Flies in beard

Hi! In a movie" in the shadow of the moon" (documental, about flying to the Moon) there is a song.
Hey Mr. Spaceman
Take me along for a ride
Woke up this morning
I was feeling quite weird
I had flies in my beard
My toothpaste was smeared
Over my window they'd written my name

Flies in my beard - means insects in beard, or is it some sort of expression?

Thank you!