Review of the scorpionfly genus Dicerapanorpa Zhong & Hua (Mecoptera: Panorpidae), with descriptions of two new species

The current knowledge of the scorpionfly genus Dicerapanorpa Zhong & Hua, 2013 is taxonomically reviewed. Two new species of Dicerapanorpa are described and illustrated, increasing the species number of this genus to 20. Dicerapanorpa bifurcata sp. nov. from the Minshan Mountains, Sichuan Province, is characterized by the absence of the paramere basal branch and the elongated mesal branch in males, and the medigynium having a short basal stalk in females. Dicerapanorpa zhengkuni sp. nov. from the Wuling and Miaoling Mountains, Guizhou Province, is distinguishable by the greatly elongated hypovalves, the very short basal branch of the paramere, and the dorsomedially curved lateral branch in males, and the rounded main plate of the medigynium in females. An updated key to species of Dicerapanorpa is presented.


Introduction
Panorpidae Latreille, 1805 is the most speciose family of Mecoptera Packard, 1886, with more than 480 species in the world (Penny & Byers 1979;Bicha 2018;. They are commonly known as scorpionflies, because their enlarged and recurved male genitalia resemble the stinger of scorpions (Byers & Thornhill 1983;Dunford & Somma 2008). Panorpids usually occur in mesic forests in mountainous regions and mainly feed on dead arthropods and vegetative material (Palmer 2010).
Panorpidae currently consists of eight extant genera (Gao & Hua 2019;Hu et al. 2019c;. Panorpa Linnaeus, 1758 (with ca 260 spp.) is distributed in Asia, Europe and North America. Neopanorpa van der Weele, 1909 (with ca 170 spp.) is limited to the Oriental Region (Wang & Hua 2017Wang & Hua 2018). Leptopanorpa MacLachlan, 1875 (with 14 spp.) is restricted to Java and Sumatra of Indonesia (Wang & Hua 2020). The remaining five genera (Sinopanorpa Cai & Hua, 2008, Furcatopanorpa Ma & Hua, 2011, Dicerapanorpa Zhong & Hua, 2013, Cerapanorpa Gao, Ma & Hua, 2016and Megapanorpa Wang & Hua, 2019 are endemic to China (Cai et al. 2008;Zhong & Hua 2013;Hu et al. 2015;Gao et al. 2016;Miao et al. 2019;. The genus Dicerapanorpa Zhong & Hua, 2013, erected for the Panorpa diceras group (Cheng 1957), comprises 18 described species to date Hu et al. 2019aHu et al. , 2019c. The monophyly of Dicerapanorpa was confirmed by molecular (Hu et al. 2015;Miao et al. 2019) and morphological studies (Ma et al. 2009(Ma et al. , 2012. The genus can be readily recognized by male adults with two finger-like anal horns on the posterior margin of abdominal tergum VI and the trifurcated paramere of genitalia, and females with concealed axis of medigynium (Cheng 1957;Zhong & Hua 2013). Considerable variations within Dicerapanorpa were found in the wing pattern (Liu et al. 2016), the number of female ovarioles (Hou & Hua 2008) and the male salivary gland tubes . The male adult initiates copulation by grasping the female with a notal organ on the posterior margin of the third abdominal tergum and two anal horns on the posterior margin of the sixth tergum, and prolongs copulation by offering salivary masses as nuptial gifts (Zhong et al. 2015). The larvae of Dicerapanorpa are eruciform with annulated processes, reflecting the adaptive significance for fossorial and soil-living habits (Ma et al. 2014;Jiang et al. 2019).
The species of Dicerapanorpa are distributed in the Hengduan Mountains and the adjacent Qinling-Bashan Mountains (Fig. 1), and can be categorized into two groups Hu et al. 2019a, Fig. 1. Geographical distribution of Dicerapanorpa Zhong & Hua, 2013. The white dots represent the type locality of D. bifurcata sp. nov., the white asterisks indicate the type locality of D. zhengkuni sp. nov., and the red dots represent the distribution of the known species of Dicerapanorpa. 2019b, 2019c). The D. magna group is restricted to the Qinling, Bashan, and Minshan Mountains, and is characterized by the yellowish wing membrane with distinct wing markings and the rostrum without distinct lateral stripes. In contrast, the D. diceras group is distributed in the Hengduan Mountains, and is distinguishable by the hyaline wing membrane and the rostrum with two distinct lateral stripes.
In this paper, two new species are described from the Minshan Mountains, Sichuan Province, and the Wuling and Miaoling Mountains, Guizhou Province, China (Fig. 1), respectively, thereby raising the species number of Dicerapanorpa to 20. In addition, we updated the key to species of Dicerapanorpa.

Material and methods
The specimens were examined using a Nikon SMZ-168 microscope. Female medigynia were macerated in 5% NaOH for 3 min, and rinsed with distilled water. Images of habitus were taken with a Nikon D7000 digital camera. Other photographs were taken using an Auto-montage imaging system AxioCam IC attached to a ZEISS SteREO Discovery.V20 stereo microscope. All the images were further processed and assembled with Adobe Photoshop CS6. The length and width of the left wing were measured with a vernier caliper.
All the specimens examined are preserved in 75% or 100% ethanol in -20°C freezers. All material is deposited in the Entomological Museum, Northwest A&F University, Yangling, China (NWAU).
Abbreviations A1 = first abdominal segment (and so forth for other segments) T1 = first tergum (and so forth for other terga)

Diagnosis
This species can be readily recognized by the following characters: basal branch of male paramere absent; mesal branches elongated, convergent distally, and extending to the median tooth of gonostylus; lateral branch curved semicircularly at base and convergent at apex, exceeding basal process of gonostylus (Figs 2D, 3A-B); and female medigynium strongly folded ventrally on each side, bearing a short basal stalk, with rounded main plate beneath the basal stalk (Figs 2F, 3C).

Etymology
The specific epithet refers to the bifurcated paramere of the male genitalia.

Male
Head. Head mostly yellow. Rostrum faint yellow, with pair of blackish longitudinal stripes laterally. Maxillary and labial palps yellowish brown, distal segment dark brown. Antenna black brown. Ocellar triangle black ( Fig. 2A).
Thorax. Pronotum yellow, with short black setae along anterior margin and two black longitudinal stripes laterally. Meso-and metanotum pale yellow with black longitudinal stripe on each side. Pleura and sterna yellow. Legs pale brown, distal tarsi dark brown ( Fig. 2A).
Genitalia. Subgenital plate trapezoidal, terminating in ligulate process, covered with long bristles caudally (Fig. 2E). Medigynium strongly folded ventrally on each side, bearing short stalk at base, with round main plate beneath basal stalk. Posterior arm stout, nearly half as long as main plate. Axis concealed in main plate, slightly protruding apically (Figs 2F, 3C).

Diagnosis
This new species can be readily differentiated from its congeners by the following features: wings dusky hyaline, pterostigmal band with broad basal branch, gradually narrowing toward posterior margin, apical band greatly reduced ( Fig. 4A-B); male hypovalve greatly elongated, extending far beyond basal process of gonostylus (Fig. 4H); basal branches of male paramere extremely short, mesal branches semicircular basally and convergent apically, lateral branches curved to dorsal side basally ( Fig. 5A-B); and main plate of female medigynium rounded, folded ventrally into a circular plate (Fig. 5C).

Etymology
The specific name is dedicated to Mr. Zheng-Kun Hu for his generous help to this study.

Male
Head. Head mostly yellow. Rostrum yellow with pair of blackish lateral longitudinal stripes. Maxillary and labial palps yellowish brown, distal segment dark brown. Antenna black. Ocellar triangle black (Fig. 4A, C).
Thorax. Pronotum yellow with several stout setae along anterior margin and two black longitudinal stripes on lateral sides. Meso-and metanotum yellow, with black longitudinal stripe along each side. Pleura pale yellow. Legs brown with tarsomere darkening toward apex (Fig. 4A).

Distribution
Wuling and Miaoling Mountains, Guizhou Province, China (Fig. 1). (updated from Hu et al. 2019c) 1. Wings yellowish with distinct dark brown markings, apical band broad, enclosing a large hyaline window; pterostigmal band complete, with a broad basal branch and a separated narrow distal branch; basal band complete, across the wing or slightly reduced;

Discussion
In this study, we reviewed the descriptions of all the known species of Dicerapanorpa, and found that the so-called D. stotzneri (Esben-Petersen, 1934) in Zhong & Hua (2013) was very likely a misidentification, because the female medigynium differs from the original descriptions (Esben-Petersen 1934;Tjederi 1936;Cheng 1957). The genus Dicerapanorpa was previously known to be restricted to the Hengduan and Qinling-Bashan Mountains. The distribution of D. zhengkuni sp. nov. in the Guizhou Plateau is likely an important biogeographical event. In this case, the genus Dicerapanorpa exhibits an intriguing circular distribution pattern around the Sichuan Basin. The mechanisms of this distribution pattern and associated species diversification in Dicerapanorpa should be an interesting topic to study in the future.