Hawaii’s remote location has fostered a unique biological environment, including a diverse population of spiders. The islands’ spider fauna is a mixture of native species, which have evolved in isolation, and a significant number of introduced species that arrived via human activity and trade over centuries. More than 200 species of spiders inhabit the islands, with roughly half of those found nowhere else in the world. This mix of endemic and non-native spiders creates an array of arachnids for residents and visitors to encounter.
Most Frequently Encountered Spiders
The spiders most commonly seen in residential and garden areas of Hawaii are non-native species that have successfully adapted to the tropical climate. The Cane Spider (Heteropoda venatoria), also known as the Huntsman Spider, is perhaps the most infamous due to its imposing size and speed. This large, flat-bodied arachnid can reach a leg span of four to six inches, making it a startling sight. Cane Spiders are nocturnal hunters that do not build webs, instead relying on their agility to prey on insects and cockroaches, making them a form of pest control.
Another common sight is the Hawaiian Garden Spider (Argiope appensa), a type of orb-weaver that constructs large, intricate, circular webs. The female is easily identified by her large size, often measuring two to two and a half inches including legs, and a black and yellow or silvery patterned abdomen. These webs are frequently strung between shrubs or house eaves in gardens and urban settings.
Smaller, but common, are various species of jumping spiders, such as the Bold Jumping Spider (Phidippus audax). They are identifiable by their large eyes and their habit of actively stalking and leaping onto prey rather than using a web.
Medically Significant Species
While most spiders in Hawaii are harmless, a few introduced species possess venom that can cause reactions requiring medical attention. The two main species of concern are the Black Widow and the Brown Widow, both belonging to the genus Latrodectus. The Southern Black Widow (Latrodectus mactans) is glossy black with the classic red hourglass marking on the underside of its abdomen. Its neurotoxic venom can cause severe muscle cramps, pain, and nausea, and any bite should be treated by a medical professional.
The Brown Widow (Latrodectus geometricus) is increasingly common and is typically a mottled brown or gray color, with a distinct orange or yellowish hourglass marking on its underside. Although its venom is potent, the Brown Widow generally injects less venom than its black counterpart and is less aggressive. Both widow species build messy, irregular cobwebs and prefer secluded, dark areas like woodpiles, under outdoor furniture, or in storage sheds. Bites are uncommon, usually occurring when a person accidentally disturbs the spider in its hiding place.
Spiders Unique to the Hawaiian Islands
Hawaii’s isolation has driven remarkable evolutionary diversification, giving rise to unique endemic spider species found nowhere else in the world. The most famous of these is the Happy Face Spider (Theridion grallator), a tiny arachnid measuring less than a quarter-inch long. This spider is named for the distinctive pattern of red, yellow, and black markings on its translucent abdomen, which often resembles a smiley face. These patterns vary widely, even between islands, and may serve to confuse visual predators.
Another group demonstrating this unique evolution is the Tetragnatha genus, or long-jawed spiders, which has diversified into over 50 species in Hawaii. While many Tetragnatha species worldwide build webs, some Hawaiian lineages have abandoned this trait to become active, fast-moving hunters, a shift known as an adaptive radiation. The islands also host highly specialized creatures like the Kauaʻi Cave Wolf Spider, an endangered species that has lost its eyes and pigmentation, adapting entirely to a life in the dark lava tubes of Kauaʻi.