After heading to Gulf of Gunthak and swamp of no hope with few mobs to be had I went to mountains of rathe and there were tons of mobs on track. I would highly suggest heading there for these. They spawn on and around a hill near location 388, 1662, 135. The respawn rate is every couple of minutes so you should be able to farm what you need fairly fast here.
Also note if you are not getting any respawns or if none are up at this location just kill everything that moves. If you selectively kill just the mosquitos I found they slowly stop spawning but clearing everything kept them spawning almost instantly.
In Gunthark or some such. Place with a ship you zone into. You swim south thru water then hit beach. Found two giant mosquitos there and one of them had this. Povar server, March 2006.