Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 March 2021 | 13(3): 17939–17949
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.6285.13.3.17939-17949
#6285 | Received 10 June 2020 | Final
received 05 March 2020 | Finally accepted 07 March 2020
A new taxon of Nacaduba Moore, 1881 (Lepidoptera: Lycaenidae: Polyommatini)
from Agasthyamalais of the Western Ghats, India
Kalesh Sadasivan
1, Baiju Kochunarayanan
2, Rahul Khot 3 & S. Ramasamy Kamaya Naicker 4
1,2 Travancore Nature History
Society, MBRRA 65, Jyothis, Mathrubumi
Road, Vanchiyoor, Thiruvananthapuram, Kerala 695035,
India.
3 Bombay Natural History Society,
Hornbill House, S.B.S. Road, Fort, Mumbai, Maharashtra 400001, India.
4 Palace, Saptur
Post, Peraiyur Taluk, Madurai, Tamil Nadu
625705, India.
1 kaleshs2002in@gmail.com
(corresponding author), 2 baijupaluvally@gmail.com, 3 r.khot@bnhs.org,
4 srknaicker@gmail.com
ZooBank: urn:lsid:zoobank.org:pub:EB6EB702-006A-4F44-BAE3-1BEAAFF0F8DA
Editor: George Mathew, Mavelikara, Kerala, India. Date
of publication: 26 March 2021 (online & print)
Citation: Sadasivan,
K., B. Kochunarayanan, F. Khot
& R.K. Naicker (2021). A new taxon of Nacaduba Moore, 1881 (Lepidoptera: Lycaenidae: Polyommatini) from Agasthyamalais of the Western Ghats, India. Journal of Threatened Taxa 13(3): 17939–17949. https://doi.org/10.11609/jott.6285.13.3.17939-17949
Copyright: © Sadasivan
et al. 2021. 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: None.
Competing interests: The authors
declare no competing interests.
Author details: Kalesh Sadasivan: A plastic surgeon by
profession and a naturalist by passion, from Kerala. Founder member and
research sssociate of Travancore Nature History
Society (TNHS), an NGO based in Trivandrum since 2010. A wildlife photographer
and an amateur taxonomist with specific interest in invertebrates. Discovered
and described more than a dozen new species to science from the Western Ghats
including frogs, reptiles, wasps, ants & odonates.
Baiju Kochunarayanan: A
school teacher by profession, research associate of Travancore Nature History
Society (TNHS), an NGO based in Trivandrum since 2010. Interested in
butterflies and invertebrates of Western Ghats. A wildlife photographer working
on documentation of early stages of lepidoptera. Rahul Khot: Currently
working as Assistant Director (Natural History Collection) in BNHS, Mumbai,
India. His research interests include insect taxonomy, biological collection
management, urban ecology, citizen science, bird hazard to aircraft studies,
and long-term ecological monitoring. He is working as Principal Investigator
for various BNHS Projects. Sundara Ramasamy Kamaya Naicker A farmer
by profession, a birder and an avid butterfly enthusiast whose persistent
efforts led to the discovery of this new species. An active member of Vanam an NGO, based in Theni, working in varied landscapes
of Western Ghats of Tamilnadu.
Author contribution: KS—discovered the lifecycle,
photographed and dissected the species for confirmation. BK—reared and
documented the lifecycle. RK—manuscript
revision and taxonomic comparison with related species. SRKN—reared and
documented the lifecycle, Manuscript revision.
Acknowledgements: We thank George van der Poorten, Nancy van der Poorten, Krushnamegh Kunte, and Ben Price
for their advice and help with reference materials. Satya Krishna Prakash for digitalisation of
the hand drawn illustrations; Mr. Kandaswamy for his
hospitality and permission to access the hostplant in his private estate at Thenkasi, Tirunelveli, Tamil Nadu to photograph the
insect. We would like to thank Deepak Apte, ex-director BNHS for his support. We would like to thank Ashok Sengupta, Dipendra Nath Basu, Preeti Y, Anila VM for their help
with the manuscript. We are grateful to
members of Travancore Nature History Society, Thiruvananthapuram for their help
in field.
Abstract: A new butterfly taxon, Nacaduba sinhala ramaswamii ssp. nov.
(Lepidoptera: Lycaenidae: Polyommatini),
is described from Agasthyamalais of southern
Western Ghats in peninsular India. The
new taxa can be diagnosed from all other Nacaduba
of southern India and N. sinhala
Ormiston, 1924 from Sri Lanka, by its
distinct male genitalia. The early
stages, larval hostplants, flight periods, ecology and the known distribution
of the new taxa are discussed. The
revised keys to all known Nacaduba of Western
Ghats of peninsular India are provided.
Keywords: Butterfly, distribution,
ecology, genitalia, Kerala, larval host plants, new taxa, subspecies.
Introduction
Line blues are small butterflies belonging to the
subfamily Lycaenidae; essentially Indo-Australian in
distribution (Corbet 1938). Their
distribution ranges from India and Sri Lanka, to the whole of southeastern Asia, Australia, and Samoa. They are characterised by hairy eyes,
anastomosis of veins 11 and 12 on forewings, male wings with purple gloss on
the upperside, and underside of both sexes with dull
whitish striae.
Males of all species have battledore-shaped specialised androconial scales and some species have long ribbon scales
on the upperside of wings that gives them a frosted
look (Corbet & Pendlebury 1992).
Line blues are broadly classified according to the
number of lines or bands seen in the underside of the forewing as four-line
blues and six-line blues. Evans (1932)
considered all line blues under the genus Nacaduba
Moore, 1881. But according to the
present taxonomic placements following Tite (1963),
the old genus has been split into several genera under Prosotas
Druce, 1891, Petrelaea
Toxopeus, 1929, and Ionolyce
Toxopeus, 1929, in addition to Nacaduba. Prosotas differs from Nacaduba
by being smaller, having hindwing spaces between the striae
more or less darkened, and the valva (claspers) of
males being simple and ending in a long incurved point. Prosotas may
or may not be tailed while Nacaduba are always
with the tail on the hindwing (Corbet & Pendlebury 1992). The genus Prosotas
has three species in peninsular India, namely: Common Line Blue Prosotas nora ardates
(Moore, [1875]), Tailess Line Blue Prosotas dubiosa indica (Evans, [1925]), and White-tipped Line Blue Prosotas noreia hampsonii (de Nicéville,
1885). The genus Petrelaea
and Ionolyce have one species each,
namely, Dingy Line Blue Petrelaea
dana (de Nicéville, [1884]) and Pointed Line Blue
Ionolyce helicon viola (Moore,
1877) in peninsular India.
The Nacaduba males
are dark blue or violet above, while females are paler or white with dark
border on the upperside; and the underside of both
sexes are brownish to grey with linear parallel white lines (Evans 1932). At present, eight species of the genus Nacaduba
are recorded in peninsular India. This
includes two species of four-line blues, viz., Large 4-line Blue (Nacaduba pactolus continentalis Fruhstorfer,
1916) and Pale 4-line Blue (N. hermus
sidoma Fruhstorfer,
1916) as well as four species of six-line blues, viz., Trasparent
6-line Blue (N. kurava canaraica Toxopeus, 1927),
Opaque 6-line Blue (N. beroe gythion Fruhstorfer, 1916),
Rounded 6-line Blue (N. berenice plumbeomicans (Wood-Mason & de Niceville, 1881)),
and Dark Ceylon 6-line Blue (N. calauria
evansi Toxopeus, 1927)
(Larsen, 1987). Nacaduba
calauria evansi Toxopeus, 1927 and N. berenice
plumbeomicans (Wood-Mason & de Niceville,
1881) were the two taxa that were only added later to southern Indian fauna
from Nilgiris by Larsen (1987). The keys to the Indian forms of Nacaduba were given by Evans (1932), which are still
being followed, except for the 4-line blues, whose markings lend themselves for
easy identification, others of the genus need an examination of male genitalia
for species confirmation (Corbet 1938).
Ribbon scales in males are helpful in narrowing down the species, and
these are absent in N. kurava canaraica Toxopeus and N.
calauria evansi Toxopeus (Corbet & Pendlebury 1992).
Two individuals of Nacaduba
line blues were photographed in October 2011 from Bonaccord
Estate and later in September 2013 from a homestead in Vithura
in Thiruvananthapuram District of southern Kerala, by the first author. These individuals were paler in coloration in
comparison to the other Nacaduba line blues
that were mud-puddling with them on a damp patch on the ground. Similar pale coloured individuals were also
observed and photographed at Rosemala, Thenmalai in January 2018, and Thenkasi
in Tamil Nadu in October 2018. A few
days later in the same month, a Nacaduba
female was observed ovipositing on young sprouting
leaves from the cut stem of Dimocarpus longan Lour. (Sapindaceae)
sapling, in Vithura (Fig. 1). Further investigation of the leaves revealed
early stages of the Nacaduba species in
different stages from egg to final instar larvae. These larvae were reared and details of the
adults noted. The dissection of
genitalia of male specimens were done and they were unlike any known Nacaduba from southern India and on further
investigation they were found matching the Sri Lankan species Nacaduba sinhala
Ormiston, 1924. The adults, early stages
and larval host plant were similar to the Sri Lankan taxon, but the genitalia
of the males were structurally different from it. This is the first confirmed record of this
taxa occurring in the Western Ghats and thus the Indian mainland. We describe here the early stages and ecology
of the taxa as well as provide a modified key to all known Nacaduba
of the Western Ghats in peninsular India.
Materials and Methods
The larvae of Nacaduba
were raised on the leaves of its natural host plant Dimocarpus
longan Lour. (Sapindaceae)
under laboratory conditions and the details of each stage noted. The eclosed
butterflies were studied. Taxonomy of Nacaduba follows Tite
(1963). Identification of species
follows Ormiston (1924), Evans (1932), Woodhouse (1947), and van der Poorten & van der Poorten (2018). Genitalia and external morphology were
compared with specimens of Nacaduba sinhala Ormiston 1924, in the Ormiston’s collection
from Sri Lanka, housed in Bombay Natural History Society (BNHS), Mumbai,
India. The genitalia were studied by
soaking overnight in KOH, then dissected under Stereo-zoom microscope (HEADZ
Model HD81) and preserved in glycerol.
Illustrations were drawn by the first author using the Stereo-zoom
microscope. The length of the forewing
(FW) is measured as the longest straight-line distance from the wing base to
the wing tip following Van hook et al. (2012).
Terminology for wing patterns follows Evans (1932) and genitalia
descriptions follow Corbet & Pendlebury (1992). Holotype and four paratypes are deposited
in the insect collection of National Centre for Biological Sciences (NCBS),
Bengaluru; other paratypes will be subsequently deposited in Zoological Survey
of India (ZSI), Kozhikode and Bombay Natural History Society (BNHS), Mumbai.
Results
Nacaduba sinhala ramaswamii Sadasivan ssp. nov.
(Image 1A,B; Figure 2E)
urn:lsid:zoobank.org:act:037ED0C6-64F3-4D5C-94A9-EEA924C8E8B3
Materials examined (n= 5, 3
males and 2 females)
Holotype (Image
1A&B): NCBS-BH870, September 2018, male, Vithura
(8.676N, 77.095E), Thiruvananthapuram District, Kerala, India, at 100m, both
ex. larvae on Dimocarpus longan Lour. (Sapindaceae), coll. Kalesh Sadasivan.
Paratypes/Allotypes: NCBS-BH871 and NCBS-BH872, both males, bearing the
same data as the holotype NCBS-BH870.
NCBS-BH873 (Image 1C&D) and NCBS-BH874, both females, bearing the
same data as the holotype NCBS-BH870.
Additional field records (Image 4)
Two male specimens were observed and photographed in
the field by the authors from Rosemala, Shendurney Wildlife Sanctuary, Kollam District, Kerala
State, India, January 2018, at 100m, from a habitation near secondary forest.
Four male specimens and three female specimens were
observed and photographed in the field by the authors from a private estate
plantation, Tenkasi, in October 2018.
One male specimen and one female specimen were
observed in the field by Kalesh Sadasivan
from Bonaccord Estate, Peppara
Wildlife Sanctuary, Trivandrum District, Kerala State, India, October 2011 at
100m, from a habitation near secondary forest.
Description (Image 1A&B)
Male
Forewing length 14mm (n= 2). Antennae black checkered in jet black and
white on the underside, apiculus white spotted on the
lateral aspect; eyes black; palpal bases white
haired, rest is greyish and tips black; legs vertically streaked in black and
white, tarsus checkered in black and white; whole thorax dorsally covered in
pale violet blue hairs laterally almost white above the origins of the wings,
the hairs extending into the proximal abdominal segments; thorax underside
clothed in white hairs; abdomen with shorter greyish-violet hairs on dorsum,
underside paler, almost whitish, and the tip of the abdomen paler; hindwings
tailed, tails black, tipped with white and with a brownish area in between them
almost as wide as the white tip. Termen and tornus rounded more so in hindwing.
Upperside: General color
is pale violet-blue with the central areas of both wings transparent and
showing the bands on the underside. The
whole wing surface is smeared in battledore androconial
scales and long narrow ribbon scales, the latter giving a frosted look in
photographs (Image 1A).
UpF: Upperside
violet-blue; the underside forewing markings showing on upperside
in males, especially in the discal and post discal regions. The
transparent regions of wings more of brownish.
Basal areas of wings: sub-marginal areas are more opaque with iridescent
pale violet scales. Long pale
bluish-violet hairs along vein 1a and dorsal margin (a continuation of the
paler cilia), which may be lost in older individuals. A very thin marginal line brownish-black and
this colour extends as short black streaks along all
the veins reaching the proximal sub-marginal region. Cilia dark grey, turning paler at the tonus
and dorsum. UpH: The general scheme is as in the forewing,
with discal and post discal
regions transparent and the underside bands showing through; basal,
sub-marginal areas are opaque and clothed in iridescent violet scales. Marginal line
black and extending though the veins into the sub-marginal region. Cilia dark greyish-brown, turning paler
basally after the tornus and apex. Space
1a is ashy in the basal region and turning into brownish towards the
tornus. The basal region, cell and the
space 1b is clothed in very long pale violet blue hairs. Tornal region is darker at the areas of
reflection of the tornal spots on the underside (Image 1A).
Underside: Generally pale brownish-grey with the basal, discal and post discal broad
prominent bands on both wings, these bands appearing crowded in the post-discal region of the hindwing; a sub-marginal series of
almost heart-shaped greyish-brown spots basally and apically white bordered;
and a marginal series of streaks of the same color capped with thin white
marginal line and the thin dark marginal line.
Three tornal spots on hindwing in spaces 2, 1a and 1b. UnF: The usual
series of basal, discal and post discal
bands, bounded by broad white streaks on either sides and grey on the inner
side. The basal band is unbroken and
extends from 1b-outer vein of the cell, and represented by a spot there after
near the leading margin of the wing. The
discal band is broken and a segment is seen in the
cell and its distal continuation is broken into two parts; one part in space 7
is shifted outwards, lying between the discal and
post-discal band; while the second part in space 8 is
in line with the band. Segments of discal band in 1c and 2 are continuous and lies between the
segment in outer cell and the postal discal band,
thus making a ‘Y’ formation with them, though disjunct from distal cell
band. The post-discal
band is a zig-zag stack of parts in spaces 3–6, though more or less in
continuity. The sub-marginal series of
large heart-shaped dark grey spots spaces 2–6, whose sharp apices are directed
towards the wing bases in spaces 1b-6.
Marginal series of flattened crescentic dark grey spots from 1b-6. A thin inner marginal line of white from
tornus to apex made of a series of thin curved lines in each space, fading
after space 6. Another marginal line of
dark grayish black is seen outside the white marginal line. Cilia greyish-brown, paler towards the tornus
and almost whitish towards the dorsum. UnH: All the bands are broken and discontinuous. The basal band middle segment in cell is
shifted basally in relation to the segments in spaces 1c and 7. A ‘Y‘ shaped intersection is seen between continuous
segments of bands in space 1c and 2, with the distal cell segment of the discal and the post discal band
segments in spaces 4 and 5. In addition
the other segments of the band are seen just distal to mid space in spaces 1b 6
and 7. The heart-shaped sub-marginal
series spots of dark grey are seen from space 3-6, that in space 7 is
distorted. Marginal series of flattened
crescentic dark grey spots from 3-6, followed by the white sub-marginal line
and the marginal grey-black line. Cilia
paler than that of forewing, greyish, and darker towards the tornus. Large tornal spot in space 2 occupying the
position of the heart spots on other spaces, black at the center, distally
laced with iridescent pale blue metallic scales, this is margined in pale orange
all around and the orange margin is thin distally. Two smaller tornal markings of black orange
and the metallic pale blue scales in spaces 1a and 1b, less than one-fourth
size of the tornal spot in 2. Tail
extending from vein between spaces 1c and 2, black and tipped with white (Tail
on the left side of the Type male was lost in preservation). Bases of hindwings
may have pale yellow and greenish-black scales below the basal band (Image 1B)
Male genitalia (Fig. 2E&G): From among the known species of Nacaduba from the Western Ghats, the general
structure of the male genitalia of N. sinhala
resembles N. berenice to some
extent. The similarity is in the general
morphology of valva, but the structure of vinculum,
size and stricture of uncus and the anterior end of tegumen
is quite different (Fig. 2E&G). The
armature is very different from N. kurava,
N. beroe and N. calauria. The
nearest match is to that of N. sinhala from
Sri Lanka, though there are some consistent differences. The shape and structure of annulus, vinculum
and tegumen were similar to the nominate
subspecies. The uncus was also similar
in structure, but its size and that of the sub-uncal
process was very variable amongst individuals of the same subspecies. The valva had significant structural differences from the
nominate subspecies. On lateral view,
with the whole armature in-situ, the harpe was
smoother and shorter with the rounded distal coronal margin in ramaswamii, while it was more slender with
irregular inferior margins and down-sloped coronal margin in sinhala. The
first concavity on the inferior margin was place more proximally nearer to the
angle of sacculus in ramaswamii
while it was placed more distally in sinhala
(Fig. 2F&H). On ventral view,
the structure was similar in both subspecies, but the shape of valva was very different.
The proximal part of the valva was thicker and
medial border more angulated in ramaswamii,
while it was thinner and margins sloping in sinhala. The harpe was
thicker and less curved in ramaswamii, while
it was slender and tip curved much more inward in sinhala
(Fig. 2F). On detaching the
claspers, the shape was almost as seen in the in situ view, but the distal end
angle appeared more downcurved in sinhala,
while it was slightly upcurved in ramaswamii,
this was more evident on the ventral view (Fig. 2G&H). The aedeagus was more stockier and shorter in
ramaswamii, while it was slender in sinhala (Fig. 2E&F). The coecum was larger and much globular in
ramaswamii.
The shaft was constricted a little distal to the middle of the shaft in sinhala, while no such constriction was seen
in ramaswamii.
The inferior border was more angulated in sinhala,
in contrast it was smooth in ramaswamii. The supra-zonal sheath was sharper, more
angulated and its tip angulated upwards in ramaswamii,
while it was more smooth with a straighter tip in sinhala.
Female:
Forewing length 13–14 mm (n= 2). The
female is similar to the male on the underside.
The termen and apices are more curved in
comparison (Image 1C&D).
Upperside: General color
is dark greyish-brown. UpF: Wing margins are broadly marked in dark grayish-brown,
this band being thicker at the apex, followed by the termen,
the leading edge and the distal half of the dorsum. The discal area
with white patch, occupying the lower half of the cell, half of space 2, 3 from
the origin and basal two-third of space 1b and basal half of space 1a. The basal half of the discal
patch with pale blue iridescent scales and laterally the patch is pearly white.
UpH: a pale discal patch of
white that extends from the base to the sub-marginal zone, where the
heart-shaped spots on underside are reflected as a series of spots. Space 1a is
pale greyish. Reflections of the heart
shaped sub-marginal dark spots, the marginal dark crescents, marginal lines are
as in the males. Of the largest spot is
the reflection of the tornal spot. Cell
and proximal part of space 1 is clothed in long greyish blue hairs (Image 1D).
Underside: UnF and UnH as in male, except that the bands are a bit broader and
so are the sub-marginal heart-shaped spots and the sub-marginal lines are more
arched (Image 1C).
Variation
Male paratypes show little variation in patterns on
upper and underside. The only difference
in pattern was in the size of the heart shaped spots on hindwing spaces 4 and 5
which may be occasionally larger and meet the post-discal
band, giving a crowded look. Size
variation was considerable with forewing length varying from 13–15 mm. The females had significant individual
variation, in addition to the size of the heart shaped spots on hindwing spaces
4 and 5, the extend of white coloration in uppersides
of forewing disc and the hindwing was very variable. In a few individuals there were three well
defined white spots in spaces 1b, 2 and 3.
Size variation was observed with forewing length varying from 12 to 14
mm.
Diagnosis
Male upperside violet-blue, below ground colour
is greyish to ashy, markings underside larger, ribbon scales present. The
underside forewing markings well showing on uppersides
in males. Male genitalia unlike any
other species in peninsular India. Female upperside
with shiny blue restricted to the basal half of both wings, upperside
forewing with rest of the pale patch white.
Keys to Nacaduba of Berenice
group from other regions of south-eastern Asia may not hold for taxa from
Western Ghats, because of clinal variations and subspecies differences. We observed that the disposition of bands on
underside are very variable, even on wings of a single specimen, and are not
useful characters in diagnosing species.
But the prominence of white streaks in them and the thickness of bands
may be useful in identification. Males
have straighter termens compared to females and this
feature is more appreciable in open wing images. The transparency of wings and the underside
marking showing through them is a useful character, but it must be used with
caution, because in almost all species including the Opaque Six Line Blue N.
beroe, the wings are transparent to a certain
extend. This this is useful only in
comparison of specimens in hand. The
presence of ribbon scales are a useful character in males. But these must not be confused with normal
long hairs in the cell and space 1b on upperside and
the normal battledore shaped androconial scales. Androconial scales
are structurally elongated, blunt ended short hair like scales distributed on
the upperside of the male wings. Colors will sometimes loose brilliance, hairs
may be lost in preservation and the colour of upperside may change with angles of incident light. The final word in determination of species
must be based on male genitalia, which is distinct in each species.
Generally, in Berenice group (6-line Nacaduba) prominent white lines on the broad bands
are characters that are exclusive to N. kurava
and N. sinhala,
while all other species have narrower bands with dirty or brownish stripes instead
of pure white. The male N. sinhala is easily distinguished from all other Nacaduba in Western Ghats. Ground colour
on underside is pale greyish compared to brownish of N. beroe, N. calauria, and N.
berenice and much darker of N. kurava. The species has the palest blue on
the upperside of males compared to all other Nacaduba. The
rounded forewing termen of this species distinguishes
it from species with straight termen, namely males of
N. kurava and N. beroe. The
presence of ribbon scales in males giving the frosted look on the upperside helps to differentiate the species, from males of
N. kurava and N. calauria, that lack them. The species that have ribbon scales are N.
beroe
and N. berenice. From N. berenice, it can be differentiated by much large and
prominent bands (narrow in N. berenice),
sub-marginal series of large heart-shaped dark grey spots (about the size of
the tornal spot), with apices elongated towards the base of the wing, much
darker than the grey inner stripes of the bands, more prominent on hindwings.
From N. beroe, it can be distinguished
by the rounded termen and the heart-shaped
sub-marginal series. Females of N. kurava has heart-shaped sub-marginal series, but these
are flattened and not elongated, and are always smaller than the tornal spot
and not prominent on the hindwing and upperside of N.
kurava has white discal
patches. The male N. sinhala can be confused with females of other
species too by the underside because of the rounded termen,
but may be distinguished by the white discal patches
of the other Nacaduba females. The distinct male genitalia in N. sinhala, compared to all other species is the final
method of species confirmation in case of any ambiguity. Four-line Nacaduba
of Pavana group are easily told apart by
the lack of the basal band. But
aberrations in N. hermus are
known with extra band in basal region, in which case male genital differences
have to be resorted to.
The female N. sinhala, cannot
be confused with males, but they may be confused with other female Nacaduba. All
are variable on the upperside with respect to the
extent of blue and white. N. kurava and N. sinhala
females have forewing distal end of the discal patch
pure white. The blue of this patch is
very pale sky-blue and is restricted towards the wing bases. In all other
species the discal patch is darker blue completely
with or without a purplish hue.
Sometimes in N. sinhala females
the discal patch may end in three post-discal small white spots in spaces 1b, 2 and 3, clearly
disjunct from the disco-basal patch. It
is easily differentiated from N. kurava
females by much the smaller size and the low elevational distribution <300m. Regarding elevational distribution, N.
kurava is distributed above 700m in the
subtropical and temperate forests; N. beroe
is distributed from 200–700 m in mid-elevation forests, and all other
species are seen commonly below 300m in evergreen and semi-evergreen jungles.
Etymology
The species is
named after Lord Rama, signifying the connections across the sea to Sri Lanka.
Life History
Egg: The egg is a flat disc or turban shaped with the
central region around the micropyle depressed a little. The superior surface is reticulated in a
lotus petal pattern making quadrangular cells, the intersections of these lines
bearing a centrally hollow tubercle. The
color is dirty white. The egg is laid on
the undersurface of the young leaves, axils and buds of the host plant Dimocarpus longan Lour. (Sapindaceae). Oviposition was observed usually in the
afternoons where the females were seen
in a fluttering weak flight searching for the best sites to lay eggs. Occasionally more than one egg was laid on
same leaf but by different individuals (Image 2A). Size 0.75–1 mm
Larvae: The eggs hatched in about 2–3
days. The color of the egg larva was
pale honey yellow (Image 2B). Head
capsule is of the same color as the body, mouthparts brown and eyes are black. The bod bears moderately long pale yellowish
semitransparent hairs, of these those on the dorsum and near the legs are
longer. The tiny larva was seen keeping
to the underside and scraping the lilac cuticle of that side, giving the larva
its pinkish tinge when eaten. It is of
the same color as the young leaf and very tiny to be seen, unless some sort of
magnification was used. The young larva
eats a part of the egg shell around the micropyle leaving behind the major part
of the egg shell intact. The larva moves
very slowly keeping to the undersurface of the leaf. The presence of these hatched out shell
points out the presence of the egg larva.
Size 2 mm. First instar: (Image
2C). The larva is pale waxy serous
yellow in colour.
The eye spots are black. The
structure is like that of the egg-larva.
Hairs are much shorter. The small
caterpillar keeps to the underside of the freshest leaves, eating the substance
in an irregular moth-eaten pattern. Size
2–3 mm. Second Instar: (Image
2D). The shape becomes more
flattened. Colour
is pale yellowish-white with a waxy appearance.
Like in the previous instars it keeps to the concavities of the
underside of the young leaves, eating in a moth-eaten pattern. Hairs are present, obvious and much
shorter. Size 3–4 mm. Third Instar: (Image 2E). Similar to the second instar but a bit larger and coloured pale greenish white. The habits are as the
previous instars. At this stage ants
begin to attend to the larvae. Size:
0.5–0.75 cm. Fourth Instar: (Image 2F).
The shape is almost onisciform and triangular
in cross section. Colour
is pale serous white with pink as follows- a dorsal thin line extending from
segment 3 to 12, latero-basal thicker lines just above the flange covering the
legs all along the side from the segment
2–12, whole of the segment 2 and 3. Of
these three lines the dorsal line is the darkest. The central triangular plate on segment 2 is
milky white so are the lateral organs on segment 12. The whole body is covered in very small,
transparent star shaped tubercles giving a rough appearance on
magnification. Hairs are seen on the
lateral flanges, front and rear ends.
Those on the lateral flanges are the shortest and curved and that on the
front end and anal plate are longer, the latter being the longest. Size: 0.75–1
cm, habits are like the previous instars, but this a much bolder in feeding
facilitated by the ants that attend it.
Feeding is more active and the whole leaf margin is consumed instead of
the cuticle and it prefers a little more mature leaflet. Final Instar: (Image 2G&H). The shape is onisciform. Segment 2 and anal plate is
semi-circular. Mid dorsal plate in
segment 2 is flower shaped and milky white. Each segment is flanged out and
tumid giving a blunted serrated look.
The highest point is at about the middle of the body. Colour is pale sap
green with a waxy yellow shade especially along the baso-lateral
flanges. Sometimes pink forms are also
seen. Head is completely hidden under
segment 2 and is pale greenish-yellow, eyes black and mouthparts pale
brown. Body has sparse hairs along the baso-lateral flanges, on the edge of segment 2 and anal
plate. Whole body is clothed in tiny
tubercles giving a rougher texture on magnification. Spiracles circular and white. Segment 11 has the transverse gland opening
at its hinder margin. Segment 12 bears
the lateral organs, just postero-lateral ton the
spiracles, and the tip of the thin extruded gland is pale pinkish-brown. Length 10–15 mm. Breadth 5–6 mm. The total duration of larval stage is 18–20
days.
Pupa: (Image 3B–D). Shape of the pupa is as in all Nacaduba, a short spindle with wide abdomen. On dorsal view, front is almost squarish with
sides rounded off. The anal end is
rounded. The broadest part on the pupa
is around the level of the distal end of the wing cases. On lateral view, the head has a dorsal
convexity, the angle between head and thorax is obtuse, thorax is humped, the
constriction between thorax and abdomen is very shallow and a smooth
concavity. The highest point is at the
mid-level of the wing cases. The abdomen
has a uniform convexity. Pupa is secured
with the mid-body band and the cremaster.
The whole surface is finely reticulo-rugose
and bears large black spots and tiny brown spots that coalesce to form
blotches. The general colour is waxy pale yellowish-brown with a hue of rose on
the head, thorax and wings; and opaque yellowish-pink with a brown wash on the
abdomen. Wing cases are pale waxy
brown. The whole body is marked in dark
brown and black as follows- there is a dorsal band running from head to tail,
this band has a large black spot near the joint of the head and thorax, there
are two black spots as large as the anterior one, just above where the wings
begin, another pair of black spots are present in the lateral ends of the first
thoracic segment. A pair of spots in all
segments on the dorsolateral aspect except in second thoracic segment. The dorsal band may form a large spot the
rear end. Rest of the body bears tiny
blackish-brown spots that may join with the adjacent ones. Pupation takes place under the leaf or on the
stem of the plant (Image 3A). The
butterfly eclosed in 7–10 days.
Ecological notes
The species appears to breed more during the
north-east monsoons, though the breeding season extends from September to
January, with peak in October. In Sri
Lanka the larvae are attended by Technomyrmex
(van der Poorten &
van der Poorten 2013), while it is occasionally attended by Technomyrmex albipes (Smith,
1861) and Nylanderia species in southern India
from stages 3-final instar (Image 3E&F).
Distributional range
This is the first record of the species N. sinhala outside its endemic range in Sri Lanka. Thus, the endemicity of the taxon is now
limited to the Western Ghats complex (Western Ghats and Sri Lanka), more
specifically Agasthyamalais and Sri Lanka. The altitudinal range is below 300m (Fig. 1).
Discussion
This paper adds one more taxa to the butterfly list of
Western Ghats and hence to that of butterflies of mainland India. The Sri
Lankan taxon was originally described as ‘Nacaduba
berenice ceylonica Fruhstorfer’. Later,
Ormiston (1924) renamed this, accepting the
morphological differences as Nacaduba sinhala; and the Sri Lankan taxon representing Nacaduba berenice was
named Nacaduba berenice ormistoni by Toxopeus
(1927). N. sinhala
was believed to be restricted to Sri Lanka as per Ormiston (1924), Evans (1932),
Woodhouse (1947), and van der Poorten &
van der Poorten (2018). The early stages and the larval hostplants of
Nacaduba sinhala
were documented by van der Poorten &
van der Poorten (2013), as Dimocarpus longan
Lour. (Sapindaceae).
The species is said to be distributed from 100–900 m. The butterfly
flies year round and is migratory, the peak flight season appears to be just
before the start of the south-west monsoons according to van der Poorten & van der Poorten (2018). In contrast, the southern Indian subspecies
seems to be non-migratory as far as known and present in low numbers all around
the year. The peak flight season being
during the North-East monsoons from September to November. The larva of the species is monophagus and feeds on Dimocarpus
longan Lour. (Sapindaceae)
both in Sri Lanka and South India. We
found that the southern Indian taxon is morphologically similar to the nominate
species from Sri Lanka but differs in its male genitalia structure. The differences and the geographical
locations, suggest they have diverged possibly to a subspecies level. Further
phylogenetic works might be needed to elucidate the molecular divergence and
with sufficient variation it may be subsequently raised to species status.
Revised Key to Nacaduba
line blues of Western Ghats of peninsular India
A.
Underside forewing no basal pair of pale lines 4-line blues (Pavana group)
Underside
forewing inner sub-marginal band on forewing continuous, broad and diffuse and
continuous in both sexes (Image 5A) .........................................................................................................................
Nacaduba pactolus
continentalis Fruhstorfer,
1916
Underside
forewing inner marginal band of forewings made of separate narrow lunules in
both sexes (Image 5B) .....................................................................................................................................
N. hermus sidoma
Fruhstorfer, 1916
B.
Underside forewing with basal pair of pale lines: 6-line blues (Berenice
group)
Termen of
forewing straight in middle in spaces 2–6 in males, forewing apex produced,
especially evident in open wing
Males pale violet blue, below markings regular and
prominent ground color greyish, clearly showing
through above, upperside hindwing disc in males not
clothed in hair-like scales thus lacking the frosted look, females upperside forewing and upperside
hindwing discal patch broad, pale bluish-white and
lacks the white post discal spots (Image 5C). Male genitalia distinct (Fig. 2A) .......................................................................................................................................
N. kurava canaraica
Toxopeus, 1927
Males
upperside dark violet blue, below markings narrower,
duller not clearly showing through above, ground color
brownish, wings rounded than N. kurava;
UPH disc in males clothed in hair like ribbon scales giving frosted look, females UFW discal
patch restricted, bluish and traces of pale post discal
spots, female UPH brown with bases purple blue (Image 5D). Male genitalia distinct (Fig.2C) ……........................................................................................................…………..N.
beroe gythion
Fruhstorfer, 1916
Termen of
forewing convex, forewing apex rounded in both sexes
Ground
color on underside browner, stripes narrow off-white;
males upperside dark steely shining blue, ground color brownish, no ribbon scales hence lacking frosted
look; markings on underside well-defined and narrow. Females upperside
forewing discal patch restricted with bluish scales
and traces of pale post discal spots, female UP
purple (Image 5F). Male genitalia
distinct (Fig. 2B) ...................................................................................................................................................
N. calauria evansi
Toxopeus, 1927
Males
upperside violet blue, below ground color greyish to ashy, markings on underside larger, ribbon
scales present
Ground
color browner in dry season and greyish in wet season
form, stripes narrow off-white (Image 5E); underside forewing markings not well
showing on upperside forewing. There may be heart-shaped spots on the
sub-marginal areas of both wings in the west season form, but the spots
are never elongated or thicker as in N. sinhala,
especially in the forewings; females UPF and upperside
hindwing broad discal bluish patch with no discal bluish spots, female upperside
shining blue beyond the half of the wings, ribbon scales present on male
forewing giving a frosted look. Male
genitalia distinct (Fig. 2D).….N. berenice
plumbeomicans (Wood-Mason & de
Niceville, 1881)
Ground
color pale greyish, stripes broad and white giving a
crowded appearance especially on the post-discal
region of hindwing. UNF markings well
showing on UPF in males, female UP with shiny blue restricted to the basal half
of both wings, UPF with rest of the pale patch white. Both sexes both wings with a sub-marginal
series of large heart-shaped dark grey spots (about the size of the tornal
spot), with apices elongated towards the base of both the wings, much darker
than the grey inner stripes of the bands, more prominent on hindwings where
they almost touch the post-discal bands (Image
4). Male genitalia distinct (Fig.
2E&G)
.........................................................................................................................................................
N. sinhala ramaswamii
ssp. nov.
For
figures & images - - click here
References
Corbet, A.S. (1938). A revision of the Malayan species of the Nacaduba group of genera (Lepidoptera: Lycaenidae). Transactions of the Royal Entomological
Society of London 87: 125–146. https://doi.org/10.1111/j.1365-2311.1938.tb00731.x
Corbet, A.S. & H.M. Pendlebury
(1992). The Butterflies of the Malay
Peninsula. 4th edition. Revised by J.N. Eliot. Malayan Nature
Society, Kuala Lumpur, 595pp.+69pl.
Evans, W.H. (1932). Identifications of Indian Butterflies, 2nd
edition. Bombay Natural History Society, Bombay. x+454pp.+32pl.
Larsen T.B. (1987). The butterflies of the Nilgiri
mountains of southern India (Lepidoptera: Rhopalocera).
Journal of the Bombay Natural History Society 84(2): 291–316.
Ormiston, W. (1924). The Butterflies of Sri Lanka, H.W. Cave
& Co., Colombo, 143pp.
Toxopeus, L.J. (1927). Lycaenidae Australasiae III. Treubia 9(4): 423–435.
van der Poorten,
G.M. & N.E. van der Poorten (2013). New and revised descriptions of the immature
stages of some butterflies in Sri Lanka and their larval food plants
(Lepidoptera: Lycaenidae). Part 1: Polyommatinae and Theclinae, in
part. The Journal of Research on the Lepidoptera 46: 25–49.
van der Poorten,
G.M & N.E. van der Poorten (2018). Field guide to the Butterflies of Sri Lanka. Lepodon Books, Toronto, 250pp.
van Hook, T., E. Williams, L.
Brower, S. Borkin & J. Hein (2012). A standardized protocol for ruler-based measurement
of wing length in monarch butterflies, Danaus plexippus
L. (Nymphalidae, Danainae).
International Journal of Tropical Insect Science 22: 42–52.
Woodhouse, L.G.O. (1947). Observations on species of Nacaduba moore, and some other Lycaenidae
from Ceylon. Proceedings of the Royal Entomological Society of London.
Series B, Taxonomy 16: 3–9. https://doi.org/10.1111/j.1365-3113.1947.tb00838.x