here's a weird one: Is it true that when a fly lands on something it vomits ?

Flys vomit enzymes on food scources, the enzymes then dissolve the food and the fly can suck it up.

No. The fly spits digestive juices on things it intends to eat, but if it simply lands on something, it doesn't vomit on it. Flies do have bacteria on them though, and can spread bacteria by landing on things.

A fly's mouth parts can only regurgitate and aspirate liquids. If it lands on a particulary nice goodie it can only slurp up liquids or dissolve the stuff with, as you so delicately state, its own vomit.

Yes it does. It's nasty, but watch the last half hour of the movie "The Fly", and you'll see what's left of Jeff Goldblum doing it.... and if you watch the whole movie, he explains it, too. Yuck!

Yes it does.

yeah. its pretty gross. :P