Leptoomus janzeni, Gibson, Gary A. P., 2008

Gibson, Gary A. P., 2008, Description of Leptoomus janzeni, n. gen. and n. sp. (Hymenoptera: Chalcidoidea) from Baltic amber, and discussion of its relationships and classification relative to Eupelmidae, Tanaostigmatidae and Encyrtidae, Zootaxa 1730, pp. 1-26 : 2-8

Leptoomus janzeni , n. sp.

( Figs 1–19, 21 )

Type material. Holotype (female, AMNH BaJWJ-400): near the end of a somewhat wedge-shaped block of clear, yellowish Baltic amber of unknown origin. The block is about 12 mm in length and is enlarged toward the end with the specimen. The specimen is complete except that the right leg projects out of one side of the block so that the mesotarsus lacks the apical four tarsomeres. A thin sliver of amber is also missing from the block next to the frontal surface of the head so that the right antenna is missing beyond the third flagellar segment, but an impression of the flagellum remains in the amber ( Fig. 3 ); internally a crack from the damaged area extends on the right side of the specimen to about the posterior margin of the prepectus. The wings are flat over the body ( Fig. 1 ) so that the propodeum and metasoma are not visible from dorsal view and because of the shape of the block the body is not clearly visible from a direct ventral view.

Paratypes: 4 females ( AMNH BaJWJ-401−404), 2 males ( AMNH BaJWJ-405 and 406) in separate amber pieces.

Etymology. The genus name is formed from the Greek words leptos, meaning “thin” or “small” and omos, meaning “shoulder”, in reference to the structure of the prepectus. The species name is in honour of Jens-Wilhem Janzen, who acquired the type series as part of his long interest in Baltic amber.

Description. Body length 2.4–2.75 mm. Head and body dark brown, but appearing silvery where surrounded by thin layer of air (e.g., Figs 4 , 13, 16 ).

Head. In frontal view ( Fig. 3 ) broadly rounded, slightly wider than high, not vaulted above eyes; reticulate to coriaceous-reticulate ventrally and uniformly setose except scrobal depression bare. Clypeus delimited laterally by small anterior tentorial pit near oral margin at level of inner margin of torulus ( Fig. 3 : atp), smooth, shiny, and bare except for 2 long setae laterally, one more basal than other; apical margin straight-transverse ( Fig. 3 ). Scrobal depression comparatively broad, distinct but smoothly merged with parascrobal region and vertex, and scrobes separated ventrally by convex, dorsally tapered interantennal region ( Figs 3, 5 ). Toruli distinctly below lower margin of eyes ( Figs 3, 5 ); distance between toruli equal to distance between lower margin of torulus and oral margin, about 1.25 times width of torulus, and about 0.5 length of malar space. Malar space with complete malar sulcus ( Figs 3, 5 , 10 ). Eye with very short, inconspicuous, sparse microtrichia; in dorsal view ( Figs 1, 2 ) minimum distance between eyes about 5–6 times diameter of anterior ocellus and about 0.36 times head width. OOL slightly greater to slightly less than diameter of posterior ocellar diameter ( Figs 1, 7 ); OOL:POL:LOL about 1:3:2.5 ( Figs 1, 2 ). Mandible with acute ventral tooth and very slightly concave dorsal truncation ( Fig. 3 , cf. Tachikawa 1973, fig. 2C). Antenna ( Figs 3, 5 ) 12-segmented (1:1:7:3); scape compressed but thick, length excluding radicle about 4 times maximum width; funicle with all segments slightly transverse to subquadrate, the basal segment not distinctly ringlike or conspicuously differentiated from subsequent segments; clava compact, about as long as combined length of apical 3 funicular segments, subdivided by fine sutures and in lateral view with apex strongly, obliquely truncate ( Fig. 5 ), the truncate region consisting of oval micropilose sensory region ( Fig. 3 ).

Mesosoma. Pronotum in dorsal view ( Figs 4, 7, 8 ) with short, coriaceous-reticulate collar, anteriorly the collar evenly rounded into vertical surface without distinct neck and laterally extending to mesothoracic spiracle and inner margin of prepectus, with dorsolateral margin obliquely angled relative to concave posterodorsal margin so as to form a short, posteriorly projecting lobe overlaying shallow anterolateral depression of mesoscutum (cf. Figs 4, 6, 8 ); in lateral view posterior margin of pronotum arcuate so as to partly surround anterior margin of prepectus ( Figs 10–13 ), but usually with narrow inflexed band ( Figs 3 , 10–12 : ppi) abutting anteroventral margin of prepectus (one female with normally inflexed portion extending posteriorly exterior to prepectus as flat, lobelike surface, Fig. 13 : ppi). Prepectus visible in dorsal view ( Fig. 4 ), moderately thick rather than flaplike, but appressed to mesoscutum and not conspicuously protuberant; in lateral view ( Figs 10– 13 ) comprising about one-third combined length of prepectus and acropleuron, isodiametric-coriaceous, with posterior margin at almost right angle to dorsal margin ( Fig. 11 ) and appressed to acropleuron, and with anterior angle rounded and projecting under spiracle very slightly anterior to level of spiracle ( Figs 11–13 : sp1); in ventral view ( Fig. 3 : pp) keel-like, with inner and outer surfaces forming a pouch external to ventrolateral margin of pronotum ( Fig. 3 : ppi) and projecting conspicuously beyond anterior margin of mesosternum ( Figs 5 , 10 : ams) so sternum and prepectus form a deep U-shape when prothorax slightly displaced from sternum ( Figs 5 , 10 ). Mesonotum, when not flexed, with posterior margin of mesoscutum overlapping anterior margin of scutellar-axillar complex slightly so as to separate inner angles of axillae mesally ( Figs 1, 4, 7 : arrows), but when flexed with mesoscutum and scutellar-axillar complex separated by linear membranous band and inner angles of axillae contiguous ( Fig. 8 : arrow). Mesoscutum quadrangular, wider than long ( Figs 1, 2, 4, 8 ) except in BaJWJ-403 ( Fig. 7 ) (probably an artefact of preservation), reticulate, uniformly setose and without evident parapsidal lines or linear notauli, but with shallow longitudinal depression extending between posteriorly projecting lobe of pronotum and lateral margin of axilla (cf. Figs 6, 7 : not); posterior margin almost straight-transverse, curved slightly posteriorly when mesonotum unflexed ( Figs 4, 7 ) and slightly emarginate when mesonotum flexed ( Fig. 8 ); scutellar-axillar complex similarly sculptured and setose as mesoscutum; axillae transverse-triangular with dorsal surface in same plane as scutellum and distinguished from scutellum by very shallow, linear furrow ( Figs 4, 6–8 ). Acropleuron ( Figs 10, 11, 13 ) convexly enlarged, extending posteriorly to metacoxa between metapleuron and mesocoxa, but separated from base of mesocoxa by slender, ventral portion of mesepimeron ( Fig. 14 : epm); acropleural sulcus horizontal, extending straight forward to near posteroventral angle of prepectus where arched dorsally as more obscure, obliquely angled furrow ( Figs 10, 11 : acs); finely, obliquely strigose-coriaceous over about anterior half, but minutely netlike coriaceous mesally and shiny and almost smooth posteriorly. Mesosternum quadrangular, without distinct discrimen but apparently slightly convex on either side of mediolongitudinal furrow; posterior margin differentiated as slen- der rim ( Figs 10, 13, 15 : msr) posterior to mesofurcal pit ( Figs 10, 14, 15 : mfp), the margin straight-transverse but separated from each mesocoxa by wide membranous region ( Figs 9, 14 : mb) along anterior margin of coxa lateral to basomedial lobe. Mesotrochantinal plate ( Figs 14, 15 : mtp) inflected internally at abrupt angle to mesosternum, comparatively narrow mesally in region under basomedial lobes of mesocoxae ( Fig. 15 : bml), but laterally with slender, transverse region between posterior margin of mesosternum and membranous region anterior to each coxa ( Figs 14, 15 : mb). Metanotum not clearly visible in any specimen, but apparently bandlike below scutellum ( Gibson 1989, cf. fig. 49); metapleuron ( Fig. 11 : pl3) triangular, very finely isodiametric coriaceous and appearing bare in most specimens but with 2 setae above carinate ventral margin in BaJWJ-402. Propodeum not clearly visible in any specimen but transverse without distinctly differentiated plical and callar regions, surface low convex with linear postspiracular sulcus; possibly with short median carina, but at least with large spiracle within anterior half ( Fig. 11 : sp2), and setose lateral to spiracle.

Appendages. Fore wing ( Figs 1, 2 , 16 ) hyaline; marginal and stigmal veins separated by distinct though short hyaline break and stigmal vein with distinct uncus ( Fig. 16 ); female with mv about 1.3–1.4x length of stv, 1.0–1.2x length of pmv, and 0.3–0.4x length of smv (n=3), and male with mv about 1.2x length of stv, 0.85x length of pmv, and 0.3x length of smv (n=1); basal and mediocubital folds setose and basal cell almost completely setose except narrowly along mediocubital fold; disc with broad speculum ( Fig. 16 : spc) contiguous with parastigma extending between basal fold and base of marginal vein (cf. Tachikawa 1973, fig. 2A). Mesocoxa in lateral view ( Figs 10, 11, 13 ) inserted ventral to metacoxa near posterior margin of acropleuron, lateral surface with oblique ridge extending between posteroventral and anterodorsal angles, the surface concave ventral to, and convex dorsal to ridge such that concave region narrowed toward base. Metacoxa in lateral view about twice as high as wide and almost vertical, inserted high on mesosoma with broad, almost vertical anterodorsal attachment ( Fig. 11 ). Protibia with curved, apically bifurcate tibial spur ( Fig. 21 : pts); inner apical margin with secondary fine comb ( Fig. 21 : sec) consisting of about 6 flattened setae in oblique row; inner dorsoapical margin above secondary fine comb with peglike (female, Fig. 21 : pas) or more spinelike (male, Fig. 21 insert: pas), apparently articulated spicule; outer surface with 2 strong spines subapically, at least in female ( Fig. 21 : pls). Mesotibia with about 12 short pegs (female, Fig. 19 insert: map) or spines (male, Fig. 18 ) arranged in 1 or 2 irregular rows along inner apical margin and with strong, microsetose tibial spur extending for distance about equal to length of basitarsus ( Fig. 19 ); metatibia with two spinelike tibial spurs. Tarsi 5-segmented ( Fig. 19 ); female mesotarsus with straight line of peglike setae along anterior and posterior ventral margins of basal 4 tarsomeres, distally the pegs not extending along anteroapical margin of each tarsomere, and at least basitarsus appearing to have more pegs along anterior than posterior margin ( Fig. 19 ); male mesotarsus with more spinelike setae ventrally ( Fig. 18 ).

Metasoma. Metasoma of female with 8 tergites and with small anal plate ( Fig. 17 : anp) over ovipositor sheaths; broadly sessile with Mt1 (petiole) transverse, striplike; Mt2-Mt7 of similar length, transverse-rectangular, finely coriaceous with transverse rows of setae ( Fig. 9 ); Mt7 with spiracle ( Fig. 17 : sp3); Mt8 (syntergum) short dorsally, setose, with dorsal surface ( Fig. 17 : Mt8) differentiated from outer plate of ovipositor ( Fig. 17 : opo) by longitudinal groove ( Fig. 17 : grv) posterior to cercus ( Fig. 17 : cer). Cercus at anterolateral angle of Mt8 but not conspicuously advanced, with 2 short and 2 long setae, the setae not kinked. Hypopygium extending about half length of gaster. Ovipositor sheaths protruding only slightly beyond apex of metasoma ( Fig. 17 ).

Figures

FIGURES 1 – 8. Leptoomus janzeni. 1 and 2, habitus dorsal: 1, Ψ holotype; 2, ♂ 405. 3, head, antenna and prepectus (holotype). 4, mesonotum dorsal (Ψ 401). 5, head, antenna and prepectus (Ψ 401). 6 – 10, mesonotum: 6, dorsolateral (Ψ 402); 7, dorsal (Ψ 404); 8, dorsal (♂ 405) [arrows point to inner angle of axillae on Figs 1, 4, 7, 8].

FIGURES 9 – 16. Leptoomus janzeni. 9, habitus lateral (holotype). 10 and 11, mesosoma lateral: 10, ♂ 406; 11, Ψ 401. 12, pronotum-prepectus lateral (Ψ 402). 13, mesosoma lateral (Ψ 404). 14 and 15, mesocoxal articulation: 14, ventrolateral (holotype); 15, posteroventral (Ψ 402). 16, fore wings (Ψ 401).

FIGURES 17 – 26. 17 – 19, Leptoomus janzeni: 17, apex of gaster (Ψ 402); 18, mesotarsus and apex of mesotibia (♂ 406); 19, mesotarsus [lines indicate separation between tarsomeres] and [insert] mesotibial apical pegs (holotype). 20, Cynipencyrtus flavus, apex of pedicel to fourth funicular segment. 21 – 26, apex of protibia: 21, L. janzeni (Ψ 401) and [insert: ♂ 406]; 22, Eopelma n. sp.; 23, Lambdobregma n. sp.; 24, C. flavus; 25, Tanaoneura hirticoxa LaSalle; 26, Aenasius sp.