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Theridion grallator, The Hawaiian Happy Faced Spider

The Happy-Faced Spider is a charismatic arachnid endemic to the Hawaiian Islands. T. grallator belongs to the comb-footed spiders (Theridiidae), a family which also includes the famous Black Widow. Happy-Faced Spiders are highly derived members of this group but do not share the venom toxicity of their more feared relatives. These are small spiders, about a quarter of an inch long, who prefer to live on the underside of leaves at elevations from 1,000 to 6,000 feet. Theridion grallator's common name comes from the interesting pattern on its abdomen, which closely resembles a 'smiley face'.

Theridion grallator exhibits behaviors that are extremely rare amongst spiders. One of the more interesting is maternal care. The female Happy Faced Spider will actively care for her young after they hatch from the eggsac. This goes as far as catching prey items for the spiderlings to eat. Less than 1% of all the spiders species on the planet are known to act in this way. Rare behavioral characteristics, like chemical composition or gene resources, contribute greatly to the diversity and survival of life on Earth.

T. grallator also provides an interesting case study in the evolution of species on islands. Scientists have discovered that the genes controlling color pattern in this species are unique to each island. Arguments exist as to whether or not the happy faced coloration provides some sort of adaptive benefit or not. Some believe these spiders only have birds to fear as predators and the patterning assists them in frightening potential diners. Others suggest that the lack of continuity in coloration across the species occurs because of a lack of selective pressure. One can only hope we get a chance to solve this mystery before this and many other unknown species are lost from the Hawaiian Islands.

Currently T. grallator is not covered under any protective program. This is not overly surprising however, as only a few of the many potentially threatened arachnids from the region are benefiting directly from conservation efforts. The greatest risk to the survival of T. grallator is habitat loss. Deforestation of the Hawaiian Islands will absolutely result in the extinction of this species.


R.G. Gillespie; G.S. Oxford. 1998. "Selection on the Color Polymorphism in Hawaiian Happy-Faced Spiders: Evidence from Genetic Structure and Temporal Fluctuations." Evolution. Vol 52, 3, 775-783.

R.G. Gillespie. 1990. "Costs and Benefits of Brood Care in the Hawaiian Happy Face Spider Theridion grallator (Aranea, Theridiidae)." American Midland Naturalist. Vol123, 2, 236-243.

Written by: Eric Denemark, 2008

Original Paper: Byung Joo Nahm, 2006

Image credit: Image Credit