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''Narycius opalus'' is a flower chafer beetle that is endemic to the Western Ghats of India. It is the sole species in the genus. The adult male has a prominent projection on the head, while the female has a much shorter horn. This structure is probably the result of 
This beetle is about 2 to 2.5 cm long and 1.3 cm wide. The distinctive cephalic horns may be nearly two-thirds the length of the thorax and abdomen combined. The surface is matt and the elytra are minutely pitted along lines. The
Museum specimens
Cetoniinae Beetles of Asia Beetles described in 1835 {{Cetoniinae-stub
sexual selection
Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex ( ...
, as in similar beetles. The adult beetle is shiny iridescent rose ranging to green, with intermediates.
The species was described and given its name by Henry Dupont who also described the females as a separate species, named ''Narycius olivaceus''. Westwood named the green color form as ''Narycius (Cyphonocephalus) smaragdulus''.
This beetle is about 2 to 2.5 cm long and 1.3 cm wide. The distinctive cephalic horns may be nearly two-thirds the length of the thorax and abdomen combined. The surface is matt and the elytra are minutely pitted along lines. The prothorax
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum ( dorsal), the prosternum ( ventral), and the propleuron ( lateral) o ...
and scutellum have pits that are irregularly placed. The upper edges of the cephalic horn are nearly straight and parallel and the expand towards the end and the tips are inwardly curving. The prothorax is convex above and is broadest at the middle. The female has a much shorter cephalic horn and colour variants exist. The confusion arising from the sexes being treated as species was resolved only after a pair ''in copula'' was collected by the entomologist T.R.D. Bell.
The species has been recorded from across the Nilgiris, the Biligirirangan Hills, and the Western Ghats.
References
External links
Museum specimens
Cetoniinae Beetles of Asia Beetles described in 1835 {{Cetoniinae-stub