We found a few of these stag beetles (hirata-kuwagata) when we were out beetle hunting last night. It was great to find a male and female feeding together on tree sap. We brought them home to take some photographs and then, this morning, I took them back to the same place to release them.
This species of stag beetle shows a lot of variation in the serrations on its mandibles, but the main identification feature is a split labrum (“upper lip”).
I found a very interesting scientific paper on the problem of imported and released pet stag beetles interbreeding with the native populations: here (pdf file).
(aka. Serrognathus platymelus)
Hirata stag beetle = hirata-kuwagata
Location: Tsurugidake Natural Park, Kurate, Fukuoka-ken (google map)