Black widow spiders have a surprisingly long list of natural enemies. Despite their potent venom, they are regularly hunted by certain wasps, spiders, lizards, and birds. Some of these predators have evolved specific strategies to neutralize the black widow’s defenses, while others simply overpower them.
Mud Dauber Wasps: The Most Effective Predator
Mud dauber wasps are the best-documented and most efficient predators of black widow spiders. Female mud daubers hunt black widows by stinging and paralyzing them, then packing the still-living spiders into mud nest cells for their larvae to eat. A single nest cell can contain up to 25 paralyzed spiders, each one kept alive and intact until the wasp larva hatches and consumes them. The blue mud dauber (Chalybion californicum) is particularly well known for targeting black widows specifically.
What makes this predator-prey relationship remarkable is how deliberate it is. The wasp doesn’t stumble across black widows by accident. She actively seeks them out, enters their webs, and delivers a precise sting that immobilizes the spider without killing it. Once the cell is packed with prey and an egg is laid inside, the wasp seals it shut and moves on to build the next one. If you see mud dauber nests around your home, they may actually be reducing the local black widow population.
Cellar Spiders Hunt From a Safe Distance
Cellar spiders, the long-legged, delicate spiders common in basements and garages, are capable of killing black widows. Their technique compensates for their smaller size and lack of potent venom: they cast long strands of silk onto the black widow from a safe distance, wrapping it up before it can bite back. Once the black widow is securely bound, the cellar spider moves in to feed.
This silk-throwing strategy is effective enough that in some regions, cellar spiders are considered beneficial precisely because they prey on more dangerous species. The matchup looks wildly uneven on paper, but the cellar spider’s ability to immobilize from range gives it a real advantage in the tight spaces where both species tend to live.
Lizards and Other Reptiles
Several lizard species eat black widows as part of a varied diet. Alligator lizards in the western United States are probably the best-studied example. A 1937 study by herpetologist Raymond Cowles identified the San Diego alligator lizard as a likely major predator of black widows. Later stomach-content studies found spiders from the black widow family (Theridiidae) in the guts of multiple alligator lizard subspecies, with one subspecies yielding black widow remains in 20 individual lizards examined.
That said, black widows never appeared to be a staple food for any lizard species. They show up as one item among many in a generalist diet, alongside beetles, crickets, and other invertebrates. Lizards that forage in dark, sheltered spaces where black widows build their webs are simply more likely to encounter and eat them.
Birds Are Cautious but Capable
Birds can and do eat black widows, but the spider’s signature red hourglass marking works as a warning signal that deters many would-be attackers. Research from Duke University found that birds were three times less likely to grab a spider model displaying a red hourglass than one without the marking. The color contrast of the hourglass is more than twice as visible to birds as it is to insects, meaning the warning is specifically tuned to scare off predators rather than alert prey.
Smaller, short-beaked birds like house finches and chickadees were the most easily spooked by the warning coloration. Larger or bolder bird species are less deterred and will eat black widows when the opportunity arises. The hourglass doesn’t make the spider untouchable. It just shifts the odds, filtering out smaller birds that would be most vulnerable to the venom.
Tiny Wasps That Destroy Egg Sacs
Not all predators target adult black widows. A tiny parasitic wasp called Baeus latrodecti attacks black widow egg sacs directly. The adult female wasp chews through the silk of the egg sac and lays one egg inside each spider egg. The wasp larvae then consume the developing spiderlings from the inside. Within a single egg sac, parasitism rates can approach 100%, meaning the wasp can wipe out an entire clutch before any spiderlings emerge.
This form of predation doesn’t reduce the adult population directly, but it can have a significant impact on black widow numbers over time by eliminating entire generations before they hatch.
Sexual Cannibalism Among Black Widows
Black widows also eat each other. The species gets its common name from the female’s tendency to cannibalize the male during or after mating. In some widow spider species, this happens regularly, with the male essentially sacrificing himself as part of the reproductive process. Males of the Australian redback spider (a close relative) even perform a “copulatory somersault” that places their body directly over the female’s fangs.
Cannibalism isn’t limited to mating encounters. Immature female black widows have been observed killing and eating adult males in the wild, even before their reproductive organs are fully developed. This means males face the risk of being consumed whether or not mating actually occurs.
How Black Widows Defend Themselves
Black widows aren’t helpless against their predators. Their venom is the most potent of any spider in North America, stronger drop-for-drop than rattlesnake venom. For small predators, a bite can be lethal. Their irregular, sticky webs also serve as a first line of defense, alerting the spider to approaching threats and sometimes entangling attackers.
The red hourglass is a classic example of aposematic coloration, a biological warning sign that advertises danger. It functions the same way bright colors work on poison dart frogs or coral snakes: predators that have learned (or evolved to recognize) the signal tend to avoid the animal entirely. This visual deterrent is effective enough against birds that it likely prevents far more predation attempts than any other defense the spider has. Still, specialized predators like mud dauber wasps and cellar spiders have evolved workarounds that make the venom and warning colors largely irrelevant.