Spiders are predators that play a role in maintaining ecological balance by regulating insect populations. Found globally, they exhibit diverse feeding habits and dietary preferences.
The Staple Diet: Insects and Arthropods
The vast majority of spider species are insectivores, primarily eating insects and other arthropods. Spiders consume a broad spectrum of prey, including flies, mosquitoes, moths, beetles, and grasshoppers. They also frequently prey on other spiders, a phenomenon known as intra-guild predation.
The type of prey a spider consumes often directly relates to its hunting strategy. Web-building spiders, such as orb-weavers, construct intricate silk traps to ensnare flying insects like flies and moths. Conversely, active hunters like wolf spiders and jumping spiders do not rely on webs; instead, they stalk and pounce on ground-dwelling arthropods such as crickets, ants, and various beetles. Ambush predators, like crab spiders, camouflage themselves on flowers or foliage, waiting to snatch unsuspecting insects, including pollinators like bees and butterflies, that come within striking distance.
Surprising Dietary Diversions
While insects form the bulk of a spider’s diet, some species have surprising dietary variations. Larger spiders, including some tarantulas and fishing spiders, have been observed preying on small vertebrates such as lizards, frogs, fish, and even small birds or rodents. This occurs in about 30% of known spider families, particularly in species that are several times larger than their vertebrate prey.
A rare exception is the Bagheera kiplingi jumping spider, which primarily consumes plant material. This species feeds predominantly on Beltian bodies, nutrient-rich nubs found on acacia plants, making it the only known spider with a largely herbivorous diet. Some spiders also supplement their diet with plant fluids like nectar or pollen, which can provide essential carbohydrates and other nutrients.
Cannibalism is another dietary component for some spider species. This behavior can occur due to resource scarcity or as part of reproductive strategies, such as female sexual cannibalism where a female eats the male after mating.
The Unique Way Spiders Eat
Spiders consume prey uniquely, unlike animals that chew and swallow. They do not ingest solid food directly. Instead, spiders employ external digestion, a process where they inject digestive enzymes into their immobilized prey through their fangs.
These enzymes work to liquefy the internal tissues of the prey, turning them into a nutrient-rich “soup.” The spider then uses a powerful, muscular sucking stomach, or pharynx, to draw the liquidized contents into its body. The chelicerae, which are the spider’s mouthparts tipped with fangs, are used to hold the prey and facilitate the injection of venom and digestive fluids. This process leaves behind only the indigestible hard parts, such as the exoskeleton, as a shriveled husk.