Spiders occupy a fascinating and often misunderstood niche in the global ecosystem. As some of the most efficient predators on Earth, their dietary habits are far more complex than the common image of a house spider catching a stray fly. Across the thousands of known species, the question of what spiders eat reveals a world of opportunistic hunting, specialized strategies, and even surprising exceptions to their carnivorous reputation.

The insect-heavy foundation of the spider diet

For the vast majority of spiders, insects are the primary source of nutrition. This dietary focus makes spiders one of the most important natural controllers of insect populations. In any given garden or forest, spiders are actively culling the ranks of pests that would otherwise overwhelm the environment.

Common prey includes:

  • Dipterans (Flies and Mosquitoes): These are the staple food for many orb-web weavers. The aerial nature of flies makes them perfect targets for vertical sticky webs.
  • Orthopterans (Crickets and Grasshoppers): Larger ground-dwelling spiders, such as wolf spiders, frequently target these high-protein insects.
  • Hymenopterans (Bees and Wasps): While dangerous due to their stings, many spiders have evolved specific wrapping techniques to neutralize these insects before they can strike back.
  • Lepidopterans (Moths and Butterflies): These are often caught by nocturnal hunters. Interestingly, some moths have evolved scales that shed to allow them to slip out of webs, leading to an evolutionary arms race where some spiders create "ladder webs" to catch them as they tumble downward.

As of April 2026, with spring in full swing in the Northern Hemisphere, the emergence of early-season gnats and beetles provides a crucial energy boost for spiders coming out of winter dormancy. This seasonal abundance dictates the growth patterns and reproductive success of most local spider populations.

Big game hunters: Spiders that eat vertebrates

While we typically associate spiders with tiny prey, several larger species are capable of overpowering and consuming vertebrates. This occurs when a spider’s size and venom potency allow it to take down animals much larger than itself.

Fishing spiders (genus Dolomedes) are a prime example. These semi-aquatic hunters rest their legs on the surface of the water, sensing vibrations from movement below. They are known to dive and capture small fish, minnows, and tadpoles. Their venom is specialized to quickly paralyze aquatic prey, which might otherwise escape into the depths.

In tropical regions, the scope of the spider diet expands significantly. The Goliath birdeater (Theraphosa blondi), despite its name, rarely eats birds, but it frequently consumes rodents, frogs, and lizards. There are documented cases of large orb-weavers capturing small bats or even songbirds that accidentally fly into their massive, incredibly strong silk structures. However, these are typically opportunistic events rather than a primary food source.

The liquid diet: How spiders actually consume food

One of the most distinctive aspects of spider biology is their inability to consume solid food. Unlike humans or other mammals, spiders have a very narrow gut that can only process liquids. This necessitates a process known as extra-oral digestion.

When a spider catches its prey, it first immobilizes it using venom delivered through its fangs (chelicerae). Once the prey is still, the spider begins the digestion process outside its body. It regurgitates powerful digestive enzymes into or onto the prey's body. These enzymes break down the internal tissues of the insect, turning its muscles and organs into a nutrient-rich "soup."

The spider then uses its pumping stomach—a muscular organ located in the cephalothorax—to suck up the liquefied remains. What remains at the end of the meal is often just a hollowed-out exoskeleton, which the spider discards. This method of feeding is highly efficient, allowing the spider to extract maximum nutrition while leaving behind indigestible chitin.

Spider eat spider: Cannibalism and theft

Spiders are not particularly social creatures, and many species view their own kind as just another potential meal. Cannibalism is a widespread phenomenon in the arachnid world, occurring in several contexts.

Sexual Cannibalism is perhaps the most famous. In species like the Australian redback or certain black widows, the female may consume the male before, during, or after mating. While this seems brutal, it often serves an evolutionary purpose, providing the female with the necessary nutrients to produce a large number of healthy eggs. The male, in some cases, even facilitates this process to ensure his genes are passed on.

Non-reproductive Cannibalism occurs when resources are scarce. If insects are hard to find, spiders will readily hunt other spiders. Some species have specialized in this. The pirate spider (family Mimetidae) does not build its own web to catch insects. Instead, it enters the webs of other spiders and mimics the vibrations of a trapped insect or a potential mate. When the resident spider approaches to investigate, the pirate spider strikes with a paralyzing bite.

There are also kleptoparasitic spiders, such as those in the genus Argyrodes. These tiny spiders live on the outskirts of the large webs built by orb-weavers. They survive by sneaking in and stealing small prey items that the larger spider ignores, or even by cutting out and carrying away a silk-wrapped meal while the host is busy.

The vegetarian exception: Bagheera kiplingi

For a long time, it was believed that all spiders were strictly carnivorous. However, researchers discovered a remarkable exception: Bagheera kiplingi, a species of jumping spider found in Central America. This spider lives on acacia trees and derives the majority of its diet from "Beltian bodies"—specialized, nutrient-rich leaf tips produced by the tree.

While Bagheera kiplingi may occasionally supplement its diet with ant larvae or nectar, it is the only known spider to be primarily herbivorous. Other spiders have been observed consuming nectar or pollen, but these are generally considered opportunistic snacks to provide quick sugar or moisture, rather than a primary food source. For most spiders, a diet consisting only of plant matter would lead to malnutrition and death, as their digestive systems are fine-tuned for animal proteins.

Hunting strategy determines the menu

A spider's diet is heavily dictated by its hunting style. This can be categorized into three main groups:

  1. Web-Builders: These spiders (like orb-weavers and cobweb spiders) are passive hunters. Their diet depends entirely on what flies or crawls into their traps. They are often less picky, consuming almost any insect that gets entangled, provided it isn't too large to handle.
  2. Ambush Hunters: Crab spiders and trapdoor spiders wait for prey to come to them. Crab spiders often hide in flowers, camouflaged to match the petals, and wait for pollinating insects like bees or butterflies. Their diet is highly specific to flower-visiting insects.
  3. Active Hunters: Jumping spiders and wolf spiders roam their environment in search of food. Jumping spiders have exceptional vision, allowing them to stalk prey with feline-like precision. Because they can see their prey from a distance, they can be more selective, choosing high-energy targets like flies or even other spiders.

Scavenging and the preference for the dead

While we view spiders as active predators, recent observations suggest that scavenging is more common than previously thought. Some species, like the brown recluse (Loxosceles reclusa), have shown a surprising preference for dead insects over live ones in laboratory settings. This indicates that spiders are opportunistic and will not turn down an easy meal that requires no energy to kill.

This scavenging behavior is likely a survival mechanism for times when live prey is scarce. By consuming dead insects they encounter, spiders can maintain their energy levels during droughts or cold snaps when insect activity is low.

Why their diet matters to us

Understanding what spiders eat is crucial for appreciating their role in our lives. In an average suburban garden, spiders may consume hundreds of pounds of insects over a single season. This includes mosquitoes that carry diseases and agricultural pests that destroy crops.

Without spiders, the global insect population would explode, leading to devastating impacts on food security and human health. By maintaining a diverse diet that spans the entire insect world—and occasionally reaching into the vertebrate world—spiders act as a critical stabilizing force in almost every terrestrial habitat on Earth.

Whether it's a tiny jumping spider sipping nectar or a massive tarantula overpowering a lizard, the diet of these eight-legged predators is a testament to their evolutionary success. They are the ultimate opportunists, capable of turning almost any small living creature into the fuel they need to survive and thrive.