Very nice.
Very nice... and a little disturbing. In a good way.
The voice for the little crustacean was perfect. Animation was slick (how do you get an insects mouth to actually look like it's talking?) and was relatively funny.
You could perhaps add some 'attempted' speech by the poor human host with the thing in his mouth. I mean his tongue's gone, but sure he can still 'talk'? Also, with the blood draining thing and you colour scheme you could maybe make the blue guy go pale slowly. Or from red to blue. Fits with the whole blood loss thing.
Other than that though, this is one really entertaining flash. Very well animated and thought out with great voice.