First discovered in 1900, little was known about the happy-face spider until 1972. The obviously named happy-face spider is a small spider found in the native rainforests of the islands Maui, The Big Island of Hawaii, Oahu and Molokai at elevations of 1000 to 6000 feet. Typically around a quarter of an inch long, its diet consists of small insects that it hunts mainly during the night for small insects. They spin their webs on the undersides of leaves of specific plants and usually avoid contact with humans or other potentially danger animals, although only birds present a natural threat. Humans present a possible danger due to loss of habitat to agriculture, but the population is apparently healthy. The happy-face spider's most admired feature is its bright yellow coloring and a strange pattern of red and black spots on the abdomen.
These spots vary widely from spider to spider, making them of interest to scientists who have hypothesized that the different spots provide camouflage against birds and other predators. Strangely enough, the red and black spots, combined with the yellow body, tend to make the spider's abdomen look like the widely known yellow smiley face. The expressions on the abdomen of the spider can range from sad, happy, and excited, to bored or angry. Though individuals differ extremely in their color patterns, these differences are evenly distributed, with the same ratio of Yellow forms to Red front forms in every population, regardless of its separation from the others. Mating experiments reveal that the genetic mechanism for achieving these similar color morphs is different on each island. Results for the Maui spiders reveal a more simple system of genetic control where the individual, regardless of sex, will be colored according to a single gene.
On Hawaii, however, it is apparent that two genes determine the color morph, with pairs of color forms restricted to one sex or the other. Since organisms tend to move from the older to the younger islands in hot spot island chains, the genetic differences between the two populations can best be explained as an example of the founder effect, in which a small number of immigrants from Maui would have undergone genetic changes and populated the new island with a new mode of inheriting color variation.