My 13 week old choc. Lab has a bright red ring under his belly right next to his hind leg... he is also VERY lathargic which is not like him at all. We just got back from a weekend vacation and we had a sitter stay with him... I know she kept him very active but even so he is usually a ball of energy. What could this be... the vet is closed and the answering service says to only call if it is " an absolute emergency" I looked up ringworm and it says there should be no symptoms except for the fungus itself I am worried

It's a tic bite. You need to take him to the vet and get antibiotics for him. He will perk back up within a day or two after treatment

More than likely it is just a black fly bite. Common this time of year. Do keep an eye on it and note any changes. Chances are his being tired is unrelated to the red ring. He was on vacation, too. Other possibilities are tick bite--ask the sitter if she removed a tick), spider bite, ring worm.