Larvae guns were the living weapons of the Zarbi. They were also mentioned as being Zarbi larvae.
The larvae ejected jets of venom from a pointed orifice located beneath their eyes. A plated shell covered their backs, protecting that area from attack. They were helpless if overturned.
As the larvae guns served the Zarbi, they were in turn subservient to the Animus. They served in the war against the Menoptera. When the Animus was defeated, the Zarbi larvae set about replenishing the planet. (TV: The Web Planet)