Proneuronema gradatum, Makarkin, Vladimir N., Wedmann, Sonja & Weiterschan, Thomas, 2016

Makarkin, Vladimir N., Wedmann, Sonja & Weiterschan, Thomas, 2016, A new genus of Hemerobiidae (Neuroptera) from Baltic amber, with a critical review of the Cenozoic Megalomus - like taxa and remarks on the wing venation variability of the family, Zootaxa 4179 (3), pp. 345-370 : 353-359

Proneuronema gradatum sp. nov.

( Figs 7–12 )

Diagnosis. May be distinguished from other species by the following characters: crossveins in costal space in forewing present [absent in P. m inor sp. nov.]; M two to three times forked proximad third gradate series [once in P. minor sp. nov.]; dark pigmentation through outer gradate series present [absent in other species]; comparatively big size [its forewing 7.9–9.5 mm; 6.3–6.9 mm in P. m inor sp. nov.].

Description. Holotype SMF Be 2534 ( Figs 7 , 8 ). Head capsule completely missing, but large part of one antenna with about 50 flagellomeres preserved. Meso- and metathorax poorly preserved. Rest of body missing.

Forewing broadly oval, 9.5 mm long, 4.6 mm wide. Trichosors prominent all around wing margin. Costal space very broad, dilated proximally. Subcostal veinlets 22 in number, two of them simple, others once to three times forked. Humeral veinlet (basal-most subcostal veinlet) recurrent, pectinately branched, with eight branches (of these, five branches once forked in right wing; four branches once to twice forked in left wing). Four (right wing), five (left wing) crossveins form gradate series in proximal part of costal space. Presumable ScA distinct. Subcostal space moderately broad for entire length, with six crossveins in right wing: basal 1scp-r (located opposite to origin of humeral veinlet, poorly visible in right wing; not detected in left wing); two crossveins in middle of wing (2scp-r, 3scp-r); three in distal part. RA forked apically, with two branches each forked once or twice. RA space (between RA, RP) nearly as wide as subcostal space in its basal part. Three ORBs in both forewings. ORB1 once (left wing) or twice (right wing) deeply forked proximad third gradate series of crossveins), with branches directed anteriorly; of these, distal branch deeply forked proximad third gradate series in right wing. ORB 2 in right wing simple before fourth gradate series, once forked after; its origin located near origin of ORB3, touching near their origins for short distance. ORB 2 in left wing originating far from origin of ORB3. ORB3 (RP proper) originating slightly proximad 2scp-r in both wings, pectinate, with five branches originating proximad fourth gradate series in right wing (third branch of ORB3 twice forked between third, fourth gradate series). M appears not fused basally with R, forked proximad second gradate series. MA forked at fourth gradate series; anterior branch with marginal fork, posterior branch simple. MP deeply forked shortly proximad second gradate series; both branches not forked before marginal branching. Cu dividing into CuA, CuP close to wing base. CuA pectinately branched, with four (left wing) or five (right wing) branches, proximal-most branch deeply forked; all branches forked rather shallowly once or twice. CuP deeply forked, each branch with marginal fork (anterior branch in left wing twice forked). AA1 nearly straight, pectinately branched distally, with proximal-most branch forked once (left wing) or twice (right wing), and four simple short branches. AA2 pectinately branched, with six branches; of these, three (left wing) and four (right wing) branches forked (in right wing, two branches twice forked). AA3 very deeply forked; anterior branch shallowly forked, posterior branch simple. Four gradate series of crossveins (series 1–4 of Oswald 1993) posterior to RA. First (basal) gradate series consists of five crossveins (1mcu, 1icu, 1cu-aa, 1aa1-aa2, 1aa2-aa3); 1aa2-aa3 strongly shifted towards wing base than other crossveins; one additional crossvein between CuP, AA1 located proximad first series. Second gradate series consists of four (right wing) and five (left wing) crossveins (2r-m, 2im, 2m-cu, 2icu, 2icup (only in left wing). Third (‘inner’) gradate series consisting of 13 crossveins (in right wing), from RA to CuA. Fourth (‘outer’) gradate series complete, with 26 crossveins, from RA to AA1. Membrane with distinct color pattern consisting of dark brown spots near margins (except for humeral, anal areas), dark brown band through crossveins of fourth gradate series (from anterior branches of RP to CuA), and lighter spots all over wing.

Hind wing broad, 8.4 mm long, 3.8 mm wide. Costal space narrow, slightly dilated proximally, with all preserved veinlets simple. Humeral plate long, straight; covered with numerous fine setae, and few longer and stronger setae at top. ScP stout. No subcostal crossvein detected. RA space nearly equal in width for most length; crossvein 1ra-rp strongly oblique; other crossveins not detected. RP with eight pectinate branches, two of them originating before/at 1ra-rp; RP1 to RP3 dichotomously branched at or slightly proximad outer gradate series; other branches once to three times forked distad outer gradate series. Basal sinuous crossvein 1r-m very long, connecting RP, M slightly distad origin of RP1. M forked distad origin of RP1. MA, MP simple before marginal branching. Cu dividing into CuA, CuP very close to wing base. CuA nearly straight proximad CuA1, then markedly bent anteriorly; pectinately branched with six long branches; posterior trace of CuA with three pectinate branches directed anteriorly (two of these shallowly forked); other branches of CuA with shallow (marginal) forks. CuP thin, straight, with marginal fork. AA1 pectinate, probably with six branches; proximal-most branch heavily branched. AA2 incompletely preserved, pectinate, with short simple branches. AA3 not preserved. Three gradate series of crossveins posterior to RA. First (basal) series consists of five crossveins (1ra-rp, 1r-m, 1m-cu, 1cu-aa, 1aa1-aa2). Second (‘inner’) series consists of four crossveins, from RP4 to MA. Third (‘outer’) series consists of 12 crossveins running from RP to CuA, and two crossveins between CuA1 and AA2. Membrane hyaline with badly preserved color pattern.

Specimen SMF Be 376a ( Figs 9 , 10 ). Forewing oval with nearly rounded apex, 8.8 mm long, 4.3 mm wide. Trichosors prominent all wing margin round. Costal space very broad, dilated proximally. Vast majority of subcostal veinlets once or twice forked. Humeral veinlet (basal-most subcostal veinlet) recurrent, pectinately branched, with four branches (one deeply forked). Seven crossveins form gradate series in proximal part of costal space. Subcostal space moderately wide for entire length, with six crossveins (one basal, two intermediate, three distal). RA forked apically, with two branched, each forked once. RA space (between RA and RP) nearly as wide as subcostal space basally. Three ORBs. ORB1 (RP1) with two branches directed anteriorly proximal to third gradate series; ORB2 simple before fourth gradate series, then forked. ORB3 (RP proper) possesses five branches, originating proximal to fourth gradate series. M appears not fused basally with R. M dividing into MA, MP proximal to second gradate series; MA deeply forked at third gradate series; MP deeply forked just proximad second gradate series; all branches of M not forked before terminal branching. Cu dividing into CuA, CuP close to wing base. CuA pectinately branched, with four branches, CuA1 deeply forked. All branches of RP, M, and CuA have marginal forks. CuP deeply forked, each branch with marginal fork. AA1 rather deeply forked, anterior branch with three short simple pectinate branches; posterior branch only with marginal fork. AA2 probably pectinately branched (poorly preserved). AA3 not preserved. Four gradate series of crossveins (series 1–4 of Oswald 1993) posterior to RA. First series consists of one crossvein preserved (1icu), others not preserved. Second series includes six crossveins: 2r-m, 2im, 2imp, 2m-cu, 2icu, 1cu-a1. Third (‘inner’) series with twelve crossveins, from 3r1-rs to 3m-cu. Fourth (‘outer’) series complete, with 21 crossveins, from 4r1-rs to 4icup. Membrane hyaline; most crossveins in fourth series, and three posterior crossveins in third series margined with darker pigmentation; no other distinct maculation.

Hind wing fragmentary, 2.7 mm long, 3.2 mm wide (probably represents actual wing width). Costal space narrow, with all preserved veinlets simple. No subcostal crossvein detected. RA space proximally dilated (before RP2); crossvein 1r1-rs strongly oblique. Three branches of RP preserved, two of them originated before 1r1-rs. Basal sinuate crossvein r-m connects RP at origin of RP1, M. M forked distad origin of RP1. CuA stout proximad its branching; proximal-most branch of CuA forked twice; other branches apparently with marginal fork (two preserved). CuP thin, with marginal fork. AA1 probably pectinate.

Specimen No. 1545 ( Figs 11 , 12 ). Female. Body completely preserved, but most details poorly discernible. Antennae completely preserved; visible part of flagellum consists of 43 (left) and 46 (right) segments. Four distal segments of left maxillary palpus visible. Abdominal terminalia very crumpled, and segmentation not clear; gonostylus of gonoxcoxte 9 prominent, covered with scarce long setae ( Fig. 11 C).

Mesofemur, mesotibia visible, but their length cannot be measured. Metafemur ca. 1.1 mm Left metatibia relatively long (2.1 mm), only slightly swollen medially, with two short apical spurs (visible on left metatibia); right metatibia in its basal third slender, then broadens abruptly to at least twice basal thickness; and apically becoming again gradually more slender (right metatibia possibly abnormal). Four tarsomeres of metatarsus visible; basimetatarsus more than twice as long as each other visible tarsomere.

Forewing 7.9 mm long, width not measurable, slightly distorted. Trichosors distinct along entire wing margin. Costal space broad, dilated proximally; 19 subcostal veinlets present, but a few distal not discernible; most of them once to twice forked. Humeral veinlet strongly recurrent, pectinately branched, with two of five branches once forked (left wing). Gradate series of crossveins present in proximal part of costal space, with five discernible crossveins. ScA not discernible. Subcostal space only visible in distal part of wing, with one (distal) crossvein. In RA space, abnormally doubled crossvein 3ra-rp well discernible in left wing. RP with three ORBs. ORB1 twice deeply forked near crossvein 2r-m, with branches directed anteriorly and not forked before fourth gradate series; porterior trace of ORB1 forked proximad fourth gradate series. ORB2 shallowly forked distad fourth gradate series. ORB3 (RP proper) pectinate, with five branches, two of which forked proximad fourth gradate series. M forked proximad second gradate series. MA deeply forked at second gradate series, its anterior branch forked at level of third gradate series; distal part not visible. MP forked at level of third gradate series; distal part not visible. Proximal part of CuA and CuP not visible. CuA pectinately branched, probably with four long branches, but other details not visible. CuP fragmentarily discernible. Anal space not visible. Only three gradate series of crossveins visible, first series not visible. Of second gradate series, only crossveins 2r-m, 2icu visible. Of third (‘inner’) gradate series, 11 crossveins visible, from RA to CuA. Of fourth (‘outer’) gradate series, 16 anterior crossveins visible, from RA to posterior trace of M. Outer gradate series distinctly margined with brownish-colored membrane.

Hind wing ca. 6.9 mm long, width not measurable. Trichosors distinct along entire wing margin. All subcostal veinlets simple. RA space dilated proximally; crossvein 1ra-rp strongly oblique; other crossveins not detected. RP with seven (left wing), eight (right wing) pectinate branches, two of them originating before 1ra-rp; branches not forked proximad outer gradate series. Basal sinuous crossvein 1r-m very long, connecting RP1 and M slightly distad origin of RP1. Three gradate series of crossveins posterior to RA. Of first (basal) series, two crossveins (1rarp and 1r-m) discernible. Three crossveins discernible in second (‘inner’) series, from RP5 to RP2; other two to three crossveins possible. Crossveins of third (‘outer’) series not well discernible due to preservation. Membrane hyaline, no distinct color pattern.

Material. Holotype SMF Be 2534, deposited in SMF (formerly in the private collection of Thomas Weiterschan, former coll. No.1620). An incomplete specimen: mesothorax; one fragmentary antenna; completely preserved right fore- and hind wings; distal parts of left fore- and hind wings are missing.

Specimen SMF Be 376a, deposited in SMF (formerly in the private collection of Thomas Weiterschan, former coll. No. 1390). A fragmentary specimen (nearly complete right forewing, one fragmentary antenna, and fragmentary hind wing).

Specimen No. 1545, deposited in the private collection of Christel and Hans-Werner Hoffeins (Hamburg, Germany). A complete female specimen, with crumpled abdomen. Wings are completely preserved, but strongly overlapping and partly deformed, so only parts of the wing venation of the right wing pair can be clearly seen; the wing venation of the left wing pair is for the most part not visible.

Type locality and horizon. Baltic amber (precise collecting site unknown); late Eocene.

Etymology. From the Latin gradatus, gradate, in reference to the presence of the gradate series of crossveins in the forewing costal space.

Remarks. All these specimens are considered to belong to the same species as they have a similar size and their venation clearly differs from that of Proneuronema minor sp. nov. However, the holotype and other two specimens strongly differ from each other in their wing color pattern. These differences may not be sufficient reason for dividing the species into two, as many extant hemerobiid species have great intraspecific variability in wing color pattern. Some species have even stronger color pattern variability than in this new species, e.g., Megalomus stangei Gonzalez Olazo, 1981 (Gonzalez Olazo 1981: Fig. 4 ; Monserrat 2003: Figs 38, 39), M. moestus Banks, 1895 (Monserrat 1997: Figs 99, 100), Drepanepteryx punctata (Okamoto, 1905) , and Micromus sjostedti van der Weele, 1910 (Tjeder 1961: Figs 530–533). Nonetheless, the holotype on the one hand and other two specimens on the other may theoretically represent two distinct species. This problem will be resolved by the discovery of more complete specimens whose genitalia segments are easily discernible.

A specimen from Baltic amber that was previously erroneously referred to as “ Chrysopidae ” by Weitschat & Wichard (1998: Pl. 56c) and later as “second undescribed Megalomus -like species” by Makarkin et al. (2012) surely belongs to Proneuronema gradatum sp. nov. This specimen is deposited in a private collection, and currently inaccessible for study. Examination of the photograph in Weitschat & Wichard (1998) shows that the venation and color pattern are most similar to the specimen SMF Be 376a.

Figures

FIGURE 4. Proneuronema minor gen. et sp. nov., specimen SMF Be 2535 as preserved. A, right side. B, left side. Scale bar = 3 mm (both to scale).

FIGURE 7. Proneuronema gradatum gen. et sp. nov., holotype SMF Be 2534 as preserved (dorsal view). Scale bar = 1 mm.

FIGURE 8. Proneuronema gradatum gen. et sp. nov., wing venation of the holotype SMF Be 2534. A, right forewing. B, left forewing (color pattern is omitted; converted to standard right dorsal view). C, right hind wing. Scale bar = 1 mm.

FIGURE 9. Proneuronema gradatum gen. et sp. nov., paratype SMF Be 376 a as preserved. A, right forewing, fragment of antenna. B, fragment of right hind wing. Scale bars = 1 mm.

FIGURE 10. Proneuronema gradatum gen. et sp. nov., wing venation of the paratype SMF Be 376 a. A, right forewing. B, right hind wing. Scale bar = 1 mm (both to scale).

FIGURE 11. Proneuronema gradatum gen. et sp. nov., female specimen No. 1545 (Hoffeins’ collection). A, ventral view. B, dorsal view. C, apex of abdomen. st, gonostylus of gonocoxite 9. Scale bars = 2 mm (A, B to scale), 0.2 mm (C).

FIGURE 12. Proneuronema gradatum gen. et sp. nov., wing venation of the specimen No. 1545 (Hoffeins’ collection). A, left forewing, slightly distorted. B, left hind wing (both converted to standard right dorsal view). Scale bar = 1 mm (both to scale).