“She's into close relationships, shake to escape!”
—Game description (Spyro's Adventure)
“Shake to avoid a sticky situation”
—Game description (Giants)
Gargantulas are huge spiders that are commonly found in The Underworld, such as the Crawling Catacombs. These massive spiders shoot a strand of sticky web at Skylanders that get too close. The Gargantulas pull in their prey and strike for a lot of damage unless the Skylander can break free. When defeated, they will produce a small number of Spider Swarmers or Spiderlings, depending on the game. However, they do not produce Spiders in most Heroic Challenges.
In the strategy guide for Giants, they are the only enemies with all their stats shown as EXTREME.
Unlike other Spiders who have only four legs, Gargantula has six.
Because they spawn smaller spiders when defeated, much like real life female spiders carrying their offspring on their backs, one can assume they're all female.