The most common type of Americanus, A. fatassus, mostly inhabits cities like Houston and Chicago.
It is often seen gathered around fast-food joints, and is easily recognizable because it is the most massive of all the species.
A. fatassus is a parasitic omnivore, and it uses its lobes of fat to suck the ambient life force out of the surrounding environment.
The obese Americanus will also eat anything, be it shit-grade beef or compressed garbage, so long as it is sandwiched in a burger bun or taco shell.
It eats in large volumes, and stores the fat in the huge body sacs that give it its typical appearance.
Americanus saves fat to convert to stored energy in case it has to do something strenuous, like walking ten feet.
Its two-ton body is, in many cases, too heavy to move without aid, and so it relies on giant people-movers and Chelsea tractors to cart itself around (much like Jabba the Hutt on his sail barge).
Males and females are indistinguishable, because overhanging rolls of fat block the genitals from view, which in the male are insignificant anyway.
Further confusing gender identification are the man-boobs seen on chest of the male.
One should avoid mating with them, or watching them mate, at all costs.
Warning: Americansus, like plastic bags, must not be left near children unsupervised. Children may be stepped on, sat on, or become hopelessly entangled in rolls of fat. Infants especially must be kept away, as direct contact with the fat lobes will instantly snuff the life force out of them.
I'm well aware of the work of Flemming on anti-biotics and sulfa drugs. Two staggering acheivements of medical science.