Do flies poop or throw up everytime they land?

No, house flies do not vomit or defecate every single time they land. However, if they find food they want to eat, they will secrete saliva and digestive juices onto the food to pre-digest it. House flies cannot eat solid food, so this step is required to absorb something like bread or dried blood. Since flies often feed on feces, it is not uncommon for them to transport fecal matter and disease wherever they go.
Updated on Wednesday, February 01 2012 at 06:41PM EST
Collection: disease