New additions to the larval food plants of Sri Lankan butterflies (Insecta: Lepidoptera: Papilionoidea)

Larval food plants (LFPs) of Sri Lankan butterflies have been well documented recently with the aid of studies done by numerous researchers. In this paper, we present further records, 118 LFPs used by 83 butterflies and 145 plant-butterfly combinations. LFPs of Lethe dynsate and Potanthus pseudomaesa pseudomaesa are reported for the first time in Sri Lanka. Important observations, possible LFPs and LFP preferences of rare and threatened butterfly species, are discussed. This information on plant-butterfly interactions will play an important role in conservation management of both plant and butterfly species.


INTRODUCTION
The knowledge on the natural history of Sri Lankan butterflies has been increasing rapidly over the past two decades, mainly due to the increase in the numerous field studies carried out by various researchers on butterflies, including their early stages, that had been published as research papers, detailed books, field guide books, leaflets and as other social media material (Gamage 2007;Jayasinghe 2014;Jayasinghe et el. 2015Jayasinghe et el. , 2020van der Poorten & van der Poorten 2016, 2018. The availability of information has led many amateur naturalists to get interested and actively involved in the study of butterflies and now even contribute to the development of knowledge database on butterflies of Sri Lanka.
Early stages of Sri Lankan butterflies have been described in detail in several recently published research papers (van der Poorten & van der Poorten 2011a,b, 2012a,b,c, 2013a,b, 2014Gunawardana et al. 2015;Priyadarshana et al. 2015;Herath et al. 2020), which provide information on their larval food plants (LFPs) as well. A research article focused on LFPs on Sri Lankan butterflies (Jayasinghe et el. 2014) provided 480 species of LFPs for 207 species of butterflies out of the 245 species known in the country during that time. Further, it documented 785 plant -butterfly combinations. Since then three more butterfly species have been added to the Sri Lankan inventory (van der Poorten & van der Poorten 2016, 2018, and a few more LFPs had been recorded. Further studies carried out during the last few years revealed some more undocumented LFPs of Sri Lankan butterflies, which are presented in this paper. Some plant species which were not identified up to the species level in previous publication (Jayasinghe et al. 2014) are identified here as well. Recent nomenclatural and systematic changes in LFPs which were already documented in aforementioned publications are also addressed.

MATERIALS AND METHODS
The data presented in this paper is primarily based on studies carried out during 2014-2019 by the authors. Field studies were conducted throughout the country in various habitats, including the northern and eastern regions of the country, which were not studied for decades due to their inaccessibility. Materials and methods adopted for field observations, field notes, data collection, photography, lab works, and identification of butterfly species and plant species follow Jayasinghe et al. (2014). The lab rearing studies were carried out in Soragune (6.747N & 80.893E) Badulla District, Malwana (6.968N & 80.006E) Gampaha District and Kandumulla (7.075N & 80.071E) Gampaha District. Rearing of hill country species was restricted to Soragune, since the temperature and other climatic conditions are suited best out of all the three locations and due to relatively easy accessibility to collect fresh food material regularly from the field. Low country species, both from the wet zone and dry zone were reared at all the three locations, but rearing of northern species were mainly restricted to Malwana. Apart from identification from guide books, some plant species had to be confirmed by studying herbarium sheets at the National Herbarium at Peradeniya and online available herbarium sheets at K, BM, E, and L (Thiers 2020).
All the species of plants presented in this paper are confirmed LFPs in Sri Lanka. Here we consider a species as a confirmed LFP, when the butterfly larvae reared on it until maturity, or the early stages and egg laying behaviors observed regularly in the field on a given plant species. Even the larvae found on certain plants, if they were unable to complete the larval stage on those plants are not considered as confirmed LFPs. We observed that certain butterfly species (i.e., Acraea terpsicore) are trying to test new species of LFPs, but are not always successful. Certain butterfly larvae were found on non LFPs in the field, probably while they are moving from one plant to another or accidentally fell off. Species such as Delias eucharis and Papilio clytia lankeswara were observed shifting their LFPs for pupation. The data presented here, other than the studies carried out by the authors were included only if they were verified by detailed photographs and the plant species especially were identified by the authors based on information provided by those individuals.
Nomenclature of the butterflies follows van der Poorten & van der Poorten (2016). Classification and nomenclature of angiosperms, which had been subjected to dramatic changes due to recent molecular phylogenetic studies are based on (POWO 2019), and (WCSP 2020) Early stages of the remaining 23 species are yet to be discovered in Sri Lanka, though some of these indigenous species have been reared in other countries (Nitin et al. 2018). Seven species and five subspecies out of these 23 are endemic to Sri Lanka. Even though the LFPs of these species are not yet confirmed, clues for some species were observed during the field studies. Mycalesis rama (Moore, 1892) was most frequently observed among Ochlandra stridula in lowland rainforests and very rarely go beyond these bushes while mating pairs were observed in Yagirala forest reserve (6.376 N & 80.169 E) among these bushes. Arhopala ormistoni Riley, 1920 is a very rare butterfly species which was originally described from Nakiyadeniya in southern wet zone (Woodhouse 1949) and not known for decades until its appearance in a disjunct population at the eastern intermediate zone (van der Poorten & van der Poorten 2016). One of its closely allied species Arhopala bazaloides lanka (Evans, 1957) is using a Dipterocarpaceae species as its sole LFP, initially, which was described as early stages of A. ormistoni by an mis-identification (van der Poorten & van der Poorten 2013a). An unusual population of more than 50 individuals of A. ormistoni was found recently in the catchment area of Namal Oya reservoir (7.321N & 81.521E). The only plant species belonging to the family Dipterocarpaceae in this micro-habitat is confirmed during this study as Vatica obscura, the species that was tentatively identified previously as an egg-laying plant of this butterfly (van der Poorten & van der Poorten 2016). Though the adult individuals of endemic Udara singalensis (R. Felder, 1868) and Thoressa decorata (Moore, 1881) are quite regularly seen, there are no any clues about their LFPs. Mostly, males of these species are seen in the field, but we never had a chance to follow females who are searching for LFPs. The remaining endemic species Tajuria (Manders, 1903), which is also restricted to the same area. We were able to find this very rare, micro-habitat specific plant by tracing the butterflies who are looking for suitable plants for egg laying and we observed early stages at all the three locations. This incident reveals the importance of conserving the LFPs for the conservation of butterflies. The preferred LFP of the Critically Endangered butterfly Catochrysops panormus panormus (C. Felder, 1860), Flemingia macrophylla, was considered to be possibly extinct until it was rediscovered during this research. Fortunately, this species is now being introduced as a hedge plant for low country tea estates by the Tea Research Institute (Rajika Gamage pers. comm. 17.iv.2018), but whether these plants are exactly from the native population or a cultivar and whether the butterfly larvae are feeding on them, is yet to be discovered.

RESULTS & DISCUSSION
Out of the known details of 223 butterfly species, 47 of them are reported having a single LFP each. This includes nine endemic species and 20 endemic subspecies. Most of them appear to have a sole LFP, but there is a possibility to find more LFPs for some of these species. At the other extreme, Neptis hylas varmona Moore, 1872 is the most polygamous species in Sri Lanka. It uses 46 species of LFPs belongs to six families. Euploea core asela Moore, 1877 ranked for the second place by using 30 LFPs, but those plants belong only to two families. Zesius chrysomallus Hübner, 1821 seems to feed on any plant, where the Red Weaver Ants Oecophylla smaragdina Fabricius, 1775 are colonized. Butterflies that use the highest number of LFPs are listed in table 1. The exotic plant Axonopus compressus (Sw.) P. Beauv. has been reported to be used by 14 species of butterflies. It is interesting that many Poaceae species are shared by a high number of butterfly species (Table  2). Three-hundred-and-forty-four plant species from the whole LFPs list are not shared by two or more butterfly species. Most of the reported LFPs belong to the family Fabaceae (Table 3).
This information on LFPs of Sri Lankan butterflies can be used for habitat conservation-oriented management strategies, which will enhance the conservation of other flora and fauna as well. Further studies on the life history of targeted species are required for the unknown 23 species of butterflies which consist of very rare and / or endemic species. These studies should be aimed at revealing the reasons for their scarcity, which are required to ensure their future survival.   Table 3. Number of LFP species in highest ranked families.

Larval food plants of Sri Lankan butterflies
Jayasinghe et al. www.threatenedtaxa.org

Annexure 1. Newly recorded LFPs of Sri Lankan butterflies. DS-Distribution status | Ex-Exotic | En-Endemic | In-Indigenous | l-leaves | il-immature leaves | ml-mature leaves | fl-flower | flbflower buds | fr-fruit | st-stem, se-seeds | br-bracts | PC-personal communication | LA-Lasantha Aberathna | NC-Nuwan Chathuranga | KW-Kalana Wijesundara | ND-Narmadha Dangampola | SG-Sujeewa Gunasena | CU-Chathura Udayanga | GR-Gehan Rajiv.
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