Siobla iridipennis Malaise, 1934

Niu, Gengyun & Wei, Meicai, 2021, Review of some Siobla (Hymenoptera: Tenthredinidae) species, Zoological Systematics 46 (3), pp. 208-224 : 218-223

Siobla iridipennis Malaise, 1934 ( Fig. 14 )

Siobla iridipennis Malaise, 1934: 23 ; Malaise, 1945: 117–118.

Description. Holotype ♀. Body length 9.0 mm ( Figs 14a–c ). Yellow brown, following parts black: head and antenna entirely, narrow lateral margin of pronotum, bottom of parapsis, metapostnotum, propleuron, ventral half of mesepisternum, middle of mesepimeron, metapleuron except for dorsal margin and small posterior corner, narrow anterior margin of tergite 2, narrow base of basal ovipositor sheath and most of apical ovipositor sheath; legs black, apical half of fore femur on anterior side, ventral side of fore tibia and of tarsus, ventral side of middle tarsus pale brown; most of middle femur and hind femur except for extreme apex yellow brown. Wing evenly infuscate, with feeble purple reflection, paler toward apex, pterostigma and veins black brown. Hairs on head black brown, hairs on dorsal of thorax pale brown and on mesopleuron brown, setae on sheath pale brown.

Punctures on clypeus large and sparse, interspaces broad and smooth ( Fig. 14f ); punctures on dorsum and lateral of head denser, with narrow but distinct smooth interspaces ( Figs 14e, g ); frons, lateral fovea and middle fovea densely punctured, with very narrow interspaces; interspaces between punctures on middle of inner orbit about as broad as diameter of a puncture, smooth and shiny; punctures dense on anterior of mesoscutal middle lobe, large and sparse on middle and posterior area, interspaces smooth and broader than diameter of a puncture; punctures on mesoscutal lateral lobe smaller and denser ( Fig. 14h ), interspaces smaller than diameter of a puncture, top area with feeble microsculptures; punctures on anterior slope of mesoscutellum shallow and sparse, interspaces smooth and as broad as a puncture, strongly shiny; posterior third of mesoscutellum coarsely punctured, mesoscutellar appendage smooth on middle and microsculptured laterally; punctures on metascutellum large and sparse, shiny; metapostnotum densely microsculptured, feebly shiny; punctures on propleuron minute and sparse ( Fig. 14i ); upper half of mesepisternum coarsely and densely punctured, anterior margin sparsely punctured, punctures on ventral half of mesepisternum minute and very sparse, interspaces broad and shiny, a large ventral anterior corner of mesepisternum smooth and shiny; middle of mesepimeron with large and dense punctures, bottom of anepimeron and most of katepimeron densely microsculptured, posterior margin of katepimeron smooth; dorsum of metepisternum evenly punctured, without microsculpture, ventral of metepisternum smooth and shiny; depressed part of metepimeron with shallow punctures and fine microsculptures, dorsal margin with dense punctures, posterior corner smooth; abdominal tergites 1 and 2 quite smooth ( Fig. 14j ), small middle area with several punctures; other tergites with dense and large punctures, interspaces smaller than punctures, surface smooth, strongly shiny.

Hairs on dorsum of head 2 times as long as diameter of lateral ocellus, hairs on mesopleuron about 2.2 times diameter of lateral ocellus. Clypeus about 2 times as broad as long, middle length distinctly longer than lateral length, apical margin roundly protruding ( Fig. 14f ); distance between eyes at level of toruli 1.2 times longest axis of eye; malar space 0.6 times diameter of lateral ocellus; middle fovea broad and deep, lateral fovea small and narrow, much deeper than middle fovea; supraantennal tubercle distinctly elevated, broader than high and about as high as frontal wall; frontal wall low and obtuse; interocellar furrow deep and narrow, postocellar furrow shallow, lateral furrows fine, weakly curved and slightly divergent backwards; postocellar area flat, clearly lower than top of ocelli, without middle ridge, broader than long (1.5: 1); in dorsal view temple almost as long as eye (0.95: 1), lateral sides weakly bent and slightly convergent backwards ( Fig. 14e ); occipital carina low and weak, complete. Antenna 0.9 times as long as head and thorax together, clearly shorter than abdomen or vein C, pedicellum 1.2 times as long as broad, antennomere 3 about 1.9 times as long as antennomere 4, outer side of antennomeres 5–8 with distinct longitudinal furrow, subapical antennomeres clearly enlarged, antennomere 7 about 1.3 times as long as broad. Middle furrow of mesoscutal middle lobe deep; mesoscutellum weakly elevated, much broader than long (1.8: 1), without peak and carina, posterior slope almost flat; mesoscutellar appendage flat, without middle carina. Metapostnotum with a sharp middle ridge and merged with middle process of first tergite, about as high as metascutellum; middle of mesepisternum distinctly elevated, ventral spur absent. Legs slender, hind tibia 1.2 times longer than tarsus, apex as broad as breadth of apical sheath in lateral view, inner apical spur 0.5 times as long as metabasitarsus; metabasitarsus slender, 5 times as long as broad, as long as following 3 tarsomeres together; tarsal pulvilli developed, about half as long as apical breadth of each tarsomeres, distance between basal 2 pulvilli 1.8 times as long as second pulvillus ( Fig. 14l ). Forewing with vein R clearly shorter than free part of Sc and about 0.33 times length of vein R+M, vein R+M 2 times as long as first absccisa of vein Rs, vein 2r strongly curved, vein cu-a meeting cell 1M at basal 0.2, pterostigma 1.2 times as long as cell 1Rs; stalk of hind anal cell about 0.33 times length of vein cu-a. Sheath 1.25 times as long as middle tibia, apical sheath 1.5 times as long as basal sheath ( Fig. 14k ), setae on sheath long and dense, distinctly curved in dorsal view. Lancet ( Figs 14m – n ) with 14 serrulae, spiculella distinct, middle serrulae distinctly convex and with 18–22 small distal teeth, proximal basal tooth absent, cypsela clearly shorter than serrula.

Male. Unknown.

Primary type examined. 1♀, holotype (BMNH): “ Tibet, Tropde , 11000ft., 23.VI.1924, Maj. R. W. G. Hingston ”; “Everest Exp. Brit. Mus., 1924. 386”; “ Siobla iridipennis n. sp. (Type), Malaise det., 1933”; “Typus (coll. BMNH)” .

Distribution. China (Tibet (Tropde)).

Remarks. The species is rare found. Malaise (1934) simply described the species based on a female specimen in a key to Siobla species. After then there is no additional collecting record about the species. Malaise (1945) keyed the species again but the description was still simple and most characters were not mentioned.

Siobla iridipennis is undoubtedly a species of Siobla as shown by the metabasitarsus distinctly compressed, the anterior margin of clypeus roundly protruding, anal cross vein of forewing oblique and at middle of the broad anal cell, and female lancet quite long and slender. However, Siobla iridipennis is remote from its congeners by the following characters: head subquadrate, temple distinctly elongated; sheath with dense setae, lancet with distinct spiculella; mesoscutellum quite flat and sparsely punctured; antenna stout and short; body yellow brown including head and antenna entirely, the ventrum of thorax black.

Siobla iridipennis was placed in Siobla ferox group in the paper of Niu & Wei (2010a), based on the simple original description of Malaise (1934, 1945). However, it is unique in body color and structure as discussed above. It seems that S. iridipennis is possibly a basal lineage of the genus. So it is necessary to propose a new species group, Siobla iridipennis group, for the species.

Funding The research was partly supported by the National Natural Science Foundation of China (31501885, 31672344, 31970447).

Acknowledgements Our cordial thanks are due to Dr. David R. Smith of USNM, Dr. Natalie Dale-Skey of BMNH, Dr. Zombori of HNHM, Dr. Hege Vårdal, the curator of Hymenoptera Collection, Naturhistoriska riksmuseet, Sweden in lending us type material of Siobla species and their help when we visited the museums. Our thanks are also due to anonymous reviewers.

Figures

Figure 14. Siobla iridipennis Malaise, 1934, ♀, holotype. a. Dorsal view. b–c. Lateral view. d. Labels. e. Head in dorsal view. f. Head in frontal view. g. Head in lateral view. h. Thorax in dorsal view. i. Thorax in lateral view. j. Abdominal tergites in dorsal view. k. Sheath. l. Claw. m. Lancet. n. Middle serrulae. Scale bars=1mm.