It is the first film of the Species franchise that does not feature Natasha Henstridge, who played Sil in the first film as well as Eve in the two previous movies (even though her role in La mutante 3 (2004) was a small cameo).
While the previous films heavily used animatronic puppets, the alien creatures are fully portrayed by actual stand-ins in this installment. A male alien design was also created, although the creature is barely seen in the final film.
The producers wanted to go back to H.R. Giger's designs of the alien creature due to popularity with fans and the absence of this decision in La mutante 3 (2004). The original look is apparent but with different color variations and new spikes on the aliens' wrists of the nemesis.