The majority of Giant Spiders are common spiders which have been infected through secondary transmission of the t-virus. 1 2 3 4
History
The Giant Spider was first documented in the Umbrella Research Center, having been infected by the t-virus following the attack by the Queen Leech.
During the outbreak of the t-virus in Raccoon City, countless mutated spiders were documented primarily in the city's underground sewer network, having been directly exposed to the virus. It is unknown if their original base form was the same as the Web Spinner B.O.W. used in the Arklay Laboratory experiments. There are virtually no differences between the Web Spinner and the Giant Spider, both physically and in regards to their attributes. This is because the virus shows great stability and adaptability among the subjects.
Attributes
Giant Spiders have the same attack methods as their B.O.W. counterparts, and are no more or less effective than them in combat. Intrestingly however, Giant Spider specimens have retained their ability to spin webs, which was originally lost on the Web Spinner. The majority of Giant Spiders are male, and the few which are female usually harbor dozens if not hundreds of Little Spider specimens in their abdomen. When these females are killed, the Little Spiders will tear out of the remaining body.