Snakes can accurately capture prey in the night. In addition to the function of collecting odor, many kinds of snakes also have a device to feel the change of heat energy, which is a heat sensor, which is called buccal fossa or "hot eye".
This "hot eye", located between two eyes and nostrils, is generally 5mm deep and only as long as a grain of rice. It can sensitively measure the change of external temperature. Even if there is only 1 / 3600 ℃ difference, it can feel it. The "hot eye" is in the shape of a horn, with the bell mouth inclined forward, which is divided into internal and external parts by a film. The inner part has a thin tube leading to the front corner and connects with the outside with the help of a small hole, so the temperature inside is the same as that of the surrounding environment where the snake is located. The outer part is a heat collector. If there is a hot object in the direction opposite to the bell mouth, the infrared ray will irradiate the outer side of the film through here. Obviously, this is higher than the temperature on the inner side of the film. The biological current generated by the temperature difference formed on both sides of the film is transmitted to the snake's brain through nerves. When the snake knows where there is a hot object in front of it, the brain sends out the corresponding "command" to capture the object.
Rats are a kind of rodents that like to haunt at night, and Agkistrodon halys also likes to hide and hunt in the dark. Although the mouse is cunning enough, its heat cannot escape the "hot eye" of Agkistrodon halys, and it will be caught by agkistrodon halys.