Mandibles of the Dorcus rectus species of beetle

''Dorcus rectus'', the little stag beetle, is a species of

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

s in the family Lucanidae. It can be found in

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

(Liaoning),

Korea Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, with North Korea (Democratic People's Republic of Korea) comprising its northern half and South Korea (Republic o ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...

and

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

.Catalogue of Life: 2019 Annual Checklist
/ref> These beetles have a distinctive red shell that separates them from ''

Dorcus curvidens ''Dorcus curvidens'' is a species of stag beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other ...

''. Males of this species have been observed to have mandible

trimorphism {{Expert needed, biology, talk=Trimorphism#This line seems a misreading of Wallace, reason=Darwin might have misread Wallace, date=December 2018 In biology, trimorphism is the existence in certain plants and animals of three distinct forms, especial ...

, a characteristic that has only been described in two species of Lucanidae—with the other one being

Odontolabis cuvera ''Odontolabis cuvera'', the golden stag beetle, is a beetle of the family Lucanidae, stag beetles. Etymology The Latin species name ''Cuvera'' comes from a mythical king of riches (Kubera or "Kuvera") who lived in the Himalayas.E. A. D'AbreThe ...

—"and a small number of other invertebrates" as of 2017. The mandibles are used by males as weapons.

References

Lucaninae Beetles of Asia Insects of Japan Taxa named by Victor Motschulsky Beetles described in 1857 {{Lucanidae-stub