Need help with two creatures [Bodysnatcher/Swarm]

[meesophatt]

Hey,

Basically what I am looking for are:

Bodysnatchers:
Very much like the Goa'uld with a little Mind Flayer thrown in for goos measure. They would be very intelligent parasite/symbiotes/ giving the host as well as taking from them.

any thoughts or ideas on what creature would best fit this concept? Or how to make one?

One of my biggest issues is reproduction. I don't like the idea of a queen and was thinking about them being able to reproduce through the hosts. Laying a clutch of 4 - 8 leathery slimy eggs that produce offspring.

I also feel that they should be naturally psionic.

Any thoughts or suggestions?

Swarm:
Basically something like the Tyranids of Warhammer 40K. They destrpy worlds and assimilate or destroy all life they encounter. They are a force of nature. they pretty much function like the Tyranids do. Little more than weapons of mass destruction.

Are there any creatures that can take that role? How might you make a race or type?

Any ideas, thoughts or suggestions would be great.

Thanks.