmented with ratio of segments = 12.5: 5.2: 2.2: 4.5: 3.2: 3.2: 3.2: 3.0: 2.8: 2.6: 5.2; scape narrow and cylindrical basally, but about apical two-thirds widened; funicle with 8 segments, fu 1 about 1.5× longer than wide, fu 2 the longest segment and subsequent funicular segments increasingly shorter and wider; clava compact 3-segmented with sutures almost straight transverse and with only small micropilose sensory region ventroapically (Fig. 37: mps). Pronotum in dorsal view (Figs 33, 39: no 1) about half length of mesoscutum, sides anteriorly convergent and posterior dorsal margin slightly incurved; dorsal surface slightly convex, finely mesh-like coriaceous-reticulate. Tegula elongate-triangular with almost truncate posterior margin. Mesoscutum (Fig. 39) not shoulder-like posterior to pronotum, as long as greatest width, and with posteriorly ridge-like, parallel parapsidal lines (Fig. 39: psr) differentiating slightly concave, elongate-rectangular median region from inclined lateral regions; sparsely and inconspicuously setose; median mesoscutal region with larger and more distinct mesh-like reticulation than on pronotum, lateral mesoscutal regions with sculpture similar to median region but apparently shallower, more coriaceous toward lateral margin, and parapsidal lines with much smaller and finer coriaceous sculpture. Scutellar-axillar complex with distinct, longitudinally crenulate scutoscutellar sutures (Figs 39, 40: sss) differentiating convex axillae and scutellum; axillae equilateral-triangular with contiguous inner angles, with finer coriaceous sculpture compared to mesoscutum, and without distinct setae; scutellum not laterally carinate, coriaceous-imbricate anteriorly to meshlike-reticulate posteriorly and apparently quite uniformly and sparsely setose, protuberant posteromedially, the protuberance (Fig. 40: scp) projecting ventrally into medial depression of metanotum. Metanotum (Figs 39, 40: no 3) strongly transverse, slender, with posterior margin almost straighttransverse and with anterior margin U- like reflexed under scutellar protuberance so as to apparently form concave, cup-like region having a vertical posterior surface. Propodeum in dorsal view (Figs 40, 41) very short; plical region strongly transverse with shallowly incurved foramen (Fig. 40: pfr) and apparently slightly concave medially under scutellar-metanotal protuberance; spiracle near midlength laterally. Prepectus (Figs 35, 41: pre) conspicuously elongate-triangular, the apical half abruptly narrowed and tapered to acute angle. Mesopleuron (Fig. 41) with uniformly convex acropleuron extending posteriorly to region between bases of meso- and metacoxae, with linear acropleural sulcus (Fig. 41: acs) extending forward from mesocoxa to level about equal with base of tegula where abruptly recurved dorsally as obscure arcuate line extending to prepectus near apical third; acropleuron bare, mesh-like reticulate anteriorly to more finely coriaceous posteriorly, the sculpture elongated and more or less aligned in rows posteriorly; mesepisternum sparsely setose anterior to arcuate portion of acropleural sulcus and ventral to horizontal portion of sulcus (Fig. 41: mes) except for bare, triangular remnant of mesepimeron (Fig. 41: lep) between acropleuron and mesosternum. Metapleuron uniformly setose, strongly tapered ventrally so as to extend as almost linear strip (Fig. 41: pl 3) between acropleuron and metacoxa to base of mesocoxa. Mesosternum (Fig. 34) with deep sulcate discrimen, without transepisternal sulcus, and with straight-transverse posterior margin abutting mesocoxae. Protibia apparently with apical spicule. Middle leg conspicuously long (Figs 33–35), about as long as body and longer than hind leg; mesocoxa with large basolateral cavity opposite angle formed between acropleuron and mesepisternum (Fig. 41: mcc); mesotibia with row of dark, variably long spines along apical margin (Fig. 43: map) and with mesotibial spur about 3x as long as apical width of tibia; mesotarsus (Fig.43) slender with subcylindrical seg-

Figures 39–44. Brevivulva electroma sp. n. (♀ holotype): 39 dorsal mesosoma 40 scutellar axillar complex to base of gaster 4Ι mesosoma, ventrolateral view 42 middle part of fore wing 43 mesotarsus and tibial spur 44 posterior of gaster, lateral view.

ments, the basal four segments with even row of short pegs along at least anterior ventral margin and apical peg on slightly higher plane than others (i.e., also on apical margin of respective segment). Hind leg with tibia and tarsus slender, subcylindrical, and apparently without black, peg-like spines along apical margin exterior to outer spur. Fore wing hyaline (Figs 33, 42); costal cell extensively setose along leading margin; basal cell and disc uniformly setose except for linea calva (Fig. 42: lc) behind parastigma, anterior margin of bare band delimited by slightly thicker microtrichia; cubital and vannal areas apparently bare; cc: mv: pmv: stv = 5.5: 2.7: 3.1: 0.9; stigmal vein with distinct uncus. Gaster very broadly sessile, with at least seven uniformly setose gastral tergites; cercus (Fig. 44: cer) at extreme posterior margin of terminal segment; terminal segment with transverse suture (Fig. 44: sut) anterior to cercus delimiting apparently fused Gt 7 and Gt 8, the presumptive Gt 8 comprising about apical quarter of syntergum and length of syntergum about 0.6× length of Gt 6; hypopygium extending about half length of gaster (Fig. 35: hyp). Ovipositor sheaths (Fig. 44: ovs) projecting by slightly less than half length of gaster, tapered and slightly curved down apically.

Biology. Unknown, but the exerted, stiff ovipositor sheaths suggest the species was a parasitoid of wood-boring beetles or other hosts in concealed situations.

Remarks. Brevivulva electroma closely resembles species classified in the extant genus Lambdobregma , including having a conspicuously elongate-triangular prepectus that narrows abruptly posteriorly (Figs 35, 41: pre; Gibson 1989, fig. 40). It keys readily to Lambdobregma using Gibson (1989) except for the absence of transepisternal sulci, but differs also by having posteriorly carinate, ridged parapsidal lines (Fig. 39: psr), the hypopygium extending only about half the length of the gaster (Fig. 35: hyp) rather than almost to its apex, Gt 6 not concealing the syntergum, and the cercus at the extreme posterior margin of the syntergum (Fig. 44: cer). It also differs in having what appear to be slightly less derived relative structures of two features. Species of Lambdobregma have a conspicuously elongate-slender acropleuron (Fig. 21) that extends to the base of the metacoxa so that in lateral view the acropleuron conceals the linear, bare, ventral extension of the metapleuron (Fig. 16), whereas in B. electroma a setose ventral strip of the metapleuron remains between the acropleuron and metacoxa (Fig. 41: pl 3) because the acropleuron is slightly less elongate. The scutellum is also posteromedially protuberant in both B. electroma and Lambdobregma , but in Lambdobregma it extends as a hook-like process over the metanotum into a depression of the propodeum (Figs 15, 16). In B. electroma the scutellar protrusion only extends into a medially concave portion of the metanotum (Fig. 40: scp, no 3). Head structure of B. electroma resembles that of the undescribed species of Lambdobregma from Chile because both have a Λ- shaped scrobal depression (Figs 37, 38), whereas other Lambdobregma have a subdivided scrobal depression ( Gibson 1989, fig. 15). The Chilean species also lacks setae from the propodeal plical region similar to B. electroma , but apparent absence from B. electroma may be an artifact of preservation.

The features discussed above suggest B. electroma could be the sister species of the Chilean species + other extant Lambdobregma , but absence of parapsidal lines and relative scutellar-metanotal-propodeal structure could also support it as the sis- ter group of Lambdobregma + Neanastatus (see Discussion). Because of the uncertain relationships of B. electroma and because it is differentiated from extant Lambdobregma by several features I prefer to establish a new genus for it rather than expanding the generic limits of Lambdobregma .