A new velvet ant genus Arkaditilla (Hymenoptera, Mutillidae, Trogaspidiini) from the Oriental Region, with review of species

A new Old World genus in the tribe Trogaspidiini Bischoff, 1920, Arkaditilla gen. nov., is described based on male morphology. Six species are recognized in this genus: A. bagrada (Cameron, 1902), comb. nov. (Indonesia, Malaysia), A. depressicornis (Mickel, 1935), comb. nov. (Malaysia), A. frim sp. nov. (Malaysia), A. gibba sp. nov. (Indonesia), A. leleji sp. nov. (Indonesia), and A. nallinia (Zavattari, 1914), comb. nov. (Indonesia). The species of this new genus were formerly placed in the genus Krombeinidia Lelej, 1996, but they are differentiated from it and other genera by having a unique set of morphological character states, such as the mandible inner margin expanded, forming subbasal tooth; the paramere antero-ventrally serrate; and the digitus dorsal margin lamellate. A key to species of Arkaditilla is provided.


Introduction
The tribe Trogaspidiini Bischoff, 1920 has the greatest species diversity of the four tribes of the subfamily Mutillinae (Pagliano et al. 2020). The eastern Oriental species of this tribe were assigned to the subgenus Trogaspidia Ashmead, 1899 of the New World genus Timulla Ashmead, 1899 by Mickel (1933aMickel ( , b, 1934Mickel ( , 1935, but Invrea (1954) resurrected Trogaspidia to full genus status. Chen (1957) transferred some species of Trogaspidia sensu Mickel to Smicromyrme Thomson, 1870. Lelej (1995, 1996a and Lelej and Yamane (1992) reclassified the Smicromyrme-Trogaspidia assemblage, recognized new genera for species of Smicromyrme sensu Chen, and arranged them in the subtribe Petersenidiina Lelej, 1996. Along with this, East Asian members of Trogaspidia sensu Chen were divided into five genera constituting Trogaspidiina Bischoff, 1920. Those two subtribes were included in Trogaspidiini, but later regarded as separate tribes by Lelej and Nemkov (1997). However, Brothers and Lelej (2017) found that Petersenidiini was a paraphyletic group and synonymized it with Trogaspidiini. Consequently, Trogaspidiini is now represented by 13 genera in the eastern Oriental Region (Brothers and Lelej 2017;Pagliano et al. 2020). The species of this tribe are sometimes difficult to place in those previously established genera, because the "petersenidiine" genera exhibit various intermediate character states between Petersenidiini and Trogaspidiini (Brothers and Lelej 2017). Also, the species of Trogaspidiini show great interspecific morphological variations, making genus delimitation difficult (e.g. Okayasu et al. 2021). Revision of genus-level classification is thus required, and generic placement of described species, which are mostly known from the old literature only (Okayasu et al. 2021), needs to be extensively reviewed.
In this study, I present a review of the Krombeinidia Lelej, 1996 species with male flagellomere 1 depressed, K. depressicornis (Mickel, 1935) and K. nallinia (Zavattari, 1914), because Mickel's (1935) key suggests they are the only species with that trait in the former Petersenidiini. I also examined K. bagrada (Cameron, 1902), which was placed near those two species by Mickel (1935) although it has the flagellomere 1 cylindrical, and three undescribed species that are similar to K. depressicornis and K. nallinia. As discussed below, those "Krombeinidia" species share additional character states that are their potential synapomorphies, so the new genus Arkaditilla is proposed to accommodate them.

Material and methods
The following abbreviations are used to denote institutes housing the material discussed in this study: Specimens were observed under a Leica S8APO stereomicroscope (10-80× magnification). Photo images were taken with a Nikon Digital Sight DS-Fi1 camera attached to a Leica S8APO, and stacked using CombineZM software (Hadley 2008). Measurements of specimens were taken twice, in order to reduce measurement errors, and the mean value was indicated in the description. The distributional maps  were generated using SimpleMappr (Shorthouse 2010). Figures were edited with Adobe Photoshop software and Adobe Illustrator software. Terminology mostly follows the Hymenoptera Anatomy Consortium (2021) for the general morphology, and Harris (1979) for the integument sculpture.
Distribution. Widespread in Sundaland, the Oriental Region (Figs 73-76). Etymology. I am delighted to name this new genus in honor of Arkady Stepanovich Lelej, a fellow mutillidologist, pioneer of Old World mutillid systematics, and friend, to celebrate his 75 th birthday and 50 th anniversary of his career since the publication of Lelej (1971), with a common suffix for mutillid genera. Gender feminine.
Biology. This genus is rare in collections; only twelve specimens of A. bagrada, nine specimens of A. depressicornis, and seven specimens of A. nallinia have been reported by previous authors (Cameron 1902;Zavattari 1914;Mickel 1935Mickel , 1937Lelej 1996b). In this study, however, a series of 28 specimens collected in Malaise traps placed in a lowland rain forest at Pasoh Forest Reserve was examined, suggesting greater abundance in forested habitats. See Maetô et al. (1999) for sampling sites.
Remarks. This new genus belongs to the former Petersenidiini Lelej, 1996 by having the penis valves symmetrical, and the species of this genus were formerly placed in Krombeinidia Lelej, 1996(Lelej 1996a or Petersenidia Lelej, 1992(Lelej 1996b. However, the males of Arkaditilla differ from those of Krombeinidia and Petersenidia by having the mandible with a subbasal inner tooth (mandibular inner margin entire in Krombeinidia and Petersenidia), the basiparamere antero-ventrally serrate (entire in Krombeinidia and Petersenidia), and the digitus dorsal margin lamellate (digitus cylindrical in Krombeinidia and Petersenidia). Within Trogaspidiini, the males of this new genus and Serendibiella Lelej, 2005 share the mandible with subbasal inner tooth, but the former differs from the latter by having the hypostomal carina without a tubercle (present in Serendibiella), the mesocoxa evenly convex (laterally swollen in Serendibiella), S2 without a lateral felt line (present in Serendibiella), S8 flattened (with sublateral longitudinal carina in Serendibiella), and the penis valves symmetrical (right penis valve longer than left in Serendibiella). Arkaditilla bagrada (Cameron, 1902), comb. nov. Figures 1, 2 , 13, 19, 25, 26, 37, 38, 49-51, 67, 73 Mutilla bagrada Cameron, 1902: 76  Identification source. Keyed using Mickel (1935) and compared with the original description. No differences were found between the specimens examined herein and Cameron's description.
Wings well developed; distance between origin of RS on vein SC and base of stigmatic cell equal to stigmatic cell length and first abscissa of RS length; cell 2RS present.
Wings well developed; distance between origin of RS on vein SC and base of stigmatic cell equal to stigmatic cell length and first abscissa of RS length; cell 2RS present.
Remarks. This species and A. nallinia are recognized in Arkaditilla by having the mandible with sharp subapical and large inner subbasal teeth, the mandible ventral margin deeply excised with large basal tooth, the scape ventral carinae divergent apically, F1 strongly depressed, the cuspis widened posteriorly, the digitus posteriorly expanded, the paracuspis tuberculate, and the penis valve weakly expanded ventrally, but the former differs from the latter by having the clypeus strongly elevated even ventrally (clypeus elevated dorsally in A. nallinia), and the cuspis widened near apex (cuspis widened on posterior 1/3 in A. nallinia).
Wings well developed; distance between origin of RS on vein SC and base of stigmatic cell equal to stigmatic cell length and first abscissa of RS length; cell 2RS present.