I think this spider has been genetically modified.
Karamja volcano; Varrock sewers; Edgeville dungeon, wilderness area; Rune rocks, level 42 wilderness; Arandar pass, east of Isafdar
Good training for medium level players. Bring along some food, Adamant or better armour and weapon. If they stop becoming aggressive, simply log out for about 2-5 minutes and log back in and they will start becoming aggressive again.
Deadly red spiders are often found guarding their eggs, which are used in Herblore.