Luckily this little guy hasn't found a way through the screen. When mice and birds will eventually peck or gnaw holes in the protective screen the doors are opened for business to the "Cozy Pest Hotel". Once these dirty guests are inside their feces and urine gets soaked into old the fiberglass insulation creating fouls odors and creating the perfect environment for the grown of all sorts of nasty microbes and bacteria. Look up Histoplasmosis to learn one of the many nasty diseases humans can get as a result of vermin intrusion.