Largusoperla acus, Chen & Wang & Du, 2018

Chen, Zhi-Teng, Wang, Bo & Du, Yu-Zhou, 2018, Discovery of a new stonefly genus with three new species from mid-Cretaceous Burmese amber (Plecoptera: Perlidae), Zootaxa 4378 (4), pp. 573-580 : 575

Largusoperla acus sp. nov.

( Figs. 1–7 )

Diagnosis. As for the genus, except for the strongly constricted apex of paraproct.

Description. Macropterous; body length (excluding antennae and cerci) ca. 9.0 mm, slender, generally yellow and patterned with brown ( Fig. 1 ).

Head ( Figs. 1, 2 ): Head rounded and mostly brown, with paired bulging eyes and three black-ringed ocelli, anterior ocellus smaller than posterior ones and together forming an equilateral triangle. Antennae mostly brown, hairy and filiform, slightly shorter than abdominal length, with 30 to 38 segments and apical segments thinner than basal ones. The maxillary palps slender and longer than the labial palps.

Pronotum ( Figs. 1–3 ): Pronotum slightly narrower than head, rugose, mostly brown except for the pale median band, near reverse trapezoidal in shape with sharp corners, width longer than length. Mesothorax and metathorax sclerotized, with similar length to prothorax; meso- and metathoracic gill remnants visible. Forelegs shortest, hindlegs longest; femur and tibia mostly brown except for the pale apices; tibia slightly longer than femur, ventroapically with two slightly enlarged spurs; tarsi three-segmented, first two segments shortest, equal in size and with conspicuous euplantulae; claws simple, with pointed and dark apex.

Forewings ( Figs. 1, 4 ): Right forewing length 8.3 mm, width 4.0 mm. ScP about three-fourth of total wing length, reaching ScP+RA beyond ra-rp; area between anterior margin and RA with two crossveins; 12 crossveins present between ScP and the anterior margin. RP originated from mid-RA and with three branches. M forked at apical one-third of the wing length and with two branches; ra-rp connected with the opposite crossvein rp-ma. Cu forked to CuA and CuP, CuA forked basal to the fork of M, with three branches; CuP simple and near straight; area between M and CuA with six crossveins and 1.5 times wider than area between CuA and CuP, which with only three crossveins in right forewing and four in left forewing. AA1 simple, AA2 two-branched.

Hind wings ( Fig. 1 ): Wings length 7.1 mm, width 3.5 mm. ScP reaches RA slightly before ra-rp; area between anterior margin and ScP with three crossveins; fewer crossveins present between ScP+RA and the anterior margin. Apical parts of RP, M and Cu veins with similar forks like forewings; three crossveins present between anterior margin and RA.

Abdomen ( Figs. 1, 5–7 ): Abdomen near half the length of the body, each segment with dark lateral marks and extended posterolateral margins. Sternum 9 extended backwards, posteromedially with a slightly elevated transverse lobe. Tergum 10 seems cleft or with median membranous area, without projected hemiterga. Paraproct broad, strongly sclerotized and strongly upcurved, subapically constricted to a needle-like giant spine. Abdominal tip with a rounded, membranous aedeagus-like structure, which has a fork-shaped sclerite posteromedially. Cerci hairy and short gradually elongated and narrowed from base to apex, with 9 to 10 segments and each segment with a lateral cluster of long setae.

Type material. Holotype male, NIGP167158. This specimen is mostly wizened, especially the abdomen dorsally, details of which are scarcely visible. Consequently, the separation of tergum 10 might be a result of the decay, or may be considered an autapomorphy of this new genus. In addition, most parts of hind wings are overlapped under forewings, therefore not completely visible, but the apical veins are clear.

Etymology. The specific epithet means “needle” in Latin, which refers to the needle-shaped apex of paraprocts.

Syninclusions. Plant remains, approximately ten minute unidentified Coleoptera, Hymenoptera, and Diptera.

Figures

FIGURES 1–7. Largusoperla acus sp. nov., holotype male. 1. HabituS, dorSal view; 2. ReconStruction of head and pronotum, dorSal view; 3. TarSal SegmentS of right hind leg; 4. Right forewing; 5. Terminalia and itS reconStruction, lateral view; 6. Terminalia and itS reconStruction, dorSal view; 7. Terminalia, dorSolateral view.