I still maintain snakes and spiders (possibly other venomous animals too).
The unnie line will represent the snakes (quite telling because of their lip rings plus the fabrics in their 2nd teaser set are much more flowy compared to Lisa and Rosé's). The maknae line are the spiders (or scorpions), and their costumes are more structured (again, basing on the 2nd teaser sets).
The way the reptile cages get smaller by the age of the member seems to imply that too.