Many members of Gomphidae are not easily spotted and most of them are inhibitants of forests. It was my first time to bump into 
Onychogomphus castor. I spotted a male and a female 
O. castor at the Kijang Waterfall of Kenaboi Forest Reserve. The male 
O. castor has a beautiful curved tail (anal appendages). 
a male Onychogomphus castor
a female Onychogomphus castor