Do Praying Mantises Eat Spiders? A Predator’s Diet

Praying mantises readily eat spiders, and they do so with the same enthusiasm they bring to almost anything else they can grab. Mantises are generalist predators with remarkably broad diets that span insects, arachnids, and even small vertebrates. The relationship between mantises and spiders is not a one-way street, though. Depending on relative size, the encounter can go either way, and the details of how mantises detect, strike, and subdue spiders reveal a predator far more sophisticated than most people realize.

Spiders Are Regular Prey

Mantises do not specialize. They are opportunistic ambush predators that will strike at nearly anything of appropriate size that moves within reach. Spiders fit comfortably into that category. In controlled predation experiments, mantises captured spiders just as frequently as they captured other arthropod prey, even when those spiders had warning coloration that mimicked chemically defended insects. In one study testing mantis responses to ladybird spiders (red-and-black arachnids whose appearance resembles toxic beetles), roughly 86% of tested mantises attacked all prey types offered, and the rate of attack did not differ between spiders and other arthropods.¹ The mantises were apparently unfazed by the spiders’ visual mimicry of toxic species and captured them at similar rates.

This indifference to warning signals is itself noteworthy. Many predators learn to avoid bright red-and-black prey after a bad experience with a foul-tasting insect. Mantises in the same experiments had recent prior experience with chemically defended bugs, yet they attacked the spiders anyway. The only prey type that gave mantises meaningful pause was a true bug species whose chemical defenses were potent enough to act as a deterrent. Spiders that rely on visual mimicry for protection, in other words, get no benefit from it when a mantis is the hunter.¹

How the Strike Works

The praying mantis’s primary weapon is its raptorial forelegs, which snap shut on prey in a motion that can last anywhere from 60 to about 290 milliseconds. That range might sound wide, but it reflects something interesting: mantises adjust their strike speed depending on how fast the prey is moving. When prey approaches slowly, the mantis extends its leg more gradually and may even pause mid-strike, timing the final downward sweep of the tibia to intercept the target at just the right moment.² The success rate of the strike does not change whether it is fast or slow, which means the mantis is not simply lashing out and hoping for the best. It is actively calibrating.

This matters for spider predation because spiders move in varied and sometimes unpredictable ways. A wandering spider crossing a leaf presents a different challenge than a jumping spider that detects the mantis and bolts. Research on the mechanics of juvenile ghost mantises found that while the sweeping phase of the strike is fairly stereotyped, the earlier approach phase and the amount of body lunge the mantis uses show real flexibility, adjusting to the position and behavior of whatever it is trying to catch.³

As mantises grow, their strike force increases disproportionately relative to body weight. The striking force grows faster than body mass across developmental stages, and larger mantises produce higher tibial velocities during the sweeping motion.⁴ An adult mantis hitting a spider is delivering substantially more force than its size alone would suggest. For a spider caught in the open, the odds of surviving once the strike lands are slim.

A Visual System Built for Moving Targets

Mantises find and judge the distance of prey using a form of depth perception, but it works nothing like human stereoscopic vision. While vertebrates compare static images between their two eyes to calculate distance, mantis stereopsis only works on things that are moving. The system detects regions of the visual field where luminance is changing and uses the slight difference in position of those moving regions between the two eyes to estimate distance. A perfectly still target against a matching background is effectively invisible to this system.⁵

This has direct implications for how mantises hunt spiders. A web-sitting spider that remains motionless is much harder for a mantis to detect than one that is actively moving across a surface. The mantis’s depth perception is finely tuned: it responds most strongly to targets at a specific distance and of a specific angular size, and its strike probability drops for targets that are too close, too far, or the wrong size.⁶ Computational modeling of this system suggests that the peak response corresponds to a distance of roughly 2 centimeters, with the probability of striking declining at both closer and farther distances due to how the target’s image shifts across the mantis’s retina.⁷

The practical upshot: spiders that freeze when they sense a predator gain a real advantage against mantises specifically. Those that keep moving are far more likely to be detected and struck.

When Spiders Turn the Tables

The spider-mantis dynamic flips in certain situations, and the most dramatic reversal happens when a mantis blunders into a spider’s web. Researchers studying this scenario found that out of 26 web-building spiders presented with mantises, seven attacked by casting silk over the mantis to immobilize it. Four of those spiders successfully wrapped the mantis’s raptorial forelegs, neutralizing the one weapon that makes a mantis dangerous. Once the forelegs were bound, the spider could bite the mantis’s abdomen and feed. Four mantises were ultimately eaten this way.⁸

Size determined the outcome. The mantises that were killed by spiders all had body lengths under 56 millimeters. Larger mantises, including two species of the genus Tenodera, eventually escaped, with two of the three successful escapees managing to use their mouths to pull silk off their own forelegs before breaking free.⁸ The mantises tried to counterattack with their forelegs during the silk-wrapping process, but the spiders evaded every attempt with fast lateral movements. No spider was injured by a mantis during these encounters.

The web, in other words, functions as a force multiplier for the spider, negating the mantis’s speed and reach advantages. Outside of a web, the same size spider would almost certainly be prey rather than predator. Inside the web, the spider controls the terms of engagement.

How Jumping Spiders React to Mantis-Like Threats

Jumping spiders are a special case in the mantis-spider relationship because they have excellent vision of their own and can detect approaching predators at a distance. When researchers simulated an approaching predator at different speeds and on different surfaces, jumping spiders responded with three distinct strategies: fleeing directly away, waiting and then running alongside the approaching threat, or dashing underneath and past it. Spiders that detected the model predator at a greater distance fled at a greater distance, and those that ran directly away did so at longer range than those that chose to dash underneath.⁹

These escape decisions were influenced by surface texture (rough versus smooth) and approach speed. The flexibility is notable because it suggests jumping spiders do not simply run when they see a large predator. They assess the situation and pick a response. For a mantis relying on ambush, this kind of threat-aware prey is harder to catch than a wandering ground spider or a web-builder. Jumping spiders’ tendency to be alert, mobile, and visually acute makes them a challenging target, though mantises certainly do catch and eat them when the opportunity arises.

Far Beyond Insects and Spiders

Spiders are just one entry on a surprisingly long menu. A global review of mantis feeding records documented predation on small birds, frogs, lizards, salamanders, newts, shrews, mice, snakes, tiny soft-shelled turtles, and even a small bat.¹⁰ These vertebrate captures are not everyday events, but they are far more common than most people assume, especially for larger mantis species. Hummingbirds are the most frequently reported avian victims, typically caught at feeders where they hover within striking range.

The review also raised an ecological concern worth noting. Non-native mantis species introduced for pest control engage in what ecologists call intraguild predation: they eat other predators, including native mantis species and spiders, rather than focusing exclusively on pest insects.¹⁰ By killing spiders and other beneficial predators, introduced mantises may actually increase pest populations in some settings rather than reduce them. The popular practice of releasing mantis egg cases in home gardens to control pests carries this underappreciated downside.

Do Mantises Actually Help Control Pests?

The ecological role of mantises as pest controllers is murkier than garden-supply marketing suggests. A meta-analysis examining the community-level effects of three mantis species found that mantises generally had weak negative effects on the density of most arthropod groups. The Chinese mantis (Tenodera sinensis) showed more predictable impacts, tending to reduce populations of sap-sucking insects, flies, and plant bugs. The European mantis (Mantis religiosa), by contrast, produced highly variable results that were strongly influenced by whether the experiments were conducted in cages or open fields. Caging actually reversed the direction of the effect for some prey groups, meaning that confined experiments may overstate or misrepresent how these mantises affect wild communities.¹¹

The problem is straightforward: mantises do not discriminate. They eat beneficial insects and spiders alongside pest species. A mantis positioned near a garden aphid infestation is just as likely to grab a visiting parasitoid wasp or a web-building spider that is already eating aphids. This makes them unreliable as targeted biocontrol agents, despite their reputation. They are fascinating generalist predators, but “fascinating generalist predator” and “effective pest controller” are different things.

A Very Old Predator-Prey Relationship

The entanglement between mantis-like predators and spiders appears to stretch back deep into evolutionary time. A fossil preserved in Burmese amber, roughly 100 million years old, captured a larval mantis lacewing (a different insect order from true mantises, but one that convergently evolved raptorial forelegs) in the act of mounting a spider’s leg. The larva’s claws are visibly gripping the spider, frozen mid-interaction.¹² Mantis lacewing larvae are parasites of spiders, not predators in the mantis sense, but the fossil demonstrates that arthropods with grasping forelegs have been exploiting spiders since the Cretaceous period.

True praying mantises evolved their raptorial limbs independently, yet they ended up occupying a similar ecological niche: an ambush predator that regularly encounters and subdues spiders. Whether the prey is a wandering wolf spider, a jumping spider caught off guard, or a web-builder encountered in the wrong place, the mantis’s combination of binocular depth perception, a calibrated high-speed strike, and forelegs lined with spines makes it one of the more effective arthropod predators of spiders in terrestrial ecosystems. Spiders, for their part, have their own formidable weapons. Silk, venom, speed, and keen eyesight give certain spider species the ability to fight back, flee, or even reverse the predator-prey relationship entirely when conditions favor them.