Patterns on the back of a spider in Hawaii create an image that resembles a human smiley face.

A smiley spider. Photo: National Geographic.

Theridion grallator, also known as the smiley face spider, is only a few millimeters long. They live in tropical forests in the Hawaiian Islands (USA) and are completely harmless to humans. The most unique feature of this spider is that its back has patterns that resemble a smiling human face.

Dr. Geoff Oxford, a spider expert at the University of York (UK), said: “I have to admit that I couldn’t help but laugh when I saw a Theridion grallator for the first time.” Scientists have made many hypotheses about the existence of smiley faces on spiders’ backs, including one hypothesis that this face helps them deceive their enemies.

“When a bird or predator encounters something they have never seen before, it takes them a few seconds to decide whether to attack the target or not. Smiley-faced spiders will take advantage of the enemy’s hesitation to escape,” Oxford explained.

Not all smiley spiders have smiley faces on their backs. Many have only blue or orange backs. Smiley-faced spiders only live in tropical forests in the Hawaiian Islands. They are facing the risk of extinction due to the appearance of many animals from other places.

“The smiley spider is representative of all the species that are about to become extinct in the Hawaiian Islands. Their images are printed on T-shirts, baseball caps, postcards and even trucks. Hawaii’s fauna and flora are threatened by species that humans bring from elsewhere. Today most of the animals and plants in Hawaii originate from elsewhere and we have to go into the rainforest if we want to find native species,” Oxford said.