Ants

The Ants along with the Queen Ant were part of the viral weapons development led by Alexia Ashford, they were used to experiment with the t-Veronica Virus. The effects of the virus increased their growth which resulted in their abnormal size, and it made them hostile to whatever comes their way. Due to being locked for 15 years, they built a giant ant hill in the room at the bottom floor of the Antarctic Base, and grew in number as countless of them were found crawling around by Chris Redfield.