CARBONDALE, Colo. -- Warning: This is a graphic story, not for the squeamish.

Video: Flies In Scalp | Slideshow

A Colorado man is recovering after a 5-week ordeal that started when he returned from Belize with botfly larvae growing under his scalp.

Aaron Dallas and his wife had returned home from their trip when he noticed strange bumps on back of his head. After 5 weeks, the bumps got bigger and began to hurt.

Five botfly larvae apparently left by a mosquito were growing in his head.

"The biggest ones were not quite as big as my thumbnail," Dallas said. "There was a different sort of pain ... The pain started out as a minor inconvenience and by the end of it it felt like someone was driving a nail through my head."

Dallas said it got to the point he could even hear a ticking in his head.

"It was like something chewing or nibbling," he said. "I went to a doctor ... He pulled my hair back, and I believe his exact words were, 'Oh, my god,' because he could see them moving."

The doctor quickly removed the five growing botfly eggs.

"Because of the Novocaine it didn't hurt, but I could feel and hear them coming out," Dallas said.

All that's left of the flies are the air holes the larva left in Dallas' head. Although he's recovered fully, he said the idea of it still gets under his skin.

"It still gives me a queasy feeling every once and a while," Dallas said.

Experts say the best defense against this happening is to wear bug spray from head to toe and use a mosquito netting at night.