Journal of Threatened
Taxa | www.threatenedtaxa.org | 26 February 2022 | 14(2): 20631–20636
ISSN 0974-7907
(Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.7765.14.2.20631-20636
#7765 | Received 29
November 2021 | Final received 10 February 2022 | Finally accepted 15 February
2022
Rediscovery of Platerus pilcheri Distant
(Hemiptera: Reduviidae), a forgotten assassin bug
from India, with comments on its range extension
H. Sankararaman
1, Anubhav Agarwal 2, Valérie A. Lemaître 3 & Hemant V. Ghate
4
1 Parasitoid
Taxonomy and Biocontrol laboratory, Department of Entomology, Faculty of
Agriculture, Annamalai University, Chidambaram, Tamil Nadu 608002, India.
2 12 Z Rutland Gate, 4th
street, Aroshree Kailash, Chennai, Tamil Nadu 600006,
India.
3 Department of Life Sciences
(Insects), The Natural History Museum, Cromwell Road, London, SW7 5BD, United
Kingdom.
4 Post-Graduate Research Centre,
Department of Zoology, Modern College of Arts, Science and Commerce
(Autonomous), Shivajinagar, Pune, Maharashtra 411005, India.
1 sankararaman05@gmail.com
(corresponding author), 2 anubhavpost@gmail.com, 3 v.lemaitre@nhm.ac.uk,
4 hemantghate@gmail.com
Editor: Anonymity requested. Date of publication: 26 February 2022 (online
& print)
Citation: Sankararaman, H., A.
Agarwal, V.A. Lemaître & H.V. Ghate
(2022). Rediscovery of Platerus pilcheri Distant
(Hemiptera: Reduviidae), a forgotten assassin bug
from India, with comments on its range extension. Journal of Threatened Taxa 14(2): 20631–20636. https://doi.org/10.11609/jott.7765.14.2.20631-20636
Copyright: © Sankararaman et al. 2022. Creative Commons Attribution 4.0
International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: HS obtained travel funds through DST PURSE phase II of Annamalai University.
Competing interests: The authors declare no competing interests.
Acknowledgements: We thank Mick Webb (BMNH, UK),
Tadashi Ishikawa (Tokyo University of Agriculture, Japan) and H.M. Yeshwanth
(University of Agricultural Sciences, GKVK, Bengaluru, India) for kindly
providing images of (type) specimens. We also extend our thanks to Kolla Sreedevi (National Bureau
of Agricultural Insect Resources, Bengaluru) for providing relevant literature
on P. bhavanii. HS is grateful to S. Manickavasagam. HVG is indebted to the authorities of
Modern College for providing facilities and encouragement.
Abstract: 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.
Keywords: Harpactorinae, Nagusta,
Nagustoides, Oriental region, China.
A single male harpactorine
assassin bug was carefully studied and photographed in the Talle
Valley Wildlife Sanctuary (Ziro, Arunachal Pradesh),
in September 2019. It showed the main diagnostic characters of the genus Platerus 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, 1904; Zhao et al. 2006b). It was subsequently
identified as P. pilcheri Distant, 1903 based
on the original description and an illustration provided by Distant (1903,
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 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 and P.
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.
Taxonomy
Reduviidae Latreille,
1807
Harpactorinae Amyot
& Serville, 1843
Platerus Distant, 1903
Platerus Distant, 1903: 247 (type species
Platerus pilcheri,
by monotypy); Maldonado Capriles
1990: 258; Ambrose 2006: 2399; Zhao et al. 2006b: 25; Biswas et al.
1994: 398; Biswas & Mitra 2014: 14; Bhagyasree 2017: 67.
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.
Platerus pilcheri Distant, 1903 (Image 1 & 2)
Platerus pilcheri Distant, 1903: 248, 1904: 375;
Maldonado Capriles 1990: 258 (catalogued); Ambrose
2006: 2399 (in checklist); Zhao et al. 2006b: 25 (redescription,
key, description of female); Biswas et
al. 1994: 398 (listed); Biswas & Mitra 2014: 14
(checklist, misspelling: P. pilchen); Bhagyasree 2017: 67 (as type species of Platerus,
similar misspelling).
Material studied
1 male, India, Arunachal Pradesh,
Ziro (Image 1); specimen not collected.
Other material for which images
are provided:
Type material. Syntype, male,
India, Sikkim, with the following labels: red-bordered “Type” disc; “♂”; “Platerus pilcheri
Dist.”[Distant’s handwriting]; “Sikkim/ 7000 [ft]/
June 1895/ J.G. Pilcher // 97/ 120”; “BMNH(E) 1255121”; “NHMUK 013588826” (BMNH) (Image 2).
Additional material: (known from the literature /
examined in the BMNH)
1 male, India, West Bengal, Jalpaiguri, with the following labels: “♂”, “Gopaldhara, Bw./
Darjeeling./ 4,720 ft. 29.ix.14./ H. Stevens.”, “At light.”, “NHMUK 013588827”
(BMNH); “1 ex., Darjiling, Brich
hills.,? coll. M. Banerjee; 2 exs., Darjiling, vii.1912, coll.?” (ZSI, fide Biswas et al.,
1994, not seen); 1 female, China, Yunnan: Dulong Valley, with the following
labels: “♀”, “Upper Burma:/ Taron Valley./
16.x.1938./ R. Kaulback./ B.M.1938-741.”, “Alt.5,000
ft./ lat.N.28° 08’/ Long. E 98° 20’.”, “NHMUK 013588828” (BMNH) (Although one
label reads ‘Upper Burma’, i.e., northern Myanmar, the coordinates on another
label indicate a locality in China; this
may be explained by the instability of the Burma-Yunnan frontier (see McGrath
2003). Ronald Kaulback trekked in Tibet (see Kaulback 1934) and “Tibet” is what was recorded in the BMNH
accession register under entry 1938-741, when he presented the specimen to the
BMNH in December 1938); 1 female, China, Xizang (Tibet), “Motuo; 29-viii-2003, collector unknown; kept in CAU [China Agricultural University, Beijing]”
(fide Zhao et al. 2006b, not seen); A further two males, without any data, are
deposited in the BMNH.
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 (1903, 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.
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 7th 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 5th 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.
Distribution: China (Xizang, Yunnan), India
(Sikkim, West Bengal, Arunachal Pradesh).
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 Pradesh, while specimens found in the collections of ZSI and BMNH
allow us to add to the distribution West Bengal and the Yunnan province of
China (Image 4), altogether showing the northward and eastward extension of the
range of this species. No specimens were collected during the present study.
The species was diagnosed based on the original description and subsequent
illustrations.
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