Review of the Orphninae (Coleoptera: Scarabaeidae) of Sri Lanka, with description of a new species of genus Orphnus Macleay, 1819

The scarab beetles of the subfamily Orphninae (Coleoptera: Scarabaeidae) from Sri Lanka are reviewed. Four species of the genus Orphnus Macleay, 1819, are recorded from the island: O. bicolor (Fabricius, 1801), O. parvus (Wiedemann, 1823), O. mysoriensis Westwood, 1845, and O. medvedevi sp. nov. Lectotypes are designated for the three former names. Synonymy of O. detegens Walker, 1859, and O. scitissimus Walker, 1859, is discussed. Keys, illustrations of habitus and male genitalia, and distributional record maps are given for all species.


Introduction
Scarab beetles of the subfamily Orphninae Erichson, 1847, are mostly distributed in the southern continents. The nominative and most speciose genus of this subfamily, Orphnus Macleay, 1819, has its centre of diversity in the Afrotropics. However, six nominal species including the type species of the genus, O. bicolor (Fabricius, 1801), are known from Southeast Asia including the island of Sri Lanka. Three species of Orphnus have been described from Sri Lanka: O. nanus Westwood, 1845, O. detegens Walker, 1859, and O. scitissimus Walker, 1859. Later, Arrow (1912 suggested that all these names are synonyms of two Indian species, O. parvus (Wiedemann, 1823) (the former name) and O. mysoriensis Westwood, 1845 (the two latter names).
The literature on Asian Orphninae is limited to primary sources with brief diagnoses of the species and catalogues, and provides a poor foundation for species identification. The shape of the aedeagi and internal sac armature, the most reliable diagnostic characters in Orphninae, were not described or illustrated by past authors.
Reasonable material on Orphninae from Sri Lanka had been accumulated in museums but has never been taxonomically examined. In this material, we recognized four species based on the external morphology and morphology of the male genitalia. Because of the inadequate original descriptions, it was necessary to compare this material with primary types. As a result, we found that the island is inhabited by four species, including two species not recorded from Sri Lanka before: O. bicolor and an undescribed species, a putative endemic of the island. The aim of the present contribution is to provide a taxonomic revision of the Orphninae from Sri Lanka, including lectotype designations for published names, description of the new species, re-evaluation of the synonymies proposed by Arrow, detailed illustrations of the male genitalia of all species, as well as a key to species and distribution maps.

Material and methods
Morphological terminology follows Frolov et al. (2016). Preparation of specimens, digital images, and locality map follow Frolov et al. (2017). Labels of the type specimens are cited verbatim with separate labels separated by a slash '/'.

Differential diagnosis
Orphnus mysoriensis is similar to O. medvedevi sp. nov. in having the pronotum with a more or less developed tubercle on the base medially and the endophallus with one group of spinules. It differs from the latter in body length (8.0-10.0 mm, as opposed to 4.6-6.0 mm in O. medvedevi sp. nov.), spinules of endophallus as a rather dispersed group of more than 10 spinules (as opposed to a compact cluster consisting of less than 10 spinules in O. medvedevi sp. nov., Fig. 1G vs Fig. 3G), and tubercle on the base of pronotum normally with two punctures (as opposed to always smooth tubercle in O. medvedevi sp. nov.).

Variation
Body length of the examined specimens varied from 8.0 to 10.5 mm (males) and from 7.0 to 9.0 mm (females). Head and pronotum armature in males varied from well-developed with long lateral pronotal processes and frontoclypeal horn ( Fig. 2A) to excavated pronotum with gibbosities aside of the excavation and frontoclypeal tubercle (Fig. 2C), with intermediate variants (Fig. 2B).

Distribution
The species is distributed rather widely on Sri Lanka except for the eastern part (Fig. 1H).

Differential diagnosis
Orphnus medvedevi sp. nov. is similar to O. mysoriensis in having the pronotum with more or less developed tubercle on base medially and endophallus with one group of spinules. It differs from the latter in shorter body (4.6-6.0 mm, as opposed to 8.0-10.0 mm. in O. mysoriensis), spinules of endophallus as a compact cluster consisting of less than 10 spinules (as opposed to a rather dispersed group of more than 10 spinules in O. mysoriensis, Fig. 3G vs Fig. 1G), and tubercle on the base of pronotum always smooth (as opposed to having normally two punctures in O. mysoriensis).
Clypeus. Wide, with convex anterior margin, rounded laterally, finely crenulate. Genae small, not protruding past eyes. Frontal suture indistinct. Clypeus with long, slender horn directed upwards and slightly curved backwards apically. Dorsal surface of head finely punctate. Labrum deeply sinuate in the middle, distinctly protruding past clypeus.
pronotum. With rounded sides, about 1.5 times as wide as long, with deeply concave disc, conical lateral processes aside excavation, and smooth, rounded tubercle medially near base. Anterior angles acute; posterior angles rounded, indistinct in dorsal view. Pronotum bordered on anterior margin and base. Lateral margins with long, sparse, brown setae. Sides irregularly punctate with round punctures separated by 3-5 puncture diameters.
elytra. About as long as wide, with distinct humeral humps, widest in middle, lateral margins slightly rounded in basal half. First (sutural) stria distinct, as feebly impressed groove with row of punctures. Other stria before humeral humps as rows of round setiferous punctures, separated by more than 3 their diameters except for base of elytra. Elytral intervals covered with minute punctures.

Wings. Macropterous.
legs. Protibiae with 3 outer teeth. Lateral margin basad of outer teeth not crenulate. Apical spur of protibia absent. Left protarsus absent. Middle and hind legs similar in shape; metafemora and metatibiae about ⅛ as long as the mesofemora and mesotibiae. Mesotibia and metatibiae somewhat triangular with 2 apical spurs, inner margin almost straight, with 1 transverse keel. Upper spur of tibiae as long as two basal tarsomeres. Claws ⅓ length of apical tarsomere. Femora almost impunctate.

Female
Female (Fig. 3H) differs from the male in having a relatively smaller pronotum without armature, frontoclypeus without process, and prothoracic spur present.

Variation
Body length of the paratypes varies from 5.9 to 4.6 mm (males) and 4.7 to 6.0 mm (females). Some of the paratypes have darker elytra. Head and pronotum armature in males paratypes varies from relatively well-developed, similar to that of the holotype, to excavated pronotum with gibbosities beside the excavation and frontoclypeal tubercle (Fig. 3C), with intermediate variants (Fig. 3B).

Distribution
The species is known from one locality in north-western Sri Lanka (Fig. 3I).

Differential diagnosis
Orphnus bicolor is similar to O. parvus in having the pronotum without tubercle on base medially and endophallus with a few groups of spinules. It differs from the latter in having the parameres in dorsal view with small but distinct notches basad of the lateral teeth (

Variation
Body length of the examined specimens varies from 7.5 to 9.0 mm (males) and 8.6 mm (female).

Distribution
The species was described form "East India". In Sri Lanka, it is known from two rather distant localities in the centre and on the southern coast (Fig. 4I).

Differential diagnosis
Orphnus parvus is similar to O. bicolor in having the pronotum without a tubercle on base medially and endophallus with a few groups of spinules. It differs from the latter in having the parameres in dorsal view without notches basad of lateral teeth (Fig. 5G), shorter parameres (about 0.5 length of phallobase [ Fig. 5E] as opposed to 0.7 length of phallobase in O. bicolor [ Fig. 4E]), and abdominal sternite 8 medially as long as sternites 4-7 combined (as opposed to sternite 8 medially distinctly longer than sternites 4-7 combined in O. bicolor).

Distribution
The species is distributed rather widely throughout Sri Lanka except for the north-eastern part (Fig. 5J).

Discussion
Since the shape of aedeagi and internal sac armature were not utilized by the previous authors dealing with Asian Orphninae, we decided to re-examine the types of the two species described by Walker from Sri Lanka but later synonymised by Arrow (1912). Walker (1859a, 1859b) described two species of Orphnus, O. detegens and O. scitissimus. In the original description of the former, males and females are mentioned. However, only one specimen of the type series was found in the BMNH collection. This specimen ( Fig. 2E-F) is a male designated here as the lectotype. It agrees with the original description of O. detegens and the type and other material of O. mysoriensis and therefore we can confirm synonymy proposed by Arrow (1912).
Despite every effort was made to trace the type (types) of O. scitissimus in the institutions that may house Walker's collection, we failed to find any specimens that could be considered as the types. The original description was apparently based on a female and fits the diagnosis of O. mysoriensis, although it is very brief and does not include diagnostic characters of this species. The size indicated (8.5 mm) agrees with O. mysoriensis but not with O. medvedevi sp. nov., which is significantly smaller. Therefore, we follow Arrow, who might have seen Walker's specimens, and consider of O. scitissimus as a synonym of O. mysoriensis.
Our results show that the fauna of the Orphninae of Sri Lanka, despite the relatively small size of the island, is comprised of four species and is comparable to the fauna of the whole mainland Asia which is inhabited by five species of Orphnus occurring from Northern India to Vietnam (Arrow 1912). Three of the four species also occur in India which can be explained by the relatively recent land connection of Sri Lanka and the Indian Peninsula.