Myrmecolax aranealis, Zheng & Zhou, 2025

Zheng, Xuhongyi & Zhou, Changfa, 2025, Rediscovery of Myrmecolacidae from China with a new Myrmecolax species and a checklist of Chinese twisted-wing parasite (Insecta: Strepsiptera), Zootaxa 5646 (4), pp. 562-574 : 563-568

Myrmecolax aranealis sp. nov.

urn:lsid:zoobank.org:act:23003788-335D-466E-8E09-C2D833968EDB

( Figs 1–5)

Description of holotype. Total body length ca. 2.00 mm. Body generally dark brown ( Fig. 1A–C).

Head width ca. 0.68 mm, densely covered with microtrichia ( Fig. 2A). Compound eye semiglobular, dark brownish, width ca. 0.25 mm, distance between eyes ca. 0.30 mm ( Fig. 2A). Each compound eye with ca. 23 semiglobular ommatidia, interval between ommatidia with dense microtrichia ( Fig. 2B). Connecting area of compound eye and sclerotized head capsule pale and unsclerotized ( Fig. 1A–C). Frons dark brown, strongly protruded, dorsally separated from head capsule by distinct suture, base of antennae pale ( Fig. 1A). Antenna dark brownish and 7-segmented, all antennomere densely covered by microtrichia, antennomere III–VII exhibit fine punctation; antennomere I–IV with short base, antennomere III with extremely slender and flat flabellum, ca. 1.40 mm in length, subequal to combined length of antennomere V–VII; antennomere V–VII slender and flat, ca. 0.50 mm, 0.40 mm and 0.50 mm respectively ( Fig. 2A). Mouthfield sclerite (fused mouthparts) with a round opening, shield-shaped and brownish, surrounded by unsclerotized light-colored area ( Fig. 2A). Mandible slender palp-shaped, ca. 0.26 mm, light brownish, slightly curved, translucent and expanded apically ( Fig. 2A). Maxillary palp 2-segmented, dark brown, basal segment short, ring-shaped; apical segment slender palp-shaped, slightly curved with a blunt apex, ca. 0.38 mm, much broader than mandible ( Fig. 2A).

Pronotum dark brownish and sclerotized, ring-shaped, width ca. 0.30 mm, densely covered by microtrichia ( Fig. 1A–C). Mesonotum similar to pronotum ( Fig. 1A–C). Metathorax strong and dark brownish, width ca. 0.40 mm ( Fig. 1A–C). Proscutum nearly pentagon with rounded anterior margin, scutum separated into two nearly rectangular lateral areas and one nearly triangular anterior area by deep sutures ( Fig. 1A–C). Scutellum subtriangular and rounded ( Fig. 1A–C). Postlumbium lip-shaped and light yellowish. Postscutellum cup-shaped in dorsal view with a straight posterior margin, half-cup shaped in lateral view, bending downwards posteriorly ( Fig. 1A–C). In lateral view, scutellum surrounded by white area; anterior area of epimerom with a slender and curved white band which surrounding detached yellowish postalare process; epimerom and anepisternum separated by a dark sclerotized suture, anepisternum and katepimerom separated by a slender white area ( Fig. 1C).

Forewing (halter) slender and weakly sclerotized, ca. 0.50 mm, slightly flattened but expanded apically, apex ovoid ( Fig. 1A–B). Hindwing broad and fan-shaped, ca. 1.90 mm in length, densely covered by microtrichia, translucent pale brown, with dark brown veins ( Fig. 3A–B). C and Sc almost fused, reaching ca. 1/2 of anterior margin; R 1 thick, ending at ca. distal 1/3, slightly hooked apically; R 2 detached, distally bifurcated, with anterior branch directed to wing base but not reaching R 1 apex, posterior branch ca. 2× the length of anterior branch; R 3 detached, ca. 1/2 wing length; R 4 and R 5 almost fused with each other; R 4 weak, ending at middle; R 5 proximally detached, almost reaching distal margin; MA and CuA almost parallel; CuP weak, almost parallel to anal margin, reaching tornus ( Fig. 3A–B).

Legs densely covered by microtrichia, brownish, tarsi slightly paler ( Fig. 4A–C). Base of each tarsus surrounded by numerous irregular pale dots ( Fig. 4A–C). Foreleg with broad and flat coxa (ca. 0.40 mm), slender and flat femur (ca. 0.40 mm), slender conical tibia which slightly expanded and has a suture apically (ca. 0.33 mm), and 4-segmented tarsus without tarsal claw (ca. 0.25 mm) ( Fig. 4A); tarsomere I–IV gradually shorter, tarsomere I trapezoidal, tarsomere II–IV conical, apical ventral margin of tarsomere I–IV extend into broad and square-shaped lamellae which densely covered by microtrichia ( Fig. 4D). Structure and length ratio of midleg similar to foreleg, but midleg slightly stronger and longer ( Fig. 4B, E). Hindleg short and stout, trochanter of hindleg small and globular, femur flat oval (ca. 0.25 mm), tibia stout conical (ca. 0.25 mm), tarsi 4-segmented, tarsomeres similar to foreleg and midleg but shorter and wider, width subequal to tibia ( Fig. 4C, F).

Abdomen dark brown, 10-segmented, each segment densely covered by microtrichia, paler dorsally ( Fig. 5A– B). Segment I–III covered by postscutellum ( Fig. 5A–B). Segment IX large and strongly sclerotized, elliptical in caudal view, extending ventrally as an elongate and grooved subgenital plate ( Fig. 5A–B). Segment X small and shovel-shaped ( Fig. 5A–B). Aedeagus ca. 0.30 mm, hook-like, strongly curved at basal 1/4, dorsal margin of corner slightly protruded; both apical dorsal hook and apical ventral projection sharp, subequal in length, ventral projection thicker, dorsal hook directed from aedeagus by a 45° angle ( Fig. 5C).

Material examined. Holotype: male adult, China: Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Mengla County, Man-Pa Village , 21°30'53.19'' N, 101°32'48.45" E, 727 m a.s.l., 21.III.2025, Xuhongyi Zheng leg.

Diagnosis. The new species can be attribute to Myrmecolacidae by having single CuA in hindwing, foursegmented tarsi without tarsal claw, and by having a seven-segmented antennae, which has a long flabellum on antennomere III, a short antennomere IV, and slender antennomere V–VII. Among the three extant genera within Myrmecolacidae , it can be recognized as a Myrmecolax member by the detached R 2 and R 3 in hindwings.

Male adult of Myrmecolax aranealis sp. nov. is characterized by: (1) large body size, ca. 2.0 mm in length; (2) slender flabellum of antennomere III, which almost reaching the apex of antennomere VII; (3) expanded and rounded apex of mandible; (4) blunt apex of maxillary palp; (5) hindwing venation, with single R 3, R 4 almost fused with R 5, single MA, slender CuP reaching tornus, and bifurcated R 2 which has anterior branch not reaching R 1 apex and posterior branch ca. twice the length of anterior branch; (6) flat and broad lamellae on all tarsomeres; (7) basally curved aedeagus with sharp dorsal hook and sharp apico-ventral projection, which are subequal in length.

Compared with the reported 15 Asian Myrmecolax species, M. aranealis sp. nov. can be easily distinguished from other species by its long antennomere III, hindwing venation or aedeagus shape, except M. furcatus Bohart, 1951 and M. plantipes (Chaudhuri, 1978) , from Philippines and India respectively. It can be separated from M. furcatus by a larger body (wingspread of M. aranealis sp. nov. more than 4.0 mm, M. furcatus ca. 3.28 mm), shorter anterior branch of R 2 (anterior branch longer than posterior branch and reaching the end of R 1 in M. furcatus ), longer CuP which reaching the tornus, and more curved and protruded aedeagus base. It is distinguishable from M. plantipes by a larger body ( M. aranealis sp. nov. ca. 2.0 mm, M. plantipes ca. 1.0 mm), antennomere VI + VII longer than antennomere V, and narrowed base of aedeagus.

Etymology. The specific epithet is derived from the Latin word aranea (spider), in reference to the collection of the holotype from a cobweb.

Distribution. China (Yunnan).

Biological notes. The male holotype of the new species was discovered on a spider web over a small stream in a forest, together with several mayfly adults ( Caenidae ) at the same web, at around 2:00 PM Beijing time ( Fig. 6). The day was sunny, the temperature on that day was 14℃-25℃. The male insect was still full of vitality and was struggling to get out when discovered, and the spider web still fresh and undamaged. We guess it was trapped within three hours .