I am going to be honest, i hate the way the rachni look, to me its a poor combination of every cliche movie alien that has ever exsisted
(initiate sarcasm mode) dont the rachni just feel so original (deactivating sarcasm mode)
but i find myself asking why? did they choose this look for the rae intentionally, did they want us to think ofthe rachni in a similiar way that we think of the brood.
YES beyond a shadow of a doubt we are suppposed to think of hte rachni as monsters, they look like monsters they move like monsters. They have an unsettling number of eyes (some of them) like monsters.
They have a unique trait, and that is walking on four legs with the two tentacles (unexplalinable by most natural laws) ththis leaves them looking like bug centaurs. Which is kind of creepy in its own way
so everything about them, even their coloring says "look at me I am a monster"
and those little front arms, crossed in a james bond villian sort of way, one hand barely on top of the other, like he thinks he is some sort of mastermind (he isnt)
why did they do this you ask, because they wanted it to be a big surprise that the rachni were thinking sapient beings hwo havea right to life just like you.
Problem is we alreay knew this, we knew this at the exact moment we were informed that at some point in the past the rachni were capable of superluminal travel.
in short, i think somewhat that bioware was afraid to go with a more original design,afraid that people wouldnt know what to think of a more original alien
they wnet with a monster that they knew we would identify as a monster
(note brood from marvel comics also have improbable tentacles, who decided that bugs have tentacles?)