They had voracious appetites and were capable of eating nearly everything they wanted to. They could excrete gelatinous fluid from their tails, which they could use to stick people onto walls and ceilings, as they did with the Metatraxi. They reproduced by spores which were identical to grain.
The planet evolved the Metatraxi in order to fight the Grub back, eventually making them leave the planet. They ate even more after this as a way of putting off memories of the traumatic event.
A hatching of Grubs were hidden abroad a shipment of grain being delivered to the planet by the organisation Earth Aid. The shipment was eventually offloaded and the Grub were back on their own planet. Although there was initial hostility from the Metatraxi, the planet had forgave the Grub for their earlier behaviour and ordered the Metatraxi and the Grub to live in peace together.[source needed]