Rediscovery of Platerus pilcheri Distant (Hemiptera: Reduviidae), a forgotten assassin bug from India, with comments on its range extension

: Platerus pilcheri Distant , 1903, a harpactorine reduviid, is rediscovered from India after more than a century since its original description. A brief diagnosis of this species, a note on its range extension, a distributional map, and images of live habitus are provided along with the images of a syntype preserved in the Natural History Museum, London (BMNH). We also present a comparison with the other Indian congeneric species, Platerus bhavanii Livingstone & Ravichandran, 1991, and show that this latter species does not belong in the genus Platerus and is to be treated as species inquirenda . The issue of the subsequent documentation of Platerus bhavanii from Karnataka is also discussed.

ISSN 0974-7907 (Online); ISSN 0974-7893 (Print)  Distant, 1903, viz., the head about as long as the pronotum; a long oblique suberect spine at the base of the antenna; a posterior pronotal lobe with two long, discal, tuberculous, erect, acute spines and lateral pronotal angles spinously produced (Distant 1903(Distant , 1904Zhao et al. 2006b). It was subsequently identified as P. pilcheri Distant, 1903 based on the original description and an illustration provided by Distant (1903Distant ( , 1904, as well as the redescription, illustrations and key provided by Zhao et al. (2006b). A further comparison with images of a male syntype of Platerus pilcheri, preserved in the BMNH, confirmed the identity of the bug photographed in Arunachal Pradesh.
Platerus Distant, 1903 is a small genus in Reduviidae (Hemiptera), with only three species, all described from the Oriental region (Zhao et al. 2006b). Distant (1903) established Platerus with P. pilcheri as the only species, based on an unspecified number of male specimens, collected by J.G. Pilcher in Sikhim [= Sikkim], India; later Distant (1904) included this genus in Harpactorinae, division Euagorasaria and also provided a figure of the dorsal habitus of this species. While Distant's 'divisions' of Harpactorinae are no longer used, Distant (1904) still proves useful for the identification of the Indian

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hemipteran fauna. The division Euagorasaria has been merged in the tribe Harpactorini, which includes species with a curved labium. The subfamily Harpactorinae is the largest reduviid subfamily, with over 300 genera and more than 2,800 species (Schuh & Weirauch 2020).
The other two species of the genus Platerus, viz., P. bhavanii Livingstone &Ravichandran, 1991 andP. tenuicorpus Zhao, Yang &Cai, 2006 are known from India and China (Tibet), respectively. Platerus pilcheri has never been documented in detail from any part of India since its original description, although it has been collected, as can be vouched by specimens in the collections of the BMNH (see 'Material studied') and the Zoological Survey of India (ZSI, see Biswas et al. (1994)). More recently, one female specimen was reported from Xizang (Tibet), China, by Zhao et al. (2006b), who described the female of the species for the first time. Agarwal (2019) made images of a specimen available on the iNaturalist website; this was recently identified as P. pilcheri. The present report is based on this sighting made on 7 September 2019 at the Talle Valley Wildlife Sanctuary, Arunachal Pradesh (27.545614N & 93.830229E). The specimen was studied in detail and released back into nature; no collections were permitted in that area during the study.
Since the genus and the species have been originally, and subsequently, described in detail, we are here only presenting recent images of this species with brief comments on the other Indian congeneric species, P. bhavanii. We are also providing images of a syntype of P. pilcheri and documenting other specimens deposited in the BMNH.

Diagnosis
Division Euagorasaria, sensu Distant (1904), which includes the genus Platerus, is characterized by an elongate body, the head with a distinct tubercle or spine behind the base of each antenna and lateral pronotal angles spinous or at least prominent. Within Euagorasaria the genus Platerus is diagnosed by the following characters: anterior tibia not curved at the tip and without a spine, anterior lobe of pronotum without any prominent tubercles at the sides, the posterior lobe of pronotum with discal spines and the head about as long as the pronotum.

Diagnostic characters of the genus
The genus Platerus has been described thoroughly by Distant (1903) and some more details were added by Zhao et al. (2006b); for this reason, we do not reiterate those characters. Only some characters that are relevant for the subsequent discussion are given below: Head long, about or almost as long as the pronotum, postocular portion a little longer and slenderer than the anteocular portion; pronotum subtriangular, the anterior lobe obsoletely tuberculate, its anterior angles moderately prominent, its posterior area profoundly and broadly sulcate; abdomen long, scarcely wider than the hemelytra, the fifth [visible] segment a little dilated on each side.

Brief description
Coloration: Body dorsally mostly black with symmetrical pattern of white markings on pronotum and corium. Antennae and legs with alternate black and yellow annulations. Anterior pronotal lobe, discal and lateral spines of posterior lobe black; a white fine marking on lateral margins of anterior lobe of pronotum continued as a wavy 'W'-like transverse fascia on posterior lobe, just in front of discal spines. Three broad black annulations on all femora are also clearly visible; clavus entirely black, membrane fuliginous with basal half partly brownish-black, apical half pale hyaline; conspicuous white reticulate markings on corium (Image 1a). Apical segment of labium, fine tibial annulations and connexival coloration black, showing a well-defined black anterior part of each abdominal segment (Image 1b) Structure: Head about as long as pronotum, with long, anterolaterally directed spine at base of antenna. First visible labial segment longer, slightly passing posterior border of eye and longer than second. Pronotum with the anterior lobe short, posterior lobe more than twice as long as anterior lobe; lateral pronotal angles spinously produced, their posterior margin distinctly notched near base; posterior pronotal lobe with discal, long erect, tuberculous spines; fore femur slightly incrassate; abdomen with sixth connexival segment dilated laterally (Image 1a,b).

Remarks
Validity of our identification: The single male from Ziro, Arunachal Pradesh, exactly matches the original description and the subsequent habitus figure given by Distant (1903Distant ( , 1904, as well as the syntype of P. pilcheri preserved in the BMNH, as can be seen from the images provided (Image 2). This species can also be identified, according to the recent key in Zhao et al. (2006b).
Platerus bhavanii does not belong in Platerus: P. pilcheri was the only species known under this genus until Livingstone & Ravichandran (1991) described a new species Platerus bhavanii Livingstone & Ravichandran, 1991, collected from the Botanical Garden near Bhavani Dam, Periyar, Tamil Nadu, southern India. The specimens examined by them included one female (holotype), one male and another female (paratypes); our attempts at locating these types and obtaining images remained unsuccessful. The authors gave a brief description and only a dorsal habitus line drawing, without any information on male / female genitalia. Considering the description and illustration given by Livingstone & Ravichandran (1991), it is important to point out here that P. bhavanii has some characters that are distinctly different from the original diagnostic characters of the genus Platerus given above. For example: (i) the pronotum is of a very different shape in P. bhavanii, (ii) the broadly sulcate area in the posterior part of the anterior lobe described in the genus Platerus is neither mentioned in the original description of P. bhavanii nor visible on the line drawing provided and (iii) in Platerus, only abdominal segment V is dilated on either side, as per Distant (1903), while in P. bhavanii segments V to VII are dilated (Distant (1903) had stated: 'the fifth segment a little dilated on each side'; this must refer to a visible segment V, i.e., segment VI, as Zhao et al. (2006b) have described the sixth connexival segment as expanded in the female and our specimens show expansion on the sixth connexival segment). Finally, Livingstone & Ravichandran (1991), while describing P. bhavanii, had stated: "…anteocular area with a median 'Y'-shaped, smooth brown streak, posteriorly confluent with the transverse fissure connecting the eyes"; this character is not found in the genus Platerus.
Because of these differences alone we strongly reckon that P. bhavanii does not belong in the genus Platerus and that the type material must be re-examined to settle its identity. We therefore suggest that until the types are located, the species P. bhavanii should be treated as species inquirenda, i.e., a species of doubtful identity.
Specimens identified as P. bhavanii may not be this species and do not belong in Platerus: Bhagyasree (2017) examined seven females collected from various parts of Karnataka, identified those as Platerus bhavanii and photographically illustrated one of them. Looking at the original line drawing in Livingstone & Ravichandran (1991) and the photo provided by Bhagyasree (2017), it seems that the specimens in Karnataka are again different and a detailed re-examination of these specimens is essential. It is certain that Bhagyasree's specimen, photographed anew for this study (Image 3), does not belong in Platerus either as it also lacks the diagnostic characters of the genus Platerus; in addition, a lateral view of the head of this specimen shows the first visible segment of the labium to be passing much beyond the posterior border of the eye (Image 3b,c), a feature not seen in the similar view of the live specimen (Image 1b) or of the syntype (Image 2b) of P. pilcheri. In the absence of the type material of P. bhavanii, it is also difficult to tell with certainty if Bhagyasree's specimens are conspecific with what was originally described as P. bhavanii.

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P. bhavanii and specimens identified as such could belong to either Nagustoides or Nagusta: Some of the aforementioned characters that preclude P. bhavanii and specimens identified as such by Bhagyasree (2017) to be placed in Platerus are, however, seen in the genera Nagustoides and Nagusta: (i) the 'Y'-shaped smooth brown streak and more than one expanded abdominal segments are seen in the genus Nagustoides Miller, 1954(Miller 1954 (Fig. 43 A); Zhao et al. 2006a (Fig. 1); Ishikawa & Naka 2016 (Fig. 3)) although, in Nagustoides, only abdominal segments (connexivum) V and VI are laterally expanded (and the external apical angle of segment V is spinous) and the 7 th abdominal sternite has only a small median spine on the posterior border. In some species of Nagusta Stål, 1859, one or more abdominal segments are expanded or dilated as well (Villiers 1967). (ii) the first visible segment of the labium is passing much beyond the posterior margin of the eye in Bhagyasree's P. bhavanii (Image 3b,c), which is another character seen in the genera Nagusta and Nagustoides (as a matter of fact, in Nagustoides, the first visible labial segment is longer than the second and third combined; this is one of the characters that separates it from the genus Nagusta Miller, 1954). For these reasons, we suspect that the originally described P. bhavanii and the specimens identified as P. bhavanii by Bhagyasree (2017) possibly belong in either Nagusta or Nagustoides and certainly not in Platerus. Miller (1954: 52) separated Nagustoides from Nagusta thus: "Allied to Nagusta Stål, [...] but it differs in having the basal segment of the rostrum longer than the remaining segments together, the anterior pronotal lobe tuberculate, the posterior lobe without subdorsal spines or gibbosities and the expanded 5 th connexival segment spinous". Despite this, subsequent papers have illustrated Nagustoides with discal tubercles on the posterior lobe of pronotum (Zhao et al. 2006a;Ishikawa & Naka 2016), a character seen in Bhagyasree's specimens, and, even described in P. bhavanii. To better define Nagusta and Nagustoides a detailed study of their types species need to be carried out.
Thus, we firmly state that our discovery of P. pilcheri in Arunachal Pradesh becomes the first authentic record of this genus and species from India, after a gap of over 100 years. This discovery also indicates that this handsome predatory bug is still inhabiting northeastern India. Besides this, we also maintain that Platerus pilcheri is the only species under the genus Platerus in India; the other described species from India is of doubtful identity.
Distant's historical record of P. pilcheri was from Sikkim, Zhao et al. (2006b) reported it from Xizang (Tibet), China, the present record is from Ziro, Arunachal www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.