Sinothereva, Winterton, 2020

Winterton, Shaun L., 2020, A new bee-mimicking stiletto fly (Therevidae) from China discovered on iNaturalist, Zootaxa 4816 (3), pp. 361-369 : 362-363

Sinothereva gen. n.

( Figs 1–7 )

( urn:lsid:zoobank.org:act:0EF353E5-A066-431A-8981-091E8B2235B5 )

Type species. Sinothereva shangui sp. n., herein designated.

Diagnosis. Flagellum turbinate, shorter than combined scape and pedicel length; scape slightly thicker than pedicel and flagellum; frontal part of head (male) flat, frons only slightly produced anterior to eye; head length and height sub-equal; male frons width (at narrowest point) wider than ocellar tubercle; parafacial without setae; male occiput with scattered postocular macrosetae admixed with numerous finer setae, row of macrosetae along postocular ridge also distinct; central depression of prosternum setose; postspiracular setae present on metanepisternum; posterior surface of midcoxa setose; hind coxal knob absent; femoral vestiture as dense, erect filiform setae admixed with adpressed, scale-like setae; fore- and midfemoral anteroventral (av) macrosetae present, posteroventral (pv) and dorsocentral macrosetae absent; hind femur with series of anteroventral (av) setae along segment, posteroventral (pv) macrosetae present as short sub-apical series; hind femur and tibia longer than in fore and midlegs; scutal chaetotaxy (pairs of macrosetae): supra-alar macrosetae: 1, post alar macrosetae: 1, dorsocentral macrosetae: 0, scutellar macrosetae: 0; wing costal wing vein circumambient around wing margin; vein R 1 with setulae absent; cell m 3 open, veins M 3 and M 4 separate to margin; male terminalia with dorsal apodeme of parameral sheath broad, covering aedeagus dorsally; distiphallus directed ventrally; ventral apodeme as a single lobe, narrow; gonocoxite with posterior projections present ventrally, but greatly reduced, posteromedial margins proximal, ventral lobe round; gonocoxal process (igp) present, articulated. Female unknown.

Included species. Sinothereva shangui sp. n.

Comments. This new genus is known only from two male specimens from mid-elevations in Northern China, one was collected by the author and represents the holotype specimen. The second individual that was in much better condition is known only from a series of high quality photographs taken in the field ( Figs 1–3 ) by the nature photographer, Shan Gui. The specimen was not collected. These images were posted to iNaturalist for subsequent community-based identification. It was here through serendipity, that the author first discovered this distinctive new stiletto fly; it was subsequently compared with the previously collected specimen (but in poor condition) from the same region and confirmed as the same species .

This new genus and species is a member of Therevinae although it is not clear to which genus group it belongs. The most important and immediately diagnostic features of Sinothereva gen. n. are the lack of scutellar macrosetae, the male frons much wider than the ocellar tubercle, and absence of both parafacial setae and the hind coxal knob. Also distinctive is the extensive setal pile on the entire body, including the head and femora. Some of these characteristics can also be found in Aristothereva , but Sinothereva gen. n. can be differentiated by the very small and narrow arista (large and conical in Aristothereva ), lack of scutellar macrosetae (numerous in some Aristothereva ) and in the male genitalia by the reduced posteriorly directed processes on the gonocoxites (well-developed in Aristothereva ). Indeed, Sinothereva shows considerable affinity for Aristothereva and these two Palaearctic genera are likely closely related. Broader relationships of Sinothereva gen. n. (and Aristothereva ) to other therevine genera are less clear. Morphological synapomorphies uniting members of either the Thereva or Pandivirilia genus groups are not well defined (see Holston et al., 2007; Winterton et al., 2016), and Sinothereva gen. n. and Aristothereva exhibit characteristics of both. Neotherevella Lyneborg appears to be related to Aristothereva and Sinothereva gen. n. and is found in the Palaearctic and Afrotropical regions. Neotherevella has a similar habitus with extensive erect whitish to silvery setal pile, male frons usually wider than the ocellar tubercle and parafacial setae absent, amongst other features. In contrast with Sinothereva gen. n., both Neotherevella and Aristothereva have scutellar macrosetae present. Holston et al. (2007) considered Aristothereva and Neotherevella as part of the Pandivirilia genus group, although these genera were not sampled in any of the published phylogenetic analyses to confirm this hypothesis ( Holston et al., 2007; Winterton et al., 2016).

The lack of a hind coxal knob is exceedingly rare in Therevidae , being absent only in a few species in the genera Anabarhynchus , Actorthia Kröber , Ammonaios and Arenigena Irwin & Lyneborg ( Hauser & Irwin, 2003; Winterton, 2004). The apparent distant relationship amongst many of these genera suggests that loss of the hind coxal knob has occurred multiple times.

Remarkably, while wasp mimicry is found in other stiletto flies, it typically takes the form of mimicking pompilid or sphecid wasps (e.g. Agapophytus Guerin ). Sinothereva shangui sp. n. is the first example of a stiletto fly that apparently mimics bees ( Apidae ), resembling species of bumble bees in the genus Bombus L. Indeed , this new stiletto fly is very similar to species such as Bombus sibiricus (Fabricius) or Bombus hypnorum (L.), which are also found in the same area. Still, while the erect vestiture and bee-like mimicking appearance is distinctive for Sinothereva shangui sp. n., it is possible that these features are species-specific and not characteristic of the genus. Only when more species are discovered, may the full extent of such mimicry in Sinothereva gen. n. be known.

Figures

FIGURE 1. Sinothereva shangui gen. et sp. n., male, photographed in the field, Xinglong, China (Photograph copyright: Shan Gui). (Link: https://www.inaturalist.org/photos/54918804)

FIGURE 2. Sinothereva shangui gen. et sp. n., male, photographed in the field, Xinglong, China (Photograph copyright: Shan Gui). (Link: https://www.inaturalist.org/photos/54918833)

FIGURE 3. Sinothereva shangui gen. et sp. n., male, photographed in the field, Xinglong, China (Photograph copyright: Shan Gui). (Link: https://www.inaturalist.org/photos/54919032)