Geonosian Queen

The Geonosian Queen was the head of state in Geonosian society, and the mother of all the geonosians in the hive. The Queen was the only member of their society with six legs rather than just four, and she carried a huge crest on the top of her head. The Queens actual body was similar in size to that of a regular geonosian except for the enormous ovipositor which produced one egg roughly every eight seconds. The Geonosian Queen was immobile due to her outsized ovipositor, and so she spent her whole life in the lower levels of the hive. The only known Geonosian Queen was Karina the Great, who was supposedly killed during the Clone Wars.

Source
-Star Wars: the Clone Wars Season 2: Legacy of Terror