The Asari are confusing..

Their vaginas are like a venus fly trap. Capable of turning itself inside out in order to fertilise one another depending on their preference, interlocking jaws with feelers extending from either side hook into and grab onto the waist area. Effectivy swallowing the now incapacitated hosts genitalia.

Whilst this is happening the 'trap' as we'll call it extcretes a psycotropic ooze that creates a euphoric sensation within the hosts mind.

This allows for the exraction of genetic material through the appropriate orifice.

Absorbing the host DNA allows for genetic diversity in later generations and prevents throwbacks like the Ardat Yakshi.

Which are produced through Asari only intercourse.

*Sips Ryncol*

It's never been confirmed if they have the other lady bits or not... But if they do, I assume it's just used as a birth canal. They bear live young so the baby has to come from somewhere.

Absorbing the host DNA allows for genetic diversity in later generations and prevents throwbacks like the Ardat Yakshi.