Understanding Evolution

Research Profiles : Aloha, spider style! :

The happy-face spiders

Hawaii map showing occurrence of happy-face spiders
The happy-face spider exhibits an array of color patterns on the back of its abdomen, sometimes resembles a smiling face. These spiders blend in with the undersides of leaves where they build their flimsy webs and catch prey.

The happy-face spider is endemic to the Hawaiian archipelago but is only found on four of the islands: Oahu, Molokai, Maui, and Hawaii. The spider populations on these four islands show off a variety of happy-face patterns. Such a variation in form is referred to as a polymorphism — many forms (also known as morphs).

Some varieties of happy-face patterns
Some of the varieties of happy-face patterns. A plain yellow morph is second from the left.

The most common color morph, plain yellow, has no smile. However, the yellow morph is not alone in the forests, and spiders with different color patterns in many forms of smiles (and frowns) can be found with little effort. These different morphs are caused by the different gene versions carried by the spiders.


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Photos of happy-face spiders courtesy of Rosemary Gillespie, University of California Berkeley.

Understanding Evolution © 2019 by The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California