It's the stuff nightmares and horror movies are made of.

A holidaymaker got a nasty shock when he learned that the strange bleeding bumps on his head were not bites or shingles, but live maggots.

Aaron Dallas, from Colorado, looked for medical help when the unusual lumps appeared on his scalp after a holiday to Belize during the summer.

One doctor thought they might have been caused by a gnat bite. Another believed his problem was shingles.

But then the bumps took on a life of their own and began to move.

A doctor discovered five bot fly larvae living inside Aaron Dallas's head, near the top of his skull. This was a few weeks after a mosquito had apparently placed them there.

"I'd put my hand back there and feel them moving. I thought it was blood coursing through my head. I could hear them. I actually thought I was going crazy," said Dallas, of Carbondale.

Bot flies rely on mosquitoes, stable flies, and other insects to carry their eggs to a host - and in this case the host was Dallas.

"It was weird and traumatic," he said. "I would get this pain that would drop me to my knees."

After their discovery the parasites were removed by a doctor. Dallas's wife teased him about it afterwards, but didn't find the experience funny.

"It's much funnier to everyone else. It makes my stomach turn over. It was cruel,'' he said.

Bot fly infections are fairly routine in parts of Central and South America.

- July , 2007