According to an insect expert at the University of Bergen in Norway, if you have a real Christmas tree . . . it's probably CRAWLING with BUGS.

Associate professor Bjarte Jordal said that real trees can be home to up to 25,000 different insects and spiders.

Things you'll find in your tree include springtails . . . which are sometimes called book lice or snow fleas . . . and also spiders, moths, mites, and bark lice.

Most of them burrow into the tree and hibernate for the winter . . . but when you bring the tree inside your nice, warm home, they WAKE UP.

The good news is that most of those bugs live IN the tree . . . which means they're probably not going to leave it and spread throughout your house.  Your house is also dry . . . and there's not a lot of food for them.  So they'll die pretty quickly.