Which are the 4 types of aliens a US researcher claimed existed?

Researcher Eric Davis claimed US recovered four alien species from crashed UFOs identified as Grays, Nordics, Insectoids and Reptilians. As per ufologists, Nordics resemble humans and Reptilians are believed to be reptile-like creatures with scaly skin, human-style arms and legs and long tails. Grays are short with large eyes, while Insectoids are humanoid creatures that resemble praying mantises.