New Scientist recently ran an interesting article about Greek scientists who say that Cyprian honeybees can kill an attacking hornet by suffocating it: "they will instantly form a lemon-sized ball of about 150-300 bees to engulf any hornet that ventures too close to the entrance," thereby choking off the much larger insect's oxygen. But there's a big hole in the researchers' theory.
The closely related Japanese honeybee swarms hornets in a similar way, killing by a totally different mechanism: the center of its lemon-sized bee ball heats up to 50 degrees Celsius, baking an offending hornet to death. Researchers discovered this in the mid-1990s using thermal imaging equipment. Makes sense. So how did the Greek researchers find out how the Cyprian honeybees finish off hornets? "By a process of elimination," says New Scientist. Uh, does that really count? What if there's some mechanism that the researchers haven't thought about or can't detect?