In a mountainous area of Brazil, there is a kind of beautiful butterfly which can kill men. If people meet them, they will come down in great quantities to bite and kill, sucking blood and flesh through the wounds they cause. In June, 1966, a boy named Marl Andre who went into the mountains in search of butterfly specimens   was killed by these butterflies. A country boy saw him when he was just about to catch a butterfly. Suddenly thousands of butterflies came down upon him, covering him all over. The boy struggled and cried as he tried to free himself from their attack. Finally he fell senseless to the ground. Police examined his body and proved that he had died of bites by butterflies. In New Guinea, there is a kind of needlefish which also kills men. Needlefish likes light. At night, it will swim near the lights of fishing boats, then suddenly shoot out of water like an arrow to its target, and force its 3-inch sharp mouth into a human body. Of-ten people are thrust in the eye, or through the chest or stomach, resulting in death. Sometimes it will even attack the people in a fishing boat in broad daylight. About 10 persons in the world are killed by sharks every year, yet more than 240 people are killed by needlefish every year. From the passage, we know that   _  .
butterflies are living in the mountains all butterflies like sucking blood and eating fish the butterflies in a certain part of Brazil can kill men the more beautiful a butterfly is, the more dangerous it is