L. a. nigromarginatus is a bright green, slender, medium-sized, snake. Adults are typically 60–100 cm in length. Black edges around the outer margin of each scale form a distinctive net-like pattern on the dorsal surface of the animal. The ventral surface has a metallic sheen, and may be green or rust-colored.
It is arboreal, living in dense brushy vegetation. It is found in secondary and primary forest.
Active during the daytime, sleeps in vegetation at night.
It feeds on lizards, frogs and small birds.