Cretolixon Lohrmann, 2020

Lohrmann, Volker, Zhang, Qi, Michalik, Peter, Blaschke, Jeremy, Müller, Patrick & Jeanneau, Laurent, 2020, † Cretolixon - a remarkable new genus of rhopalosomatid wasps (Hymenoptera: Vespoidea: Rhopalosomatidae) from chemically tested, mid-Cretaceous Burmese (Kachin) amber supports the monophyly of Rhopalosomatinae, Fossil Record 23 (2), pp. 215-236 : 223-225

Genus Cretolixon Lohrmann gen. nov.

LSID (genus): urn:lsid:zoobank.org:act:47D641BE-A9C1-4ED2-BE34-BA0D20B1766B

LSID (author): urn:lsid:zoobank.org:author:05A758C9-462A-422C-B8D6-DD9530E2BD05

Type species: Cretolixon alatum Lohrmann sp. nov.

Diagnosis

Among the rhopalosomatid genera, Cretolixon is unique in showing the following character combination: fully developed wings ( Figs. 4–7 ; Olixon spp. are brachypterous or apterous), hind wing vein M and Cu diverging far beyond cu-a ( Fig. 7 ; distad by at least the length of cu-a; in Eorhopalosoma the hind wing vein M and Cu diverge near the cross vein cu-a), occipital carina present ( Fig. 4c ; absent in Liosphex ), maxillary palpomere 3 with a distinct apical bristle ( Fig. 8b ; absent in Eorhopalosoma , Liosphex , Paniscomima , and Rhopalosoma ), labial palpomere 2 with a distinct apical bristle ( Fig. 8c ; absent in Eorhopalosoma , most Rhopalosoma , and Olixon ) each, moderately small ocelli (OOD about 3.0 times LOD; Figs. 4b , 5b , 6b ; minute in Olixon , large to very large in Eorhopalosoma , Rhopalosoma , and Paniscomima except for P. seyrigi ), and slightly concave inner eye margin ( Fig. 4b ; deeply emarginated or notched in Eorhopalosoma , Liosphex , Paniscomima , and Rhopalosoma ).

Additionally, females of Cretolixon can be easily identified by the six apical bristles on the first flagellomere ( Figs. 5b , 6e , 8a ) – the maximum number of apical bristles on flagellomere I in any other known rhopalosomatid wasp is two (as in Fig. 3a, d ).

Description

Male

Head. Labial palpus four-segmented, basal three palpomeres each distinctly shorter than fourth segment. Labial palpomere 2 with thin apical bristle, less prominent than on maxillary palpomere 3 (as in Fig. 8b, c ). Maxillary palpus six-segmented, basal three palpomeres distinctly shorter than apical three palpomeres and slightly broadening

224 V. Lohrmann et al.: † Cretolixon – a remarkable new genus of rhopalosomatid wasps towards apex. Maxillary palpomere 3 with distinct apical bristle (as in Fig. 8b, c ). Free margin of clypeus slightly concave. Ventral margin of labrum convex, obtusely angled. Mandible quadri/tridentate? (a fourth tooth may be present; however, the perspective makes a validation impossible), its apical teeth infuscate. Scapus clavate. FI conical, FII–X more or less cylindrical, FXI apically pointed. FI with two prominent apical bristles, FII–VI each with a single prominent apical bristle ( Fig. 4d ). Longer bristle on FI almost as long as flagellomere. FI shorter than FII, which is the longest flagellomere. FIII–X becoming sequentially shorter from base to apex. FXI slightly longer than FX. FI 3.0×, FII 3.3×, and FVII 2.8× as long as wide. Inner eye margin slightly concave at level of antenna (but not deeply emarginate; Fig. 4b ). Frons protruding above antennae, with two anterad projections overlapping insertion of antennae. Ocelli moderately small ( Fig. 4b ). TL 2.0×, OOD 3.0×, MOD 1.0× LOD. Ocellar triangle infuscate ( Fig. 4b ). Occipital carina present ( Fig. 4c ). Occiput concave ( Fig. 4c ).

Mesosoma. Pronotum rather long, anterad strongly narrowing in dorsal view, dorsal posterior margin strongly concave. Notaulus apparently absent. Parapsidal sulcus straight, slightly longer than half of mesoscutal length, reaching posterior mesoscutal margin. Mesosternal lobes present, separated from mesosternum by slight depression (but not constricted as in Paniscomima and Rhopalosoma ). Metapleuralpropodeal suture carinate ( Fig. 4c ). Propodeum with median slightly longitudinal tubercle on anterior section. Dorsal face of propodeum in lateral view convexly rounded.

Legs. Fore leg with one tibial spur. Middle and hind legs with two tibial spurs each, inner spur of hind leg modified as calcar. Tarsomeres I–IV each with plantar lobe. Pretarsal claws bifid. Arolium present.

Fore wing. With eight enclosed cells: C, R, 1Cu, 1R1, 2R1, 1Rs, 1M, and 2Cu ( Figs. 4e , 7 ). Costal cell very narrow, over complete distance narrower than bordering veins. Pterostigma narrow. Cell 2R1 (marginal cell) short, ending well before apex of wing. Base of vein M + Cu neither tubular nor present as remnant. Vein cu-a slightly curved, distad of M 1 by 1.0× length of cu-a. Vein M 1 curved, intersecting vein Cu at an angle of almost 90 ◦. Vein 1m-cu straight. Faint remnant of vein 2m-cu received by distal section of second submarginal cell (1Rs). Vein Rs 1 almost straight, about 1.7× length of M 2. Cell 1Rs 2.1× as long as high. Vein CuA distinct, CuP barely present but very short and inconspicuous. Anal lobe without adventitious vein. Wing membrane covered and ventral margin fringed with short, evenly distributed setae.

Hind wing. With two complete cells: R and Cu ( Fig. 7 ). Costal cell only present as membranous area anterior to Sc + R, not enclosed by C. Jugal lobe absent. Anal vein tubular and pigmented, ending at cu-a. Sc + R tubular and pigmented, at basal two-thirds fused with C. Vein R tubular not reaching further than distal hamuli. Vein Rs tubular, straight and slightly reclivous at basal section (Rs ∗), distal section not tubular but weakly pigmented; pigmentation distally fading. Vein M + Cu tubular and slightly pigmented. Vein Cu not tubular but markedly pigmented, not reaching distal half of wing membrane. Vein M basally tubular but not pigmented, diverging from vein M + Cu by its length beyond cu-a, ending even before connecting with r-m. Vein cu- a oblique, tubular but not pigmented. Five to six basal hamuli straight, their length continuously increasing distad. Five to six distal hamuli. Distal hamuli curved, hook-shaped; similar in size and form. Wing membrane covered and ventral margin fringed with short, evenly distributed setae.

Metasoma. Segment I less than 1.5× as long as wide. Posterior half of tergite I with median depression broadening posterad. Cercus paddle-shaped and with apical setae. Parameres spine-like, upcurved.

Pilosity. Body completely covered with fine pubescence. Pubescence on metasoma slightly longer than on rest of body.

Female

Head, mesosoma, and metasoma as in male except the following: maxillary palpomeres 2 and 3 each with apical stiff bristle. FI very short, about same length as pedicel and onefifth the length of FII. FI 1.1×, FII 3.9×, and FVII 2.9× as long as wide. FI with six prominent apical bristles along inner margin ( Figs. 5b , 6e , 8a ), longest bristle (on dorsal side) almost as long as FII, shortest bristle (on ventral side) only as long as FI. FII and FIII with a single prominent apical bristle. TL 2.0×, OOD 2.5×, MOD 1.1× LOD. Fore wing vein Rs 1 about 1.6× length of M 2. Hind wing with six basal and six distal hamuli. All legs with tarsomere I cylindrical, tarsomeres II–IV dorsoventrally flattened, laterally widened, and distally slightly broadening. Distal margin of tarsomere IV bilobed ( Fig. 5d ). Tarsomeres ventrally with dense short erect setae. Tarsomeres without plantar lobes and tarsal fenestrae. Tarsomeres I–III with apicolateral bristles. Pretarsal claws simple, without preapical teeth. Arolium large. Sting upcurved.

Etymology

The new genus group name is a combination of “ cret -” (referring to Cretaceous) and the name of the recent genus Olixon . The name is neuter.

Figures

Figure 3. Some diagnostic characters of Rhopalosomatidae. (a) Liosphex bribri Lohrmann (in Lohrmann and Ohl, 2010), female, paratype, apical bristles on basal flagellomeres. (b) Paniscomima kilombero Lohrmann, 2011, female, paratype, last metasomal segments with upcurved sting. (c) Liosphex varius Townes, 1977, male, mesosternal lobes covering the bases of the mesocoxae. (d) Olixon ferrugineum Krogmann et al., 2009, female, paratype, apical bristles on basal flagellomeres. (e) Rhopalosoma poeyi Cresson, 1865, male, last metasomal segments with upcurved parameres. (f) Fourth instar larva of a rhopalosomatid (Olixon?) wasp on a nemobiine cricket (Nemobiinae), collected in Florida, USA (deposited in the personal collection of Volker Lohrmann). Abbreviations: ab – apical bristle; FI, FII, FIII – flagellomere 1, flagellomere 2, flagellomere 3; T5, T6, T7 – metasomal tergite 5, metasomal tergite 6, metasomal tergite 7; msl – mesosternal lobe; msc – mesocoxa; mtc – metacoxa; pa – paramere. A cutout of panel (f) was first published in Fossil Record (Lohrmann and Engel, 2017).

Figure 4. Cretolixon alatum gen. et sp. nov., male, holotype (MB.I 6500; ZMB). (a) Habitus in lateral view. (b) Head in slightly oblique frontal view.(c) Mesosoma in lateral view.(d) Partial right antenna.(e) Wings.Abbreviations:ab – apical bristle; FI, FII, FIII – flagellomere 1, flagellomere 2, flagellomere 3; lo – lateral ocellus; oc – occipital carina; p – pedicel; sc – scape. The arrowheads indicate the apical bristles on third maxillary palpomeres (c) and basal flagellomeres (d).

Figure 5. Cretolixon alatum gen. et sp. nov., female, paratype (VL-Bu-04, UMB). (a) Habitus in lateral view. (b) Head and basal halves of antennae in oblique lateral view. (c) Mesosoma in lateral view. (d) Right protibia and protarsus. (e) Wings. The arrowheads indicate the apical bristles on second labial and third maxillary palpomeres (b).

Figure 6. Cretolixon alatum gen. et sp. nov., male and female, paratypes (male: SNSB-BSPG 2020 XCIII 25, SNSB; female: NIGP173865, NIGP). (a, c, d) Male. (a) Habitus in lateral view. (c) Base of right antenna. (d) Base of left antenna. (b, e) Female. (b) Habitus in slightly oblique dorsal view. (e) Partial right antenna (apex of FI to base of FIV). The arrowheads indicate the apical bristles on basal flagellomeres.

Figure 7. Cretolixon alatum gen. et sp. nov., male, holotype (MB.I 6500; ZMB). Venation of fore and hind wings (microtrichia omitted, drawing based on a photograph with a perspective similar to that of Fig. 4e).

Figure 8. Cretolixon alatum gen. et sp. nov., female, paratype (VL-Bu-04; UMB). (a) Basal half of left antenna. (b) Details of mouth parts (maxillary palpus highlighted in grey). (c) Details of mouth parts (labial palpus highlighted in grey). Abbreviations: FI, FII, FIII – flagellomere 1, flagellomere 2, flagellomere 3; G – gena; lp1,..., lp4 – labial palpomere 1,..., labial palpomere 4; M – mandible; mp2,..., mp6 – maxillary palpomere 2,..., maxillary palpomere 6; p – pedicel; sc – scape. Drawings based on Fig. 5b.