I know it's been explained more than once, but there's more evidence of the existance of female Turians. On Illium, if you wait around near a bar where there's a bachelor party you can overhear a conversation between a Human, a Salarian and a Turian with an Asari dancing on the table. Through the course of this conversation you learn that the Salarian is about to be married (or whatever the Salarians have instead.. a marriage contract, was it?), organised by the Human (the Salarian doesn't see the point at first, but he comes round later...)
Anyway, the Salarian is eventually convinced of the point of the party, and the conversation goes something like this:
Salarian: Okay, I guess I can see the point now: she [the Asari] is very attractive. But why are Humans an Turians attracted to them?
Human: Are you kidding me? The Asari look just like Humans! Look at their figure!
Turian: What are you talking about? That formation on their heads? They look exactly like Turians.
Human: Wait... you don't think the Asari are mind-controlling us to think they're attractive, do you?
Turian: Oh man. Don't ruin the Asari for me. Do you know how few female Turians there are on Illium?
Sorry that took so long.