The Black Mourning Spider is according to the Professor the deadliest spider in the world because of its venom. It appears to be almost five feet long and around 500 pounds with legs attached to a large bulbous body rather than a middle thorax like its regular-sized relatives. Because of its large eyes, it might be particularly sensitive to light, living in caves and openings large enough to support it before going out at night to search for food. However, to support its diet, it would have eat three times its size in order to exist, likely catching and consuming small animals. Gilligan unknowingly places Walter the Pigeon in the spider's cave, making it difficult to retrieve Walter later. The Professor gets the spider addicted to berry juice before getting himself, the Skipper and Mr. Howell trapped in the cave behind it. Mrs. Howell and the girls try rescuing them by distracting the spider with a reflection of itself, but Gilligan breaks the mirror and gets them all trapped. However, Walter attacks the spider and causes it to flee into the jungle. Its whereabouts if it is still alive are unknown.
- The Black Mourning Spider was played by actor Janos Prohaska.
- Realistically speaking, a spider of extraordinary size would have to subsist on all the small animals it could catch and drag back to it its cave to eat at its leisure; the Castaways should have discovered it in the early few months of their existence on the island.
- According to GilligansIsle.com, the Black Morning Spider is originally from the island of Scartiel. When it is born, it resembles a small tarantula, but it can grow to be over 750 pounds. The tiny isle got so infested with these gargantuan spiders that no human or mammal could live there. In 1945, the U.S. Army dropped a bomb on the island and killed every last one except the one that apparently still lives on Gilligan's Island, making it 63 years old.
- The spider also appeared in the first season episode "The Keeper, Part 2" of Forbidden World, and as a judge to Dr. Smith in the "Prisoners of Space" episode of Lost In Space.