Crocodile: Argog (Sounds blunt and tough)
Mantis: N'elaveah, or Ve for short. (Foreign name structure that fits for a "foreign" species)
Lizard: Agama (literally a just a common name for orange lizards)
Tarantula: Octane (Oct = 8. 8 and 2 could be very symbolic in the Tarantula nation as eight symbolizes their limbs and two as the most important even multiple)