Ass-blasters, like Shriekers, are bipedal with three-toed feet, ending in black talons. They also have long mandibles and jaws, though they lack the distinctive tongue, and use infrared vision to locate prey (though their field of vision seems to be wider and more detailed). However, they have red/pink sail like structures on their backs and tail, and a dorsal sail extending down from neck to tail. These enable the creature to fly after launching itself up. Like all stages in Graboid development, they have a distinctive scent and orange blood.
The chemicals must be mixed near the colon, and seem to be the stomach acid of the creature mixed with another secretion. The combustion is rapid and powerful, explosive and high-temperature (as seen when one attempted to melt through a metal bulkhead). Burt describes the chemicals as 'almost like pure sodium', which reacts strongly with water (Perhaps the chemicals are isolated in an oily substance to prevent an internal explosion).For unknown reasons, they fall into a coma after excessive food consumption, unlike the shriekers which reproduce; this may or may not hint at a fourth form that has never been knowingly witnessed by mankind.
The creatures hunt by flying over the landscape, scanning the ground for heat sources.
They learn at a prodigous rate, identifying the danger posed by Burt's flaming spikes (launched from an improvised potato gun). An ass-blaster who had witnessed the destruction of its fellows learnt to dodge the projectiles.
After a shrieker has lived for about 24 hours, it moults to become an ass-blaster.
Ass-blasters carry a graboid egg, which will hatch into a Dirt Dragon. This is speculated during the third film to enable wide dispersal of the eggs.