Recent record of the Phalakron Plain Plushblue Flos apidanus phalakron (Lepidoptera: Lycaenidae) in South Sumatra after 91 years break

An individual of Phalakron Plain Plushblue Flos apidanus phalakron was observed and phtographed on 17 March 2020 at campus Sriwijaya University, Indralaya, South Sumatra province. In South Sumatra, this butterfly only known from a historical record in 1929. The recent observation of Flos apidanus phalakron in Indralaya represent a new record for South Sumatra province after 91 years break.


Introduction
Family Lycaenidae (lycaenid butterflies) are large group of butterflies comprise more 5.000 species (Holloway et al., 2012). These groups are small to medium sized butterflies, and many are rare or have localized distribution (Ek-Amnuay, 2012). Generally, the males are more highly coloured than females (Fleming, 1983). Many more undoubtedly remain to be discovered as most of the tropical species spend their entire lives undetected in the rainforest canopy (Hoskins, 2015).
Flos is one genus of family Lycaenidae that having a broad dark band on underwing and hindwing without a tail or with a weakly dentated or rounded tail at the marginal border (Ek-amnuay, 2012). There are six species of genus Flos in Sumatra, including Flos apidanus, Flos anniella, Flos bungo, Flos diardi, Flos fulgida and Flos morphina (d'Abrera, 1986;Savela, 2020). This genus under subfamily Theclinae, a large subfamily of family Lycaenidae, with many species of varying patterns and colour (Kirton, 2014). Subfamily Theclinae occurs on and continents and in all habitats, including moors, grassland, deciduous woodlands and tropical rainforests (Hoskins, 2015).
As the second largest island of Indonesia, Sumatra has rich animal diversity (Whitten et al., 2000). The island had at least 756 species of butterflies (de Niceville & Martin, 1896), but this number must be increased recently. The Plain Plusblue Flos apidanus is one species of butterfly that occur in Sumatra (d'abrera, 1986). In 1914, few specimens of Flos apidanus from Sumatra were described as a distinct subspecies with original name Arhopala apidanus phalakron (Fruhstorfer, 1914). A comprehensive study of the genus Arhopala group of family Lycaenidae redesigned Amblypodia apidanus to Flos apidanus, then Flos apidanus phalakron was named for this Sumatran butterfly (Evans, 1957).
This paper describe a recent finding of Flos apidanus phalakron in Indralaya, South Sumatra province. The occurrence of Flos apidanus phalakron from Indralaya is represent a recent record in South Sumatra province after 91 years break.

Materials and Methods
On 17 March 2020, a lycaenid butterfly was observed and photographed at arboretum of campus Sriwijaya University, Indralaya (03°14'29''S, 104°39'54''E). Unfortunately, the butterfly is unable to caught and no specimen was preserved. However, distinct morphological features of the butterfly were clearly seen from some pictures taken from prosumer Fuji Film Pinefix S1 with 50x zoom lens camera. The butterfly was identified to species level with appropriate butterfly guides.

Results and Discussion
The lycaenid butterfly found at campus of Sriwijaya University in Indralaya has small-medium butterfly size (c. 20 mm of forewing length, and 34 mm of wingspan), hindwing with weakly dentated, underwing is pale yellowish brown, with a dark reddish brown area at bases of hindwing, forewing discal and postdiscal bands evenly curved, hindwing with irregular discal gray bands from midcosta to the mid dorsum and darker towards the borders (Figure 1). These characters are fitted well to characters of Flos apidanus in selected references (d'Abrera, 1986;Corbet & Pendlebury, 1992;Khoon, 2010;Ek-Amnuay, 2012).

Figure 1. An individual of Flos apidanus phalakron found on 17 March 2020 at campus Sriwijaya University in Indralaya,
South Sumatra.

Recent observation of Flos apidanus phalakron at the campus of Sriwijaya
University in Indralaya is a recent record of this subspecies in South Sumatra province after 91 years break. This subspecies different from other subspecies by having much duller with the purplish cast of the hindwing missing, and the tornus of the hindwing appear to extensive green metallic green scaling (d'Abrera 1986). This subspecies has been known occur in Palembang based on a historical record in 1929 (Toxopeus 1929), but no information available since this report. The host plants known for Flos apidanus are plant from family Lythraceae and Myrtaceae (Robinson et al. 2001). The plants from both families are relatively able to find in Sumatra. Further study to monitoring the occurrence of Flos apidanus phalakron in Sumatra is needed, to looking at spatial distributions and trends of population in the future.

Conclusion
Recent observation Flos apidanus phalakron at campus Sriwijaya University in Indralaya is a rediscovery record in South Sumatra province after the first time reported in 1929. This recent observation is represent a second record for South Sumatra after 91 years break.