Drone

A drone is spawn of the mother grub, laid asexually between broods.

Biology
Drones are hard-carapaced, and characterised both before and after pupation by the chitinous barbs that grow from their cranial and torsal plates.

During their larval stage, drones are prone to violence and cannibalism between broodmates - perhaps even moreso than in trolls - leading to a pseudo-social system in which drones with higher weight, having been able to consume more of their brethren, garner more respect from their peers. Upon entering their pupal stage, drones with a weight higher than a usual threshold of 60 kilograms will undergo a separate transformation to lighter drone larva, emerging from their metamorphosis as a special morph known as rex.

Role in the Empire
Drones are collected in the brooding caverns en masse during their pupal stage to be put through biomechanical alteration in order to optimise their performance in the role of Imperial Drone.