The scritters are a pest who have proved difficult to control.
They can be killed by direct contact only, being stamped on for example, and they are immune to noxious gasses
They live off paper and trees.
The scritters were designed to carry incendiary devices in the war zones. They were made in a lab and are part insect part bionic. Unfortunately, there were so many made that they spread over large ground areas and ate all the paper they could find, including whole libraries which were totally destroyed by their savage adventures.
The scritters are bionic insects who are born without a skeleton and need metal parts to function. Hence they nest in landfills where there can be structured by their parents who use powerful teeth and minute saws on their legs to create the shell soon after birth.
After the great warming and the Russian and Chinese wars, there were so many floods and so many scritters that houses were built on high concrete stilts.
Scritters are unable to fly or climb as their metal parts weigh them down.
Because scritters are easy to train, criminal gangs in the zones use them to carry drugs and messages without detection.
Generally, they are a nuisance, They have a short life span and as they age become less reliable as they suffer from some sort of Alzheimer's disease.