- "Sawed-off penis with teeth's heading for Central Park, leaving a wet red trail!"
- – Darkling to Jackie and Sara. [src]
Chestbursters resemble large worms, beige or brown in color and with a mouth of metallic teeth and a tail capable of propelling the creature at considerable speed. Some Chestbursters have been seen to possess arms, but this is not always the case, with others merely having small stubs where presumably the arms will eventually develop. It is possible a longer gestation period may determine the presence of arms at birth; notably, Queen Chestbursters (which have a considerably longer gestation period) have been known to birth with all four of their arms present, as well as legs and a partially developed head crest.
Even regular Chestbursters have been known to birth fully formed, with arms and legs, essentially just a smaller version of the adult that it subsequently develops into. The reason for this is unclear, although it has been theorized that, in cases where a Chestburster is unable to escape its host's body at the usual time (perhaps due to greater structural integrity of the host's ribcage and chest cavity), the host may die prematurely as a result of the invasive organism within them, which will subsequently develop further until it is large and strong enough to emerge.
During development, the Chestburster is attached to the host via a small umbilical cord, through which it presumably gathers the nutrients it needs to grow. Owing to the Xenomorph's tendency to assimilate a degree of its host's genetic traits via the DNA Reflex, Chestbursters will also vary widely depending on the lifeform in which they gestate. For example, Xenomorphs born from Yautja will feature the mandibles of their host at birth.
A chestburster violently erupted from Pellegrini's chest. After checking its surroundings, it escaped to Central Park.