[6] P. rajaei was officially described in a 2012 publication of the British Tarantula Society.

[3] It was discovered in 2009 when a villager brought a dead specimen to Ranil Nanayakkara, the co-founder of the Sri Lankan Biodiversity Education and Research organization, who was conducting an arachnid survey of Sri Lanka at the time.

The venom of P. rajaei is not lethal to humans but can kill small rodents, birds, lizards and snakes.

It is not yet known exactly how rare the newly discovered tarantula is, but there is some concern that habitat destruction is causing their number to dwindle.

The species was named for Michael Rajakumar Purajah, the local police inspector who guided the research team while they searched for living specimens.