There are many different types of green snakes in the world. They range from harmless to harmful and from small to large. Some are non-aggressive and non-venomous while others are aggressive as well as venomous. It's impossible to include information about all of the world's green snake species in a short article, but it is possible to mention some of the most common ones.
Two common venomous green snakes are the boomslang and mamba. The Dispholidus typus, or boomslang, is a poisonous green snake with a venom that can cause severe bleeding. The boomslang, found only in Asia, is quite aggressive; if disturbed, it will usually strike. Boomslangs live mainly in trees and forested areas and eat lizards as well as other small animals.
Mambas, or Dendraspis angusticeps, are green or black. Mambas are African snakes that are highly feared as they are both venomous and aggressive. As mambas eat mainly birds, they are often found on tree branches. Many green snakes have trees as their main habitat so that they blend in with leaves or bushes. For instance, the Atheris squamiger, or leaf viper, is an African green snake that thrives in forests; although it's venomous, its bite is rarely fatal to human adults.
Australia and Papua New Guinea's non-venomous green tree snake, Dedrelaphis punctulata, ranges from olive to blue-green depending on its habitat. A common snake that eats mostly lizards and frogs, it often captures its prey in tall grasses. If handled, Dedrelaphis puctualata snakes release a foul odor as a defense.
Pythons and boas are green snakes that are often larger than most snake species. One of the world's longest and heaviest snakes is the green anaconda, or Eunectes marinus, which is also known as the water boa. This South American, olive green, black-spotted boa can grow about 18 feet (5 m) long and weigh up to 200 pounds (90 kg). It kills large prey such as jaguars and deer by constricting its body tightly around the animals. The green tree python, Morelia viridis, can be found in Australia's Cape York Peninsula as well as Indonesia and New Guinea; it's often easily identified by the unique way it wraps around tree branches with its head in the center of itself.
Rough and smooth green snakes are common throughout North America. Northern Mexico, Southern Canada and the majority of the United States are home to both of these harmless, non-aggressive species of the Colbridae family. The rough green snake, Opheodrys aestivus, and its smoother-scaled counterpart, Opheodrys vernalis, are small with large eyes. Smooth and rough green snakes are bright-green on the upper body with a yellow or cream underbelly.