Film made in 1979, Directed by Ridley Scott. This takes place in the year 2037 onboard the vessel Nostromo. The crew is made up of Ripley, Dallas, Brett, Parker, Lambert, Kane, and Ash. The vessel recieves a message from an unidentified craft that was in distress on LV-426. The Crew answers the call, but while on the planet, Kane finds thousands of eggs, and one hatches and a creature attachs to his face. Later on the creature falls off, but implants an embryo which births an alien. The alien bursts through his chest, running off into the ship. Later on the Alien picks off the crew one by one until only Ripley is left. She then destroys the ship, and defeats the alien.
An excellent science fiction movie series. Features a race of insect-like aliens called Xenomorphs, which have acidic blood and a collective mentality. They lay eggs like normal insects, but the larvae can only mature into adults by leaping onto a host organism's face and injecting themselves dow into the digestive tract. The adults burrow themselves out of the host, killing it in the process.
Basically, if you have an alien Xenomorph on your planet, your species is doomed.
Not even the Marines were tough enough to face the Xenomorphs in the Aliens movie.