Spiders are fascinating arthropods, known for their predatory nature and diverse adaptations. Their diet primarily consists of other organisms, establishing them as important predators in various ecosystems. This carnivorous diet is fundamental to their survival and plays a role in maintaining ecological balance.
Main Food Sources
Most spiders are insectivores, meaning their diet centers around insects and other small arthropods. Common prey includes flies, mosquitoes, moths, beetles, ants, crickets, and other small invertebrates like worms and snails. Spiders consume hundreds of millions of metric tons of insects annually, highlighting their significant role in natural pest control. Their presence helps regulate insect populations, benefiting agriculture by protecting crops.
How Spiders Catch Their Prey
Spiders employ a range of strategies to capture their food, showcasing remarkable adaptability. Many web-building spiders construct intricate silk structures designed to ensnare prey. These include orb-weavers, which create classic circular webs with sticky spirals to trap flying insects, and funnel-web spiders, which build sheet-like webs with a tubular retreat. Tangle webs, or cobwebs, are irregular, sticky masses of silk that also effectively trap prey.
Other spiders are active hunters, relying on speed and keen senses. Wolf spiders and jumping spiders actively stalk and pounce on prey. Jumping spiders are noted for their excellent vision, which aids in locating and pursuing prey.
Ambush predators, such as crab spiders and trapdoor spiders, lie in wait for prey to come within striking distance. Crab spiders often camouflage themselves on flowers, ambushing pollinating insects. Trapdoor spiders construct burrows with hinged lids, darting out to seize passing prey.
Unusual Diets
While insects form the bulk of a spider’s diet, some species exhibit unusual feeding habits. Cannibalism, where spiders consume other spiders, can occur after mating (e.g., black widows) or during territorial disputes. Larger spiders, including tarantulas and fishing spiders, prey on small vertebrates such as frogs, lizards, birds, and fish. A global survey indicated that species from 39 of 129 spider families can capture vertebrate prey, with some families doing so habitually.
A notable exception to the generally carnivorous spider diet is the Central American jumping spider, Bagheera kiplingi. This species is largely herbivorous, primarily feeding on protein and fat-rich Beltian bodies found on acacia plants. While Bagheera kiplingi occasionally consumes nectar, pollen, or ant larvae, its diet is predominantly plant-based, a rarity among spiders. This adaptation is linked to the year-round availability of Beltian bodies, providing a consistent food source.
Digestion and Water Intake
Spiders do not chew their food in the conventional sense. Instead, they engage in external digestion, injecting digestive enzymes into captured prey. These enzymes liquefy the prey’s internal tissues, which the spider then sucks up using its pharynx and sucking stomach. The chelicerae and fangs pierce the prey, facilitating fluid injection. Some spiders may also masticate prey while applying digestive juices, particularly tarantulas, which can leave indigestible remnants.
Hydration is a necessity for spiders, who obtain water from various sources. They can drink directly from dew, raindrops, or small puddles. Spiders possess specialized mouthparts, including their chelicerae, which they can submerge to draw water into their digestive system. Additionally, spiders can absorb moisture from the air, especially in humid environments, and extract water from prey’s body fluids. While some species can survive extended periods without direct water intake, regular access to moisture is important for survival.