Indeed, when I ran into a smaller version of I. orang in Cuc Phuong, with a different thorax pattern, I first thought it would be a different species from the I. orang I know from Ba Vi and Tam Dao. For the time being, let's go with Asahina's interpretation.
This is a spectacular species of forested streams, where males occupy territories on large wet rocks and boulders. Below some photos of both forms.
|Indocnemis orang, male from Cuc Phuong. Note reduced thoracic stripes.|
|Indocnemis orang, f. kempi, from Tam Dao|
|I. orang, f. kempi from Tam Dao|
|And another male from Tam Dao|
|Female I. orang, f. kempi (presumably) from Tam Dao|