It came from the desert
In San Francisco, talk to Dr. Wong Yi Tze, the Shi's doctor (in the right area). Ask him if he has a job for you, and he will tell you about the problem of the ants near San Francisco that could soon become a problem. You will have to go to the nearest ants nest and kill all the insects there. Dr. Wong marks the location on your map (it's approximately four squares north-east of San Francisco).
Though the ants may seem like a week opponent, this quest is more difficult than it looks like. In the ants' nest there is around 40 ants, lots of them rushing at you right after you enter the location. Low level characters will most likely die there very fast, and even more experienced characters may have a problem. After you kill all ants, go back to Dr. Wong to get your reward.
You can do this quest multiple times, if you wait enough (75 real minutes between two sessions of this quest).
Note: This quest uses ad-hoc created locations. Do not use them as storage facility, because they will be automatically removed by server after some time.