who knows for certain - but Ascaris does like to hang out in the decending colon - so when you do lay on your left and that's when you feel it vibrating etc... it could be an ascaris.. but its just a guess and I've had this experience too.. and it was an Ascaris for me.. hence my guess. From what I've read tape head sits in your stomache and the body in the intestines... I've only felt a tape move once.. and it was a "coiling" slithering feeling rather than a vibration. My experience of of Ascaris is that they vibrate and thrash around when upset - and can tend to feel them quite alot at night if you happen to be laying on one on your left side.