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A record of the great eggfly Hypolimnas bolina (Linnaeus, 1758) from Masirah Island, Oman and a summary of previous records from Arabia.

Abstract

On a visit to Masirah Island, Oman, observations were made of the striking butterfly Hypolimnas bolina, the Great Eggfly, at three locations over a four-day period in early October 2014. They were observed apparently making landfall at the south of the island and nectaring and basking in an overgrown orchard and hotel gardens in the north of the island. This species has previously been recorded from four other locations in Oman and two in the United Arab Emirates, with the most recent report prior to 2014 being in 1993. Three possible origins for the 2014 individuals are discussed: 1) immigrants from Socotra Island, either by natural dispersal or displacement by a tropical storm either directly over the sea or via southern Oman; 2) immigrants from the Indian subcontinent; and 3) accidental introduction with imported plants.

[FIGURE 1 & 2 OMITTED]

Introduction

Whilst on a visit to Masirah Island (off the southeast coast of Oman) from 4th to 7th October 2014, primarily to look for migrating birds, OC was surprised to find a very large, distinctively patterned butterfly that was not immediately recognised. Individuals were recorded at three sites. At two of those sites, other butterflies, initially taken to be examples of the male Diadem Hypolimnas misippus were also recorded. Photographs were taken and reference to Larsen (1984) on return to Abu Dhabi immediately showed that the 'mystery' species involved was the female of H. bolina, the Great Eggfly (also known as Giant Eggfly, Common Eggfly), and that the other butterflies associating with it were, in fact, not H. misippus but males of H. bolina. The observations made are detailed below and previous records of H. bolina in Oman and the United Arab Emirates are discussed, along with possible origins of the Masirah individuals. Photographs of the Masirah individuals are included but, unfortunately, only images of the females were obtained (Figs. 1 & 2).

Observations

The first example of H. bolina observed was at 1300 on 4th October at Ra's Abu Ra's (20.16[degrees]N, 58.63[degrees]E) the southernmost point of Masirah and 60km SSW from Hilf, the island's main settlement. It was first located using a telescope and appeared to be arriving from the sea. A little later another individual, more distant but seemingly the same species, was noted apparently making landfall in the same manner.

On 5th October at least three female H. bolina were seen in an overgrown orchard by the water treatment plant at Hilf near the northern tip of Masirah (20.619[degrees]N, 58.869[degrees]E). The insects were nectaring on shrubby Lantana bushes and basking in the early morning sun. Several males were also present and were observed on occasion to chase the obviously larger females. Insects nectared with their wings closed but also regularly flashed them open, revealing the uppersides. Butterflies were seen at this location daily until 7th October, on which date OC left Masirah. A prior early morning visit had been made to this site on 4th October; no butterflies were observed but it is quite possible they were present. Additionally, on 5th October another female was observed and photographed nectaring on the sunny edge of an overgrown Prosopis juliflora approximately 300m from the Lantana clump (Plates 1 and 2). This area was searched on subsequent dates until 7th October but butterflies were not seen in this area again.

Finally, on 5th October, at least six H. bolina (males and females) were located within the grounds of Masirah Island Resort, a recently developed hotel on the north-east side of the island (20.598[degrees]N, 58.903[degrees]E) and 4km ESE of the orchard at Hilf. They were actively nectaring on ornamental plants, in the company of small numbers of the Painted Lady Vanessa cardui. This location has been observed to hold migrant butterflies in previous autumns (for example up to 40 V. cardui in September 2009; OC pers. obs.).

As far as is known, there were no further reports of H. bolina on Masirah later in autumn 2014 or in 2015 (J. Eriksen, in litt.) although observer coverage is likely to be have been very low. In 2016, OC visited Masirah again from September 11th to 16th. Four full days were spent in the same sites outlined above but, despite specific searches being made repeatedly, no individuals of H. bolina were noted. Interestingly, however, at least two examples of male H. misippus were located, defending territories in the orchard at Hilf. No females were recorded.

Subspecies identification and distribution

Hypolimnas bolina is widely distributed in the Oriental and Australasian Regions, as well as on the islands of Madagascar, Mauritius and Socotra in the Afrotropical Region.

D'Abrera (1980) lists two major subspecies of H. bolina:

The nominate Hypolimnas bolina bolina (Linnaeus, 1758), found in the Australasian Region.

Subspecies Hypolimnas bolina jacintha (Drury, 1773), sometimes referred to as the Jacintha Eggfly, found from India to Taiwan (in the Oriental Region) and in Mauritius.

According to Corbet & Pendlebury (1992) and D'Abrera (1985), jacintha males are distinguishable by a "row of post-discal white spots on the recto surface". These spots are absent in the males of bolina.

An overlap of range between these two subspecies occurs in peninsular Malaysia and Singapore where both subspecies fly. Eighteen further subspecies of H. bolina are known, mostly from Australia and the Pacific Islands, but are not considered here.

Previous Records of H. bolina in Oman and the UAE

There are eight previous records of H. bolina from Oman and the UAE. These are mapped (Fig. 3) and summarised below.

A sighting of H. bolina was reported from Dhofar in Larsen & Larsen (1980) in October 1979 from 'above Rakhyut'. The butterfly was identified as a female but no specimen or photographs are available to ascertain the subspecies. Larsen (1983), relying on Elliott (1978) believed it to belong to subspecies jacintha.

Larsen & Pedgley (1985) reported records of H. bolina jacintha after being 'blown into Arabia' by tropical storm Aurora in August 1983. See discussion below, and Fig. 2.

H. bolina specimens were taken by Bjarne Skule from Wadi Ghul and Wadi Muaydin in Oman in May and June 1993 (respectively) (Hitchings & Skule, 2004). All of the specimens taken are female and cannot be identified to subspecies level.

H. bolina is represented in the national reference collection at the Natural History Museum in Muscat. Five specimens were collected during a survey visits by Michael D. Gallagher in Jaaluni in the Al Wusta Region of Oman (Hitchings, 2005). The dates vary from 1st September, 3rd October and 27th November 1992. No subspecies information is currently available.

Larsen & Pedgley (1985) reported records of H. bolina from four localities in Oman and the UAE. These observations were particularly interesting as it was surmised that the insects had been 'blown into Arabia' by tropical storm Aurora in August 1983 to four localities (see Figure 4): two in Oman (Seeb, Muscat and inland in the north-west of the country near the Buraimi oasis) and two in the UAE (Abu Dhabi island and near Al Ain Zoo). The Seeb record was a single individual, all others involved 'several'. It is interesting to note that Buraimi, Oman and Al Ain, UAE are adjacent to one another and that all records date from a very narrow time period (12th to 16th August) and within days of Storm Aurora crossing eastern Arabia westwards from the Indian subcontinent on 10th to 11th August. In this instance, based on analysis of specimens taken and, as would be expected given the origin of the storm concerned, the butterflies were identified as Hypolimnas bolina jacintha, and hence presumably originated from India.

Discussion

All of the photographs available from the 2014 Oman records are of female H. bolina and therefore not sufficient to permit identification to subspecies level. The closest known location to Masirah where H. bolina is resident is on the Socotra Islands, Yemen (Larsen & Larsen, 1980; Fric & Hula, 2013) some 1,000 kilometres southwest of Masirah but 390 kilometres from mainland Yemen and 450 kilometres from neighbouring Dhofar, Oman. Despite enquiries, it has not been possible to ascertain the subspecific identity H.bolina on Socotra where it appears to be rather poorly known.

Whilst it is presently impossible to go beyond informed speculation, it is interesting to consider the possible origin of the examples of H. bolina on Masirah.

If Socotra was the source of the Masirah butterflies, three possibilities may account for this:

1. The butterflies reached Masirah aided by the prevailing south-westerly winds that blow from April to September or early October over the northern Indian Ocean (Fisher & Membery, 1988). Evidence that this may be the case are the two individuals observed apparently arriving at the southern tip of the island on 5th October. However, such winds are an annual and marked phenomenon across the northern Indian Ocean and, if butterflies are prone to displacement by such 'normal' conditions, one might expect them to be more regular on Masirah and southern Oman in general.

2. They were blown from to Masirah from Socotra by a tropical storm. As Hypolimnas bolina jacintha has been recorded as storm-blown individuals to Oman and the UAE in 1983 (Larsen & Pedgley, 1985) it is reasonable to consider this possibility. Furthermore, in 2014 the North Indian Ocean Cyclonic Storm Nanauk, tracked over Socotra and north-eastwards from 7th to 14th June (see Figure 6). The five month interval between the storm and the sightings would be ample time for H. bolina to establish breeding populations. However, if this is the case, it must be noted that there have been no further sightings on Masirah Island in 2014 and 2015 (although this may be a function of a lack of observers) and the species, although searched for, was apparently absent by September 2016. Hence, any breeding population, if indeed one was established at all, did not persist.

3. They migrated from Socotra to mainland Yemen/Dhofar and then on to Masirah. Records of this species in southern Oman indicate this is a possibility. However, it is likely that many individuals would need to arrive in southern Oman to account for the handful observed on Masirah and there have been no records in southern Oman since 1980. Again, however, a lack of sightings in 2014 may simply reflect the lack of observers.

Possibilities for an origin other than Socotra include:

4. The butterflies had a natural Indian origin, arriving on Masirah at some point prior to October 2014.

5. The butterflies were introduced with imported plants for the gardens, for example at the recently constructed Masirah Island Resort.

Possibility 5 is difficult to evaluate without knowing the identity and source of ornamental plants used on Masirah, but it offers no explanation for the apparent arrival of individual H. bolina by sea, from the south, as observed in this instance. Possibility 4 is hard to discount in the absence of knowledge of the subspecific identity of the butterflies but seems unlikely, at least in the six month period prior to the sightings, given the prevailing wind direction over the northern Indian Ocean and the absence of any storm on a similar track to Storm Aurora.

It has been recently established that the dragonfly Pantala flavescens crosses the entire tropical Indian Ocean routinely (Anderson, 2009) from India (or possibly from even further to the north and east; Hobson et al, 2012) to East Africa, using north-east tail winds established as the Inter-Tropical Convergence Zone passes south from mid-October onwards. For this reason, we deem the possibility of H. bolina arriving on Masirah in autumn 2013 or the winter following this and then colonising, at least temporarily, is at least plausible.

[FIGURE 6 OMITTED]

Acknowledgements

We are extremely grateful to Gary Feulner for completing a comprehensive edit of a first draft of this paper and for many insightful comments that have greatly improved the text. Jens Eriksen provided information on his observations on Masirah in late autumn 2014 and subsequently. Richard Porter, Vladimir Hula and Kay van Damme all promptly answered queries concerning H bolina on Socotra. Gillian Ensor accompanied OC during both visits to Masirah and exhibited both enthusiasm and patience in abundance.

References

Anderson, C. 2009. Do Dragonflies migrate across the western Indian Ocean? Journal of Tropical Ecology 25:347-358.

Corbet, A.S. & Pendlebury, H.M. 1992. The Butterflies of the Malay Peninsula (Fourth Revised Edition). United Selangor Press. 595 pp.

D'Abrera, B. 1980. Butterflies of the Afrotropical Region. Lansdowne Press Pty Ltd. 593 pp.

D'Abrera, B. 1985. Butterflies of the Oriental Region, Part II. Lansdowne Press Pty Ltd. 532 pp.

Fisher, M. & Membery, D.A. 1998. Climate. In Ghazanfar, S.A. and Fisher, M. (eds.) Vegetation of the Arabian Peninsula. p5-38.

Fric, Z. & Hula, V. 2013. Zizula hylax (Fabricius, 1775) a new butterfly species for Socotra (Lepidoptera: Lycaenidae). SHILAP Revta. Lepid. 41: 571-575.

Hitchings, V.H. 2005. Distribution Maps and Flight Phenograms of the Butterfly Specimens from the Oman Natural History Museum Collection. Report to the Oman Natural History Museum, Muscat.

Hitchings, V.H. & Skule, B. 2004. Distribution Maps of the Butterflies of Oman: From the Collection of Bjarne Skule. Report to the Oman Natural History Museum, Muscat.

Hobson, K.A., Anderson, R.C., Soto, D.X. & Wassenaar, L.I. 2012. Isotopic Evidence That Dragonflies (Pantala flavescens) Migrating through the Maldives Come from the Northern Indian Subcontinent. PLoS ONE 7(12): e52594. doi:10.1371/journal.pone.0052594

Larsen, T. & Larsen, K. 1980. Butterflies of Oman. John Bartholomew and Sons, Edinburgh. 80 pp. Available online at:http://www.enhg.org/Home/Publications/eBooks/ButterfliesofOman.aspx.

Larsen, T.B. 1984. Butterflies of Saudi Arabia and its Neighbours. Stacey International, London. 160 pp.

Larsen, T.B. & Pedgley, D.E. 1985. Indian migrant butterflies displaced to Arabia by monsoon storm 'Aurora' in August 1983. Ecological Entomology 10:235-238.

by Victor Hitchings and Oscar Campbell

Victor Hitchings

248 Abergele Road

Old Colwyn, LL29 9YH, UK.

Email: vic_hitchings@hotmail.com

Oscar Campbell

c/o British School Al Khubairat,

PO Box 4001,

Abu Dhabi, UAE.

Email: ojcampbell25@yahoo.com
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Author:Hitchings, Victor; Campbell, Oscar
Publication:Tribulus
Article Type:Report
Geographic Code:7OMAN
Date:Jan 1, 2016
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