Onitis assamensis Biswas, 1980

Karimbumkara, Seena Narayanan & Priyadarsanan, Dharma Rajan, 2024, Study on the genus Onitis (Coleoptera: Scarabaeidae: Scarabaeinae) of the Indian Subcontinent, with three new species from India, European Journal of Taxonomy 956, pp. 1-61 : 6-8

Onitis assamensis Biswas, 1980

Figs 1 , 4A–D , 17

Onitisassamensis Biswas, 1980: 339 (original description).

Onitis assamensis – Gupta et al. 2015: 1037 (checklist). — Schoolmeesters 2022 (online catalogue).

Differential diagnosis

Onitis assamensis and O. naviauxi differ from each other in the number of teeth on the anteriomedian ridge of the protibia in the male. Clypeal carina short in male of O. assamensis and O. naviauxi while it is longer in female; clypeus in female pointed in both species; metasternal shield hairy in males and smooth in females. In the original description of O. assamensis the frontal carina is considered entire, but on observing the specimen in detail, it is confirmed that it is interrupted due to the placement of tubercle on it. The teeth on the infero-internal ridge in the profemur is a very prominent character of the species and the arrangement of teeth, their number and size may vary with individuals. In a specimen we collected, an extra small tooth was present near the femoro-tibial joint on one of the fore legs.

Material examined

Holotype

INDIA • ♀; Assam, Kaziranga National Park ; 21 Dec. 1972; A.K. Ghosh leg.; from rhinoceros dung; ZSIM Regd. No. A1/4397 .

Additional material (15 specimens)

INDIA • 8 ♂♂, 7 ♀♀; Assam, Kaziranga National Park ; 21 May 2019; Priyadarsanan Dharma Rajan & Karimbumkara Seena Narayanan leg.; hand–picked, rhinoceros dung; AIMB AIMB/Co/Sc1000001 to 1000015 .

Description

MEASUREMENTS (in mm). TL=21.5–24.8; BW =10.7–12.5; PL=8.5–11; PW= 10.5–13.5; EL=10.5– 12.5; HL= 5–6; HW=5.5–6.8.

Male

Body shiny green or bronzy, broadly oval. Head rounded, clypeus straight in the middle anteriorly, finely rugose with scattered punctures; clypeal carina short, rugose behind; frontal carina almost straight, narrowly interrupted in the middle by the placement of a strong conical blunt tubercle; vertex sparsely punctured, elevated towards the eyes with a depression in the middle devoid of any punctures. Pronotum with small, close dense punctures between the basal foveae, punctures larger and less close anterior to the foveae, finer and sparse anteriorly and at the sides; basal foveae oval, deep, connected by a bordered base; scutellum triangular visibly large. Elytra broadly curved at the sides; striae deep, broader at the base, narrow and smooth towards the tip; elytral intervals smooth without punctures, sutural interval slightly convex. Pygidium margined, lesser sheen, imperceptibly punctured. Metasternal shield with minute punctures, front angles with minute granules and fine yellow hairs; sides of metasternum with reddish hairs, densely granular. Fore legs with rows of reddish long hairs or setae on the ridges; a strong curved tooth on the anteromedian ridge of profemur with a minute oblique denticle near the base; protibia with four distantly placed external teeth, the infero-medial ridge with 6–7 teeth, small proximally and stouter distally; mid femur unarmed; hind femur with a strong curved lateral tooth towards the apex.

AEDEAGUS (in mm) ( Fig. 4A–D ). LP=3.6, Lp =2.86; BP=1.86, BpB=1.43, BpT= 0.71. Phallobase longer than parameres, broader at base and further tapers, becomes blunt and slightly curved at the tip. Phallobase slightly broader at the base.

Female

Body greenish, broadly oval, not very convex; head sub triangular, frontal carina entire with a tubercle. Clypeal carina long and curved placed almost midway between the clypeal margin and the frontal carina; clypeus parabolic, rugulose. Pronotum strongly and closely punctured; front angles sharp; basal foveae rounded. Elytra: dull, striae shallow and broad, intervals flat, not perceptibly punctate. Ventral surface: metasternum flat, smooth with two deep pits behind and a shallow longitudinal groove between; sides of metasternum closely granular and hairy. Pygidium without hair, slightly shining and coarse; legs unarmed.

Distribution

India: Assam ( Biswas 1980; Gupta et al. 2015; Schoolmeesters 2022).

Remarks

A single female specimen of O. assamensis was collected by Biswas (1980) from rhinoceros dung and described as the holotype. During our visit to Kaziranga National Park, we have collected 15 specimens of the species of which eight were males and seven females. The rarity of the species mentioned by Biswas can be attributed to the winter in December when he had made the collection. The species was common and active in May (pre-monsoon), when we collected them at the same location. We have described the male of Onitisassamensis which had never previously been discovered or described.

Figures

Fig. 1. Onitis assamensis Biswas, 1980, ♂ (A–D), AIMB/Co/Sc1000001; ♀ (E–F), AIMB/Co/ Sc1000009. A. Habitus, dorsal view. B. Habitus, ventral view. C. Protibia. D. Pygidium. E. Habitus, dorsal view. F. Habitus, ventral view. (Images: AIMB)

Fig. 4. A–D. Onitis assamensis Biswas, 1980, Aedeagus, lateral, dorsal, ventral and apical views, AIMB/ Co/Sc1000001 (images: AIMB). E–F. O. naviauxi Cambefort, 1988, lateral and dorsal views, MNHN EC4807, (images: Antoine Mantilleri, MNHN). G–J. O. bordati Cambefort, 1988, aedeagus; lateral, dorsal, ventral and apical views, AIMB/Co/Sc1000016, (images AIMB). K–N. O. siva Gillet, 1911, aedagus, lateral, dorsal, ventral and apical views, AIMB/Co/Sc1000704, (images: AIMB).

Fig. 17. Map showing the distribution of OnitisassamensisBiswas, 1980; O. bhomorensis sp. nov.; O. bordatiCambefort, 1988; O. brahma Lansberge, 1875 and O. castaneus Redtenbacher, 1848 in the Indian Subcontinent.