Light attracted butterflies: a review from the Indian
sub-region with an inventory from West Bengal, India
Soumyajit
Chowdhury 1 &
Rahi Soren 2
1 School of
Oceanographic Studies, Jadavpur University, 32 Raja S.
C. Mullick Road, Kolkata, West Bengal 700032, India
2 Ecological
Research Unit, Department of Zoology, University of Calcutta, 35 Ballygunge
Circular Road, Kolkata, West Bengal 700019, India
Email: 1wildlifesc@gmail.com (corresponding
author), 2 rahisoren@gmail.com
Date of publication (online): 26 June 2011
Date of publication (print): 26 June 2011
ISSN 0974-7907 (online) | 0974-7893
(print)
Editor: Peter
Smetacek
Manuscript
details:
Ms # o2476
Received 03
June 2010
Final revised
received 02 May 2011
Finally
accepted 13 May 2011
Citation: Chowdhury,
S. & R. Soren (2011). Light attracted butterflies: a review from the Indian
sub-region with an inventory from West Bengal, India. Journal
of Threatened Taxa 3(6): 1868–1871.
Copyright: © Soumyajit
Chowdhury & Rahi Soren2011. Creative Commons Attribution
3.0 Unported License. JoTT allows unrestricted use of this article in
any medium for non-profit purposes, reproduction and distribution by providing
adequate credit to the authors and the source of publication.
Acknowledgements:We are grateful to the Bombay Natural History Society
for making an access to the necessary articles related to the present context
by bringing out the DVD on 100 volumes of the Journal of the Bombay Natural
History Society.
For figures, tables -- click here
Some of the nocturnal
Lepidoptera, mostly moths (Heterocera) are negatively heliotropic but
positively phototactic, being impelled by an irresistible attraction to a
bright lamp (Willey 1867). Phototaxis (attraction to artificial lights) has, however, been
explained to be somewhat different from heliotropism (attraction to
natural/sunlight) by Willey (1867). On the basis of exploiting natural light/sunlight, butterflies
(Rhopalocera) can be categorized in two broad groups, viz., (i) the diurnal
ones, with day flying habit and retiring at dusk, and (ii) the crepuscular
ones, with a flying habit at dusk and even low-light conditions. For the night, they usually take
shelter among bushes and trees. However, several observations regarding their occasional response to
artificial light have been reported from both old and new worlds.
The occasional
phenomenon regarding attraction of butterflies to artificial lights in the
Indian sub-region have been reported in the literature. The first report was published by J.I.
Alfrey in a paper by Best (1951) concerning the sighting of Lime Butterfly (Papilio demoleus demoleus Linnaeus) attracted to “Kitson
Oil Lamps” at night at the railways station in Jhansi (southern Uttar Pradesh
State, India) during a migration. Later, more detailed observations were published by Usman (1956),
Donahue (1962), Shull (1964), Shull & Nadkerny (1967), Nadkerny & Shull
(1968), Sharma & Chaturvedi (1999), Nair (2001) and Sharma & Chaturvedi(2005).
The present article
deals with a review on the earlier observations on light-attracted butterflies
in the Indian subcontinent with additions of four new species responding to the
same from West Bengal. The primary
objective is thus to elaborate the diversity and seasonal inclination of
light-attracted butterflies in the Indian sub-region along with a possible
explanation for such an unusual phenomenon.
Materials
and Methods: The primary review work regarding the
cases of light-attracted butterflies in the Indian sub-region from the period
between 1951 and 2005 was accomplished through literature surveys.
Both inadvertent
observations as well as designed experiments were undertaken during that
period. However, the records for light-attracted butterflies in the urban
(Kolkata) and forested regions (Samsing and Buxa of the Dooars) of West Bengal
are new from this region and resulted from incidental observations during the
period 2008 to 2009. No
intentional light-traps were designed in those places for attracting
butterflies at night.
Results:The light-attracted butterflies recorded
by the earlier authors from 1951–2005 revealed 27 species belonging to
five families. Table 1 shows a
list of the species, along with the place; season of
observation and the type of artificial light source to which they were
attracted. The observations by the
present authors (2008–2009) report six butterfly species that were
attracted to light at night from Kolkata and Dooars (Samsing and Buxa) regions
of southern and northern West Bengal, India. Four species reported here, viz. Papilio polytes Linnaeus, Tanaecia lepidea Butler, Neptis sp. and Pelopidas mathiasFab. are additions to the known butterflies subject to
this phenomenon in India (Table 1), while Chilades lajus Stoll. and Melanitis ledaLinn have also been reported earlier by Sharma & Chaturvedi (2005) from
Maharashtra and by Donahue (1962) from Uttar Pradesh respectively. All the species were observed as single
individuals during a single light-attraction event. No mass attractions were thus observed for the species in
West Bengal. The observations by
the present authors are detailed in Table 2.
A total of 31 species of
butterfly resulting from the past and present observations showed occasional
response to a variety of artificial lights in different parts of the Indian
region. Among these, nymphalids
(35.48%) outnumber the rest, followed by pierids (22.58%), lycaenids (19.35%),
hesperiids (12.9%) and papilionids (9.68%) (Fig. 1). The observations (Tables 1 & 2)
also reveal a seasonal inclination for such a phenomenon, as the maximum
incidents were recorded during the monsoon months (June–October) in the
Indian sub-region (Fig. 2).
Discussion
and Conclusion: Crepuscular species, like Melanitis leda,
are more active in the dark than the sun-loving, diurnal species, and thus are
attracted more frequently to artificial lights (Donahue 1962).
The phenomenon of light
attraction among butterflies has been found to be inclined more in the monsoon
season (June–October) in the Indian sub-region. Heavy downpours during the monsoon months may disrupt the night-time shelters of some butterfly individuals, inducing
them to move from their former preferred site to a new one. In the absence of optimum light, they
fail to do so using visual cues. In
that case, a source of artificial light with an intensity enough to stimulate
them to get attracted may serve the purpose of utilizing their visual potency
to search for a safe shelter. Throne (1961) also suggested that a butterfly mayfly at light if it is disturbed at night and is near the light in the first
place. Heitzman (1965) was certain
that a large percentage of the specimens collected at light were startled from
their resting places in nearby trees or bushes by the collector or some larger
insects attracted towards light. Donahue (1962), however, noted that the butterfly numbers were greatest
during the monsoon months, particularly in arid areas (like New Delhi, where
his observations were made) when there is an abundance of food. He therefore pointed out the
coincidence of the population peak with the rainy season, and either one or
both these factors might influence the activity of certain species at
light. He also indicated the
probable effect of temperature upon the nocturnal activity of the observed
species, since most of his observations were in the monsoon months, with no
record of any species in winter.
Furthermore, as in most
cases of butterfly attraction towards a light source near their resting places, occasional
incidents were reported where specimens were drawn from a considerable distance
(Heitzman 1965). Donahue (1962)
also argued that in some instances the butterfly would have to expend some
effort to reach that light. Moreover, approaching that source, many of them tend to settle near the light.
As light is an important cue that attracts insects to sources of heat
(Schowalter 2006), the warmth obtained on getting nearer the light may also
help in thermoregulation.
Further observations and
experimentations on Indian butterflies being attracted to light at night may
provide a less speculative explanation of phototactic and nocturnal
behaviour.
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