Rainieria tenebrosa Kim & Lee, 2022

Kim, Wonwoong, Weele, Ruud Van Der & Lee, Seunghwan, 2022, New records of Micropezidae (Diptera, Acalyptratae) from South Korea, with description of a new species of Rainieria Rondani, Zootaxa 5178 (1), pp. 26-40 : 29-34

Rainieria tenebrosa Kim & Lee sp. nov.

( Figs 2A–H , 3E–F , 5B, 5E , 6B , 8D )

Diagnosis. Recognized by brownish black body; wing membrane light brown with fuscous discal band ( Fig. 8D ); all tibia and tarsus uniformly dark brown, except white tarsomeres 1–4 of front legs; pleural membrane dark brown without conspicuous white patch under T3–4 ( Fig. 3E–F ); distinctly shaped male S5 as in ( Fig. 5B ).

Description. Total body length 7.2–9.0 mm in males, 7.9–9.6mm in females.

Head: Globose, color mostly black with exception of silvery ventral portion of parafacial; pedicel with a long ventral bristle, short bristles dorsally; arista bare; frontal vitta velvety black with silvery pruinescence posteriorly; slightly tapering posteriorly and anteriorly; clypeus shiny, strongly convex and protruding as long as the position of lunule; head chaetotaxy: well-developed 1-2 frontal bristles of similar length; 1 orbital bristle, slightly longer than the frontal bristle; strong inner vertical, outer vertical, and postocellar bristles present; postgenal setae short, weak, and sparsely distributed.

Thorax: Shining black with exception of anepisternum and katepisternum covered with silverly microtrichae; all thoracic bristles black; thorax chaetotaxy: well-developed one dorsocentral bristles; 2 notopleural, 1 supralar, 1 postalar, and 1 scutellar bristles present; posterior part of katepisternum with rows of strong suberect bristles; legs: fore coxa brown, becoming pale distally; mid and hind femora black with one yellowish brown preapical ring; all tibia and tarsus uniformly dark brown, with the exception of white fore tarsomeres 1–4 and darkened tarsomere 5; wing: evenly infuscate with a dark discal and apical band; halter dark brown, knob darker.

Abdomen: All tergite and sternite uniformly shining dark brown; bristles on syntergite 1+2 erect, light brown, in remaining tergites and oviscape black microsetulose; abdominal membrane uniformly dark brown with relatively pale region below T 3 in males, T 3–4 in females; male with pleural sac below syntergite 1+2; female oviscape shiny black with posterior tip reddish brown.

Male. Genital fork (Sternite 5) relatively stout, length of individual arm as long as the length of basal area; arms strongly incurved, inner margins packed with dense short, stout black setae; arms almost touching the other at the distal end; basal area of the fork with a narrow triangular cleft; blade of ejaculatory apodeme about as large as the epandrium, elliptical shaped and subequal in height to the width including the sperm pump; phallapodeme triangular-shaped, hypandrium with a short anterior plate; distal distiphallus elongate but not reaching the anterior end of hypandrium, distal end blunt.

Female. Spermathecae with two ducts, the duct leading to the paired spermatheca twice as long as the latter; single spermatheca capsule-shaped, relatively small compared to the paired spermatheca; branching duct leading to the paired, spherical spermatheca long and convoluted.

Holotype. South Korea: Gyeonggi-do: 1♂, Uijeongbu-si, Jangam-dong, Mt. Suraksan (37°42'19.4"N 127°04'57.4"E) displaying on bark of Quercus cf. dentata Thunb. 14.vi.2021, coll. Wonwoong Kim and Jae Seok Oh ( SNUM)

Paratypes. South Korea: Gyeonggi-do: 1♂, 10♀, same data as holotype ( SNUM) ; 1♀, same data as holotype ( NIBR) ; 2♂, 3♀, same locality as holotype, 09.viii.2021, coll. Jae Seok Oh ( NIBR) ; 1♀, Gapyeonggun, Cheongpyeong-myeon, Goseong-ri , Mt. Homyeongsan , Alt. 220m . (37°43'16.3"N 127°29'23.4"E) 26.vi– 16.vii.2009, Malaise Trap. coll. Jongok Lim ( SNUM) ; 1♂, 5♀, Yongin-si, Cheoin-gu, Yangji-myeon , Hanteo-ro 454beon-gil, 48 (37°25'70.2"N 127°25'78.0"E) displaying on bark of recently dead Quercus sp. 02.vi.2022, coll. Wonwoong Kim ( SNUM) . Gangwon-do: 4♀, Pyeongchang-gun, Unduryeong-ro , 313 (37°43'08"N 128°26'44.9"E) 16.vi–31.viii.2019, Malaise Trap. coll. M. Lee and Park ( SNUM) .

Comparative material examined. Rainieria calceata (Fallén, 1820) - Hungary: 1♂, Pillis, Unknown date, vii. 2001, coll. Ruud van der Weele ( SNUM); 1♀, Hills of Budapest, 09.vii.1992, coll. Ruud van der Weele ( SNUM) .

Etymology. From Latin word tenebrosum (=dark), referring to the distinctive black coloration among congeners.

Distribution. South Korea (Gangwon-do, Gyeonggi-do)

Remarks. This new species can be confused with Rainieria calceata (Fallén, 1820) due to overall coloration, the shape of the male S5, and female sternite shape. However, it is easily distinguished from R. calceata by the following characteristics: uniformly dark brown hind tarsomeres; differences in the curvature of arm, narrower cleft of the fork, and short stout setae of uniform density in male S5 ( Fig. 5B–C ); oval-shaped blade of ejaculatory apodeme; shorter epandrium and distal distiphallus; phallic bulb almost reaching the base of epandrium, which in calceata only reaches the middle half of the epandrium ( Fig. 5F ); presence of short plate of hypandrium; blunter tip of distal distiphallus, which in calceata is distinctively sharpened ( Fig. 5F ).

Biology. As in many Taeniapterinae , this new species is an apparent mimic of Ichneumonidae morphologically and behaviorally ( Marshall 2012). A number of individuals were observed at a shaded forest edge performing a foreleg-waving behavior to imitate the antennae of Ichneumonidae . In several field surveys, this species was found feeding on the flowing sap of Quercus cf. dentata Thunb. and Zelkova serrata (Thunb.) , plus a wet decaying plant mass.

Observed mating behavior involves courtship dance, bubbling and fluid exchange, and inter-sex competition. Copulation is triggered by the male following the female while moving its abdomen up and down vigorously. If the female is unresponsive, the males were observed to forcefully mate by grabbing the female with its front legs while approaching from behind. When the female allows mating, it lowers the body and opens the wings perpendicularly to the body. The male then uses the genital fork to ‘hook’ the female’s oviscape and lifts it to face the male’s genital segment, followed by the insertion of the aedeagus. The male engages in ‘kissing’ the female’s frons and labium repeatedly while shaking up and down vigorously, in which the female assists by facing its labium upwards ( Fig. 2F ). This kissing behavior involves the exchange of fluid between the pair, and the sex which offers the regurgitated fluid ( Fig. 2E ) and the one which imbibes the fluid produced by its partner switch multiple times during mating. The pair often enters a stationary phase where they do not engage in noticeable behaviors. After the copulation is over, the female would try to push the male away with its front legs and the male is often dragged behind the female before dissociation. Copulation was recorded to last over 20 minutes, excluding courtship.

The pleural sac of the male is inflated during courtship and mating, which possibly denotes a pheromone dispersing as suggested by Marshall (2012). If another individual approaches the mating pair, the male or the female would use its middle leg to wave off the intruder ( Fig. 2G ). Multiple mating incidents involving noticeable size difference among the opposite sex was observed ( Fig. 2C–D ).

Currently known oviposition preference of Rainieria species includes Ulmus americana L. ( Ulmaceae ), Fagus sp. (Fagoideae) , Betula sp. (Betulaceae) , and Abies sp. (Pinaceae) ( Sabrosky 1942; Krivosheina & Krivosheina 1996; Skidmore 2005). In our field observation, the females oviposited on a narrow cleft between the live and decomposing tissue of a standing Quercus cf. dentata Thunb. ( Fig. 2H ) and recently logged unidentified Quercus species. It is possible that oviposition on this particular site is preferred since the mix of a constant supply of tree sap and the decomposing tissue can provide both the nutrient and the substrate for the larvae to develop. Individual females were found on a dead fallen Carpinus laxiflora (Siebold & Zucc.) (Betulaceae) , possibly searching for an oviposition site. At an optimal site, the ‘aggregation oviposition’ was observed, where up to 15 individuals oviposited at a small patch ( Fig. 2H ). Subtle competition among females, often waving their legs to deter other individuals, was observed in such sites.

Figures

FIGURE 2. Rainieria tenebrosa, live individuals. A, female; B, male; C, mating pair, with smaller male; D, mating pair, with smaller female; E, bubbling behavior of female during copulation; F, fluid exchange during copulation; G, male waving the intruder away during copulation; H, ‘aggregation oviposition’ on a bark of Quercus cf. dentata Thunb. [Figure D provided by Jae Seok Oh (SNU)]

FIGURE 3. Lateral habitus and spermathecae of Rainieria species. A, Rainieria calceata, male; B, ditto, female; C, Rainieria triseta, male; D, ditto, female; E, Rainieria tenebrosa, holotype male; F, ditto, paratype female; G, ditto, spermathecae and associated structures.

FIGURE 5. Male genital structure of Rainieria species. A, D: Rainieria triseta; B, E: Rainieria tenebrosa; C, F: Rainieria calceata. A–C, Male Sternite V (Genital fork); D–F: Various structures of male terminalia. Abbreviations: aa—phallapodeme; bd—basal distiphallus; c—cercus; dd—distal distiphallus; e—epandrium; ea—ejaculatory apodeme; ed—ejaculatory duct; h—hypandrium; pb—phallic bulb.

FIGURE 6. Female sternite structure of Rainieria species. A, Rainieria calceata; B, Rainieria tenebrosa; C, Rainieria triseta; D, ditto, ventral view of alcohol-preserved specimen. Note the reduction of sternite III–IV.

FIGURE 8. Wings of Korean Micropezidae species. A, Micropeza soosi; B, Compsobata dentigera; C, Rainieria triseta; D, Rainieria tenebrosa; E, Mimegralla suzukiana.