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For arachnophiles and arachnophobes alike, the black widow spider (genus Latrodectus) is often the benchmark of fear. Although these venomous arachnids can deliver a painful bite—rarely lethal—they are surprisingly widespread, inhabiting every continent except Antarctica and every country across North and South America. In the United States, they appear in all 50 states except one.
The state that remains free of black widows is Alaska. The explanation is simple: the climate. Most scientists believe that Latrodectus species originated in equatorial zones, and their physiology reflects that preference for warm environments. A 2023 study measured the thermal tolerances of three U.S. black widow species and found that only the western black widow can survive subfreezing temperatures, and only down to roughly 30 °F.
Researchers identified the average low temperature of the coldest month as a reliable predictor of species distribution. For instance, Juneau—one of Alaska’s southernmost cities—has an average low of about 25 °F in its coldest month, below the western black widow’s survival threshold, rendering the state inhospitable for the species.
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If you’re planning a move to Alaska, you’ll find a diverse array of spiders that have evolved to thrive in the state’s harsh winters. The most noticeable among them are fishing spiders and wolf spiders, each capable of exceeding three inches in length. While sizable, their bites are not medically significant, unlike the black widows and brown recluses that pose a risk elsewhere in the country.
Some spiders simply cannot withstand the sub‑zero temperatures. Many female spiders deposit their egg sacs in sheltered spots to protect them through the winter, often at the cost of the mother’s survival. Others enter a state of diapause—a temporary suspension of development—to survive the cold months, and some combine these strategies, with newly hatched spiders pausing their growth while still within the egg sac.
At least three species of Alaskan spiders have evolved a biochemical adaptation that functions as natural antifreeze. These antifreeze proteins in their hemolymph lower the freezing point of their internal fluids and restrict ice crystal growth, preventing cellular damage during prolonged cold periods. While Alaska may lack black widows, it does host some of the world’s most resilient arachnids.
