|Common Name||Nananana Makakiʻi (Face-patterned Spider)|
|Range||Oʻahu, Molokaʻi, Maui and the island of Hawaii in rainforests at elevations of 300–2,000 m (980–6,600 ft).|
The Happy-face spider, (Theridion grallator), is a spider in the family Theridiidae. Its Hawaiian name is nananana makakiʻi (face-patterned spider). The specific epithet grallator is Latin for "stilt walker", a reference to the species' long, spindly legs.
The spider is up to 5 millimeters (0.20 in) long. Certain morphs have a pattern uncannily resembling a smiley face or a grinning clown face on their yellow body. Each spider has a unique pattern, and the patterns differ from island to island. Some lack markings altogether.
On the island of Maui, the happy types seem to follow simple Mendelian inheritance rules, while on other Hawaiian islands the body inheritance patterns seem to be sex-limited. The variation is possibly a kind of camouflage against birds, their only natural enemies of significance, to counteract pattern recognition by predators. As the pattern may change according to what food the spider has eaten. and as the happy-faced spider is very small, hides during the day, and is thus not a significant prey item for any species of predator, it is more likely that the bizarre variety of patterns serves no significant adaptive purpose at all.
The happy-faced spider lives beneath the leaves of plants, where they also spin their much reduced webs. The females guard their eggs until they hatch, and catch prey for their young. The happy-faced spider hunts mainly during the evening.
The happy-faced spider is endemic to Oʻahu, Molokaʻi, Maui and the island of Hawaii in rainforests at elevations of 300–2,000 m (980–6,600 ft).
The closest relatives of the happy-faced spider are other Hawaiian species, such as theridion posticatum and Theridion kauaiense. This "T. grallator clade" may be more closely related to the genus Exalbidion than to any other species currently classified in the genus Theridion.