House spiders eat small insects and other arthropods that share your living space. Fruit flies, mosquitoes, moths, ants, and other tiny bugs that wander into a web or cross a spider’s path make up the bulk of their diet. Some species also eat other spiders, including members of their own kind.
Common Prey Found Indoors
The insects house spiders catch depend on what’s available in your home. Fruit flies are one of the most common meals, especially in kitchens. Mosquitoes, gnats, clothes moths, earwigs, cockroach nymphs, and ants are all fair game. Essentially, if a small bug blunders into a web or wanders near a hunting spider, it becomes food.
Different spider species catch prey in different ways, which shapes what they end up eating. Web-building species like the common house spider (the small brown ones that build messy cobwebs in corners) rely on insects flying or walking into their silk. They tend to catch whatever stumbles in. Jumping spiders, the compact, big-eyed spiders you sometimes see on windowsills, actively stalk their prey and can take on relatively large insects for their size. Cellar spiders, the long-legged ones that hang upside down in basements, are generalists that trap anything from gnats to beetles.
Spiders That Eat Other Spiders
Some of the most common indoor spiders are also spider hunters. Cellar spiders (often called daddy longlegs, though they’re not the same animal) actively invade the webs of other spider species and eat the residents. This spider-on-spider predation is common enough that biologists have a term for it: araneophagy.
Cannibalism also happens. When food is scarce, cellar spiders will eat their own kind. This isn’t unusual behavior in the spider world. Juvenile spiders of many species cannibalize siblings shortly after hatching, and in some families this tendency is more pronounced than others, suggesting it’s partly inherited. For house spiders, eating a rival means eliminating competition for the same food supply while gaining a meal.
How Spiders Eat Without Chewing
Spiders can’t chew or swallow solid food. Instead, they digest their meals outside their bodies before drinking them. The process starts with venom. When a spider bites its prey, the venom disrupts nerve-muscle signals, causing paralysis within seconds for small insects. The venom also begins breaking down the prey’s internal tissues chemically.
Once the prey is immobilized, the spider regurgitates enzyme-rich stomach fluids over and into the body. These digestive juices, combined with the venom and sometimes a grinding action from the spider’s jaw structures, reduce the insect’s soft tissues to liquid. The spider then sucks up this nutrient-rich fluid through its tube-like mouth, powered by a pumping stomach. What’s left behind is a dried husk of the insect’s outer shell. If you’ve ever noticed tiny, hollow insect bodies in a cobweb, that’s the aftermath of this process.
Some species, like flower spiders, are especially tidy eaters. They inject digestive fluids through a small bite wound and suck out the liquefied insides, leaving a prey husk that looks almost perfectly intact from the outside.
How Often They Need to Eat
House spiders don’t need daily meals. Most can survive 30 to 60 days without eating at all, which explains why spiders persist in rooms and corners where you rarely see any insects. Larger spiders with bigger fat reserves and slower metabolisms can go even longer. Even baby spiders, freshly hatched, come equipped to survive extended periods without food, nearly matching the starvation endurance of adults.
When food is available, a house spider might catch and eat a few insects per week, but there’s no fixed schedule. They’re opportunistic. A spider in a productive web near a kitchen light might eat several times a day during fruit fly season, while one tucked behind a bookshelf might go weeks between meals. This flexibility is one reason house spiders do so well indoors, where prey can be unpredictable.
Where They Get Water
Spiders need water more urgently than food, and most house spiders get a significant amount of moisture from the prey they consume. The liquefied insect tissues they drink contain enough water to sustain them in many cases. Some species can go their entire lives without drinking water directly, relying entirely on their food for hydration.
When prey is scarce, though, spiders seek out other water sources. Indoors, this means condensation on pipes, moisture in bathrooms, droplets on window glass, or dampness in basements. Spiders have been observed drinking dew collected on their own webs. Access to water significantly extends how long a spider can survive without catching any prey, which is why you tend to find house spiders concentrated in bathrooms, kitchens, and basements rather than dry upstairs rooms.
What a Spider in Your Home Tells You
A house spider’s presence is a reliable indicator that small insects are nearby, even if you don’t notice them. Spiders go where the food is. If you’re seeing spiders regularly in a particular room, there’s likely a population of tiny flies, ants, or other insects sustaining them. A single house spider can consume dozens of nuisance insects over its lifetime, making them one of the more effective forms of passive pest control in a home.
Spiders that aren’t catching enough food will eventually relocate, build new webs in more promising spots, or die. Abandoned webs collecting dust in a corner usually mean the spider moved on to better hunting grounds elsewhere in the house.