Which viper species uses a tail tip that looks like a spider to attract prey?

The spider-tailed horned viper uses a spider-like tail tip to attract prey, especially insect-eating birds. Its tail ends in a bulb surrounded by elongated, drooping scales that resemble spider legs. The snake waves this unusual structure near its body, creating a convincing imitation of an animal that birds may try to catch.

This is a form of aggressive mimicry, also called predatory mimicry: the predator resembles something attractive to its prey. When a bird approaches the apparent spider, the viper can strike from concealment. Field observations have shown that the tail is moved in a figure-eight pattern and that its movement increases when birds are nearby, supporting the idea that the display is an active hunting behavior.

The species is Pseudocerastes urarachnoides, a venomous viper endemic to western Iran and adjoining parts of Iraq. Its remarkable tail once caused confusion: an unusual specimen collected in 1968 was identified as another viper, and the tail was suspected to be a parasite, deformity, or tumor. The species was formally described in 2006.

Other snakes also use tail-luring, but none has quite the same elaborate spider-like structure.