On the occurrence of Common Baron (Lepidoptera: Nymphalidae: Limenitidinae: Euthalia aconthea Cramer, 1777) in the Delhi area and analysis of abiotic factors affecting its distribution in India

This paper gives details of the occurrence of Euthalia aconthea from Delhi area situated in the Indo-Gangetic plains. Occurrence records of this species suggest that it is most frequent in five zones of India, despite the fact that its main larval food plant Mango Mangifera indica is abundantly available almost throughout India. Possible abiotic factors are hypothesized for this distribution.


INTRODUCTION
The distribution range of Euthalia aconthea covers India, Pakistan, Sri Lanka, Nepal, Bhutan, Bangladesh and Myanmar (Kehimkar 2008). Its range is alternatively described as all of south and south-east Asia, from Sri Lanka to the Sunda Island (Kunte 2000). This distribution however is not uniform and this butterfly appears to be practically absent from some parts of the Indo-Gangetic plains despite abundance of its larval food plant. Till date this butterfly has not been reported from Delhi area.
The most common and preferred larval host plant of this butterfly is Mango Mangifera indica. In coastal Maharashtra and perhaps in other states too, it also feeds on Cashew Anacardium occidentale (Kunte 2000). Mango and cashew both belong to the family Anacardiaceae. Mango occurs wild or semi-wild nearly throughout India, in tropical and sub-tropical hilly forests particularly near nullahs and ravines. It is common in the sub-tropical Himalaya, hills of Western and Eastern Ghats and the forests of central India, Bihar, Odisha, Assam and the Andaman Islands. It is grown in plantations and orchards, but more often in homegardens, field borders and roadside avenues (CSIR 1959).
There are three main papers on the butterflies of Delhi: Donahue (1966), Ashton (1973) and Larsen (2002). On the basis of the then available records from Lucknow, Lahore and Amritsar, Donahue kept this butterfly in the "hypothetical list" of butterflies for Delhi area at the end of the paper as Euthalia garuda (Moore, 1857); a synonym for Euthalia aconthea Cramer, 1777. Subsequent papers (Ashton 1973;Larsen 2002) did not mention this species as it was never recorded from Delhi area. In the first part of this paper (Part-A), I present the records of Euthalia aconthea from the Delhi area for the period 2003-2013. The second part of this paper (Part-B) examines the main abiotic factors (rainfall, temperature, insolation, soil moisture and topography) to understand the reasons as to why this butterfly is not common in Delhi despite an abundance of mango. The origin and native range of mango has also been analyzed to get an insight into the current distribution pattern of Euthalia aconthea.

PART-A Euthalia aconthea -Delhi area records
I first spotted this butterfly on 10 September 2003 at 09:00hr in Sector 33, Noida and made a rough sketch of the butterfly in my pocket diary. As Euthalia aconthea was not supposed to be a Delhi butterfly and Peter Smetacek's booklet "Butterflies of Delhi" (which is based on Donahue 1966) did not include this butterfly, it took me some time to positively identify this butterfly. On 12 September 2003 one female landed in our front courtyard and was brought inside. I made a coloured pencil sketch of this brown butterfly with white spots in my diary and re-deposited the butterfly from where it was picked. This gave me an opportunity to closely examine the butterfly and positively identify it to be a Euthalia aconthea.
On 23 Sept 2003 I photographed one mud puddling at 13:30hr in Sector 33, Noida. On 21 Oct 2003 one male was spotted on the road at 09:30hr (Images 1 & 2). It was searching for the liquid nutrients on the edges of a fresh cow dung using its long green proboscis. At 13:30hr I found this butterfly dead on the same spot crushed by some vehicle. These are the records of the initial sightings of Euthalia aconthea from the Delhi area.

Study Area
Sector 33 and 24 of Noida (28.60N, 77.35E), a satellite town of Delhi. Sector 33 is a residential area with small home gardens and potted plants in almost all the houses. Sector 24 is an institutional area with numerous offices and educational institutes. A busy main road separates the two sectors. Karanj (Pongania pinnata), Gulmohar (Delonix regia), Kasod (Cassia siamea) and Ashoka (Polyalthia longifolia) are the main trees planted on both sides of the sector roads. In addition, Peepal, Jamun, Mango, Mulberry, Currypatta (Murraya koenigii), Lemon and Guava are also quite common in the area.

METHODS
After recording its initial presence in Noida in 2003, I kept a record of its sightings around my home in Sector 33, Noida for the period 2003-2013. Two trees are of special interest to these observations: first a Mango tree just across the road and the other a Guava tree that we have planted in front of our house. Both the trees are visible from our dining area and kitchen windows. Mango is the larval food plant. Rotting guava on the Guava tree (half-eaten by the fruit bats in the night) are a favourite with the adult butterflies. Both the trees remained under continuous observation by us for any bird, bat or butterfly activity. Every day between 09:00-09:30 hr, I came out of my house and scanned these trees for the presence of any butterfly. Again, while taking lunch between 13:15-13:45 hr I kept a continuous watch on the birds and butterflies visiting these trees. At 13:45hr I once again came out and scanned the area for butterflies.

RESULTS
Sight records for the period 2003-2013 are plotted in Fig. 1. It is evident from Fig. 1 that though not present every year, Euthalia aconthea is generally spotted in March and October in very low numbers. With this report presence of Euthalia aconthea from the Delhi area is confirmed and this butterfly may be added to the list of Delhi butterflies. Uttar Pradesh is the largest mango producing state of India. The main production centres are located in two clusters: first around the Lucknow -Faizabad axis, and the second around a line joining Saharanpur, Muzzafarnagar, Meerut and Bulandshahar. Delhi lies in the immediate vicinity to the west of this second cluster and therefore these records of Euthalia aconthea from Delhi may be the western most limit of the range of this butterfly at this latitude. Beyond Delhi, to the west, lies the desert of Rajasthan where this butterfly does not exist. Interestingly, even at the centre of the most prolific mango belt around Lucknow, this butterfly is not very common (de Rhe-Philipe 1902) and therefore on the fringes it is bound to exist at extremely low levels, making regular sightings in Delhi a matter of chance.

PART-B Euthalia aconthea -Distribution pattern in India
As per Evans there are five subspecies of this butterfly in India: subspecies meridionalis is distributed from southern India to northern Kanara, subspecies anagama is distributed from Bombay to Odisha and also Kangra to Kumaon, subspecies suddhodana in Bengal and Sikkim, subspecies garuda in Assam-Burma and a rare subspecies acontius is restricted to the Andamans (Evans 1927).  In order to fully understand the distribution pattern of Euthalia aconthea in India past sighting records have been collected and compiled. In the present study subspecies level classification has not been used and all the sightings and published records have been considered at species level. These records are mostly for India but some records of Pakistan, Bangladesh, Bhutan and Myanmar have also been included using data from the Journal of Bombay Natural History Society, Journal of Threatened Taxa, Zoos' Print Journal other butterfly books and a few additional papers mentioned in the reference section. Compiled records are placed in Appendix 1. Based on the latitude and longitude of the places these records have been transferred to Google Earth to get a visual feel of the distribution pattern. Fig.  2a shows the locations from where its presence has been reported. Fig. 2b shows the locations where it is reported to be not present. Fig. 2a reveals that Euthalia aconthea appears to be present most frequently in five zones in India roughly corresponding to northeastern hill regions of Sikkim-Assam-Tripura-Dhaka, central Indian hills of Madhya Pradesh and Chhattisgarh, Western Ghats, sub-tropical Himalayan forests of Himachal Pradesh-Uttarakhand, and Andaman Islands. Abundance levels at these locations have been judged by the descriptions given in the source and the same are briefly mentioned in Appendix 1. Butterfly records are however very incomplete in India and many areas have not been surveyed or surveyed very poorly, therefore these five zones remain speculative.

Presence of Euthalia aconthea in the five zones
Zone 1: The northeastern hill regions. In Sikkim it is common in the lower hot valleys of Rangpo, Rangeet and in Singtam. Also seen in cities and crowded markets, on rotten vegetables and fruits (Haribal 1992). In Bhutan it is a common butterfly (Wangdi 2012). It is present in Arunachal Pradesh (Gogoi 2012), Assam (Gogoi 2013) and Tripura (Majumder 2013). In Upper Neora Valley National Park, West Bengal, it is present throughout the year (Singh 2012). In Dhaka, Bangladesh, it is not rare (Larsen 2004).
Zone 2: The hills of central India. One record describes this butterfly to be common and easily attracted to Mohwa refuse in the Central Provinces (Betham 1890). However a recent four year long fieldwork carried out in the five national parks of central India (Panna, Bandhavgarh, Kanha, Pench and Satpura) in the 1990s reveals Euthalia aconthea is "Not Rare" in central India (Shrivastava 2008). This means that even in the heart of the hilly jungles of central India receiving annual rainfall of 1,300-1,500 mm, this butterfly is no more abundant or common. As more and more hills are demolished in Madhya Pradesh, Chhattisgarh, Jharkhand and Odisha by massive mining operations for extracting limestone, coal, iron, bauxite and other minerals from this mineral rich area of India, it is likely to become even more scarce. Zone 3: The Western Ghats. Euthalia aconthea is common throughout the year in Dangs forests (Shull 1963), plentiful in Goa (Larsen 1987), occurs throughout the year in Bondla Wildlife Sanctuary, Goa (Borkar 2004). It is found all over Coorg (Yates 1931). It occurs throughout the year in Bangalore and becomes abundant in September (Yates 1933). It is sometimes very common in places like Bangalore (Larsen 1987). The book "Some South Indian Butterflies" (Gunathilagaraj 1998) informs that as mango, its principal host plant is cultivated everywhere, it is now very common even in cities and crowded markets, on rotten vegetables and fruits, toddy, plant sap and damp patches. Though exact location for this description is not mentioned in the book, this appears to be a description for areas around Bangalore. However it is rare in the Nilgiris (Larsen 1987).
Zone 4: The Sub-Himalayan Tract. Euthalia aconthea is common in Bir-Billing area of Dhauladhar range in the Joginder Nagar Valley of Kangra, Himachal Pradesh, in northwestern Himalaya. Arora (2009) reports its presence in Kangra and Shimla districts of Himachal Pradesh. It was once very common in Dehradun (Mackinnon 1898) and is still reported to be common (Singh 2016). It is also reported from Mussoorie (Ollenbach 1931).
Zone 5: The Andaman Islands. Subspecies acontius is a rare species confined to the Andaman Islands.

Factors Affecting Distribution
As the distribution range as marked in Fig. 2a, is much smaller as compared to the distribution range of its main larval food plant mango, climatic factors are perhaps the range limiting constraints for this butterfly. Rainfall, temperature, insolation (incoming solar radiation), soil moisture and topography of these zones have been examined as these are believed to be the main abiotic factors influencing the survival, growth and range limits of insects. Rainfall and temperatures have been taken Soil Moisure Index is expressed in % using following formula (Thornthwaite): Soil Moisture Index = {(P -PET) / PET} x 100 Where P = Total annual Precipitation in mm PET = Potential Evapotranspiration Table 1 summarizes the temperature and rainfall data pertaining to these five zones and Table 2 shows data related to topogrphy, insolation and soil moisture. Fig. 3 showing Normal Distribution of Monsoon Rainfall in India reveals that five zones (Fig. 2a) where Euthalia aconthea appears to be most frequent correspond to the areas of high rainfall receiving more than 1,250mm of rainfall during the monsoon season. Figs. 4 and 5 show that these are also areas of moderate insolation and positive soil moisture index.

Preferred Habitat
After examining Table 1 and Table 2 and also relative abundance levels (Appendix 1), climatic conditions of the preferred habitat of Euthalia aconthea may be defined as below: 1. Total Annual Rainfall: More than 1,600mm. 2. Average Annual Temperature: < 28.5 0 C, Average Annual Temp Range of 10 0 C. 3. Insolation: 4.6-5.6 kWh/(m 2 .day) 4. Soil Moisture Index: 20-100 or more (i.e., Humid or Perhumid). 5. Topography: Hilly terrain with valleys and gorges. On the basis of these five parameters, Lucknow offers a better habitat as compared to Delhi. Lucknow

Larval food plants
This part examines the original native range of wild mango and the extended range of cultivated varieties of mango to show that five zones of very high rainfall where Euthalia aconthea appears to be most abundant are also the centres of origin and evolution of wild mango.

Origin of Mango
Although its precise centre of origin is not known, mango is probably indigenous to the lower montane forests of eastern India, Bhutan, Bangladesh and Myanmar between latitudes 16 0 N and 28 0 N. (Parrotta 1993). Truly wild mango trees have been recorded in Bangladesh (Chittagong Hills), northeastern India (Assam valley) and Myanmar (ICAR 2014). The evergreen mango tree is indigenous to Asssam, Western Ghats, Satpuras and parts of the sub-Himalayan tract (Sagreiya 1994).

Climate for Mango
The native range of mango is characterized by an annual rainfall of between 1,500-2,600 mm, with a dry season of 4-5 months between November and March. In its native range, mean annual temperatures range from 24-27 0 C, with mean minimum temperatures of 11-17 0 C and mean maximum temperatures of 32-34 0 C during the coldest and warmest months, respectively (Parrotta 1993).

Hills of central India
"The Central Provinces is generally a mountainous country, with plateaux, plains, hills and valleys. At the entrance of the glen are magnificent old mango trees, their roots entwined amongst the rocks, their boughs o'ershadowing the stream" (Betham 1890). The Sal forest dominated by Shorea robusta cover the top of the hills. The mixed evergreen forest are in the middle zones of the hills and around the Pachmarhi plateau dominated by Mangifera indica, Terminalia tomentosa, Terminalia bellerica, Sygygium cumini and Anogeissus latifolia. It is one of the areas where natural forests support large sized wild mango trees. Along streams and water courses fine riparian forests are encountered with rich mango, Jamun, Arjun and Manilkara tree. Topographical changes and hill directions have different micro-climatic conditions. The hill not facing the sun has always more moisture and humidity compared to the side facing the sun and on these faces there is a dominance of mixed evergreen forest, dominated by Sal and mango (Singh 2001).

The Western Ghats
In wet evergreen forests of Western Ghats mango occupies a codominant position in association with jamun and jack fruit tree (Hawkins 1986). In 1837 Col. Sykes noticed a huge mango tree, at Bhimashankar on the crest of the Sahyadris, which was stated to be 80ft (24m) high (Dixon 1895). In the recent exploration mission carried out by the Indian Institute of Horticultural Research (IIHR), Bangalore, 34 unique types of wild mango were collected from the Western Ghats which is the hotspot for the pickle mangoes. These indigenous types are specific to the humid, tropical rainforests and are carried away by the rainwater and propagated through the seeds, resulting in rich diversity (Vasugi 2012).

Sub-Himalayan tract
In the outer hills of the western Himalaya (Himachal Pradesh and Uttarakhand) there is a narrow belt of high rainfall area that supports wild Mangifera indica. Records of the Botanical Survey of India for the area mention that "Mangifera indica, Linn, is not seen in Chamba, but there are many fine trees in the Kangra Valley" (Gammie 1898). A giant mango tree; over 100 year old is reported from Chandigarh with a trunk girth of 9.6m and crown area of 2,250m 2 (CSIR 1959). Chandigarh is located in the foothills of Shivalik, the outer most Himalayan range, about 90km from Joginder Nagar.
In Uttarakhand, as per Flora of British India (Hooker 1879), Mangifera indica occurs in tropical Himalaya; alt 1-3,000 ft (1-914 m) from Kumaon to Bhotan Hills. In Forest Flora for Kumaon, Osmaston writes: Mangifera indica occurs wild and is apparently indigenous, in shady moist ravines in the outer hills up to 3,000ft (914m). It is also abundantly planted throughout the area up to 914m (Osmaston 1927). These descriptions appear valid for Dehradun valley also which lies in the neighbouring Garhwal Himalaya as mango is reported to be "cultivated and almost wild in Saharanpur and Dun" (Kanjilal 1928). Western Himalayan region provided germplasm of the wild relatives of Mangifera indica collected under National Agricultural Technology Project (NATP) on Sustainable Management of Plant Diversity (Pandey 2005).
In Himachal Pradesh heaviest rainfall of over 2,500mm is observed in a 13km wide strip along the southern slopes of Dhauladhar for 72km right from Dharamsala to Joginder Nagar in Kangra District. A gradual decrease in rainfall is recorded in every direction from the centre of this belt. First a ring of 1,250-2,500 mm of rainfall is formed followed by 750-1,250 mm which then further gets reduced to 600-350 mm in the inner areas between Dhauladhar and Pangi range (Joshi 1984). District Chamba lies between Dhauladhar and Pangi range in the rainshadow of Dhauladhar. Dehra Dun is a gently sloping valley, 45 miles long and 15-20 miles broad between the Himalaya in the north and the Shiwalik Hills in the south. It is divided in two parts by a connecting ridge from which eastern Dun slopes down to the Ganga and the western Dun to Yamuna. On the north the outer range of the Himalaya rises abruptly to a height of 7,000-8,000 ft (2,134-2,439 m), with the hill stations of Mussoorie, Landour and Chakrata (The Imperial Gazetteer of India 1908). Dehradun and adjoining areas receive an annual rainfall of more than 2,000mm. Dehradun is capital of Uttarakhand.

The Andaman Islands
The Andaman Islands are a mass of hills running north to south and enclosing narrow valleys and the whole area is covered by dense tropical forest. The highest point is Mount Saddle Peak, 732m. The average annual rainfall is about 3,048cm (Padalia 2004). True wild mango is distributed in India, Burma, Andamans etc. (Mukherjee 1972).
So it is seen that the 5 Zones where Euthalia aconthea appears to be most abundant are also the centres of origin / evolution of the mango.

Mango range extension: Cultivated varieties of Mango in India
Mango has been cultivated in India for 4,000 years (Hawkins 1986). Owing to its cultivation and dissemination for thousands of years, in India semiwild trees can be found in the forests throughout the subcontinent. Total number of distinct mango varieties named and maintained in India has been estimated to be over one thousand. About 30 varieties are commercially grown in India (ICAR 2014). Under the Moghul emperor Akbar (1556-1605), the best selection of seedling mangoes were planted in large orchards. The 'Lakh Bagh', a mango orchard of 1,00,000 trees was planted near Darbhanga in Bihar (Mukherjee 2009). All the cultivars of mango belong to the single species mangifera indica L (Mukherjee 1972).

Cashew (new larval host plant) in India
Cashew (Anacardium occidentale), a native of Eastern Brazil was introduced to India by the Portuguese about 500 years back. It was first introduced in Goa and now it is grown in the coastal regions of Kerala, Karnataka, Goa and Maharashtra in the west and Tamil Nadu, Andhra Pradesh, Odisha and West Bengal along the eastern coast. To a limited extent it is also being cultivated in Chhattisgarh, northeastern states (Assam, Manipur, Tripura, Meghalaya and Nagaland), and the Andaman & Nicobar Islands (Salam 1999).

CONCLUSION
There are five distinct high rainfall zones in India that receive an average annual rainfall of more than 1,250mm. These zones are northeastern India, hills of central India, Western Ghats, sub-tropical Himalayan forests and Andaman Islands. These five zones are also the centres of origin and evolution of mango. Ignoring its recent association with cashew, Euthalia aconthea is largely a monophagous butterfly on mango and it appears to be most frequent to these very same distinct zones of high rainfall and wild mango. Euthalia aconthea appears to have refused to follow the expanding range of the cultivated varieties of mango to relatively drier areas, away from hills and mountains. Cashew (new introduced plant) has been accepted in the existing range but the original host plant (mango) has failed to sufficiently attract it to the new territories beyond its native range. How hills and valleys of the native range and associated climatic factors affect the growth and survival of this butterfly during different stages of its lifecycle is yet to be fully understood. Fig. 6 summarizes the distribution pattern of Euthalia aconthea in India based on the findings of this study. However as Part-B of this paper is based on the published occurrence records of Euthalia aconthea, more research on the ground is required in different zones to prove the proposed hypothesis.
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F f F fi g 6 . D fi s tt r fi b u tt fi o n p a tt tt e r n o f E u tt h a l fi a a c o n tt h e a v fi s -à -v fi s M a n g fi f e r a fi n d fi c a r a n g e fi n I n d fi a . N a tt fi v e R a n g e o f w fi l d m a n g o E x tt e n d e d R a n g e o f c u l tt fi v a tt e d m a n g o M a n g o a b s e n tt Silent Valley