Because boa constrictors, reticulated pythons, and anacondas are some of the biggest snakes in the world, many people get confused about which is which. The first thing to note is that the anaconda is a species of boa, not a separate type of snake. That leaves two groups, the boas and the pythons. These snakes have some things in common: they are constrictors, killing their prey by wrapping around it and suffocating it, and they are considered primitive snakes with two lungs (most snakes have only one) and remnants of hind legs and pelvic bones.