Tiny spiders living in your house eat whatever small arthropods they can catch or stumble upon, and that menu is surprisingly varied. Flies, gnats, mosquitoes, fruit flies, ants, mites, and even other spiders all end up as meals. The indoor environment offers fewer prey options than the outdoors, but houses are far from empty when you look at them through a spider’s eyes. What a particular spider eats depends on its size, its hunting method, and where in your home it has set up shop.
The Typical Indoor Menu
The most common food for tiny house spiders is small flying insects. Houseflies top the list in many homes. A study of gray wall jumping spiders in residential buildings in southern Mexico found that they primarily preyed on houseflies, visually locating them and capturing them with precise jumps from walls and ceilings.1Brazilian Journal of Science. Diet and hunting behavior of the gray wall jumping spider Menemerus bivittatus (Araneae: Salticidae) in homes in southern Campeche, Mexico That pattern holds for many indoor spider species: wherever flies congregate, spiders follow.
Beyond houseflies, tiny spiders regularly eat fruit flies (especially around kitchens), fungus gnats drawn indoors by potted plants, drain flies that breed in standing water, and mosquitoes. Small moths, midges, and the occasional winged ant round out the airborne portion of the diet. If you have ever noticed a cobweb in a window corner with a few dried insect husks clinging to it, you are looking at the remains of several meals.
Crawling prey matters too. Tiny spiders that hunt on floors and baseboards catch springtails, booklice, carpet beetle larvae, silverfish nymphs, and small ants. These ground-level meals are especially important for spiders too small to handle a full-grown housefly. A spider with a body barely two millimeters long is not going to wrestle an adult fly, but a springtail or a booklice the size of a grain of sand is a perfect match.
Mites and Microscopic Prey
One food source people rarely think about is dust mites and other microscopic arthropods. Your house is full of them. Research on house dust has found that mite densities can reach around a hundred mites per gram of dust in some homes, with the highest concentrations typically found in bedrooms and living rooms.2PubMed. Mite fauna in the home and sensitivity to house-dust and storage mites The dominant species tend to be dust mites from the genus Dermatophagoides in lived-in homes, though storage mites, oribatid mites, and other species also show up, especially in kitchens and bathrooms.3Building and Environment. Fungi, mites/ticks, allergens, and endotoxins in different size fractions of house dust from long-term uninhabited houses and inhabited houses
For the smallest house spiders, these mites represent a meaningful food source. Spiderlings fresh out of the egg sac are often barely visible to the naked eye, and they need prey that matches their scale. Dust mites, storage mites, and the tiny springtails living in carpet fibers and under furniture are exactly that. You will never see these meals happening because both predator and prey are too small to notice without magnification, but this hidden ecosystem supports the earliest life stages of many indoor spider populations.
How Tiny House Spiders Catch Their Food
The hunting method depends entirely on the type of spider, and houses tend to host two main groups: web builders and active hunters.
Web builders are the ones you notice most. Cobweb spiders (family Theridiidae), including the common house spider Parasteatoda tepidariorum, spin messy, irregular webs in corners, behind furniture, and along window frames. These webs function as passive traps. Insects blunder into the sticky silk, get tangled, and the spider rushes over to deliver a venomous bite. The beauty of this strategy indoors is that it requires very little energy. The spider builds the web once, makes repairs as needed, and waits. If the web catches nothing for days, the spider can relocate to a more productive spot.
Cellar spiders (Pholcidae), the long-legged spiders that hang upside down in basements and closets, build loose, wispy webs but use them differently. When prey or a threat touches the web, a cellar spider vibrates its body rapidly, blurring itself into near-invisibility while simultaneously wrapping the prey in silk. Cellar spiders are also well known for invading other spiders’ webs and eating the owners, which makes them effective predators of other indoor spider species.
Active hunters take a completely different approach. Jumping spiders (family Salticidae) are the most common indoor example. These small, often colorful spiders have excellent vision and stalk their prey the way a cat stalks a bird, creeping close and then pouncing. The gray wall jumping spider studied in Mexican homes used house walls as foraging areas, taking advantage of the frequent presence of flies and other insects associated with human dwellings.1Brazilian Journal of Science. Diet and hunting behavior of the gray wall jumping spider Menemerus bivittatus (Araneae: Salticidae) in homes in southern Campeche, Mexico If you have ever watched a tiny spider on your wall suddenly leap at something, that was almost certainly a jumping spider catching a meal.
Ground hunters like wolf spiders (Lycosidae) sometimes wander indoors too, usually by accident. These are generally larger than the typical “tiny” house spider, but juveniles can be quite small. They hunt by running down prey on the floor, and they eat whatever crawling insects and spiders they encounter.
When Prey Is Scarce
Indoor environments can be feast or famine for a spider. A kitchen with open fruit attracts fruit flies, and a spider near that fruit bowl eats well. A rarely used guest bedroom might offer almost nothing. Spiders have several ways of coping with lean times.
First, they are remarkably good at going hungry. Many small spider species can survive weeks without food, and some can last months by slowing their metabolism. This is part of why spiders succeed indoors in the first place: they do not need to eat every day, or even every week. A house spider that catches one decent-sized fly every week or two is doing fine.
Second, some spiders supplement their diet with non-insect food. Research on juvenile orb-weaving spiders found that pollen grains caught on sticky web spirals doubled the life expectancy of spiderlings compared to those that went without food entirely. The pollen-fed spiderlings also spun webs more frequently than fasting ones, suggesting they had enough energy to stay active.4PubMed. Pollen feeding in an orb-weaving spider Indoor air carries pollen, fungal spores, and fine organic particles, and web-building spiders inadvertently collect all of it. While pollen alone is not enough to sustain an adult spider, it can keep very young spiders alive through periods when insect prey is hard to come by. Fungal spores, interestingly, did not provide the same nutritional benefit and may even be harmful to spiderlings.
Third, spiders eat each other. Cannibalism is common in spiders generally, and in the tight quarters of a house with limited prey, a smaller spider becomes a meal for a larger one. Cellar spiders are particularly aggressive about this, regularly preying on cobweb spiders and other species that share their habitat.
How Indoor Lighting Shapes the Food Supply
If you have ever noticed more spider webs near light fixtures, porch lights, or windows, that is not a coincidence. Artificial lighting draws insects, and spiders go where the food is. Laboratory experiments with juvenile nocturnal orb-web spiders showed that they were attracted to LED lights when choosing foraging sites. Field experiments went further, revealing a significant increase in prey capture rates for webs placed near LED lights.5Ethology. Guiding lights: Foraging responses of juvenile nocturnal orb‐web spiders to the presence of artificial light at night The spiders are not attracted to the light itself so much as they have learned, in an evolutionary sense, that light means insects.
This finding has real implications for your home. Rooms with lights left on at night, especially near windows or exterior doors, attract more flying insects indoors. More insects means better hunting for spiders, which means those spiders survive longer, reproduce more, and become more visible. If you are trying to reduce spider activity in a particular room, managing artificial light at night is one lever you can pull. Switching to yellow or warm-toned bulbs near entry points also helps, since those wavelengths attract fewer flying insects than cool white or blue-toned LEDs.
Spiders as Free Pest Control
The question of what tiny spiders eat naturally leads to the question of whether you should let them. The answer depends on your comfort level, but the pest-control value of indoor spiders is genuine. In houses in South Africa, spiders were used successfully as biological control agents against flies.6Journal of Applied Entomology. Spiders in natural pest control: A review That is an unusually deliberate example, but the same dynamic plays out passively in homes everywhere. A few cobweb spiders in your basement are quietly intercepting moths, gnats, and mosquitoes that would otherwise bother you.
Jumping spiders hunting on your walls are picking off flies and other insects you might not even see. The gray wall jumping spider research specifically noted that the species contributed to natural control of synanthropic insects, the technical term for bugs that thrive alongside humans.1Brazilian Journal of Science. Diet and hunting behavior of the gray wall jumping spider Menemerus bivittatus (Araneae: Salticidae) in homes in southern Campeche, Mexico Whether you find that reassuring or unsettling is a personal matter, but the functional relationship is clear: a few small spiders in a house reduce the population of insects that most people find far more annoying.
Why Some Rooms Have More Spiders Than Others
Spiders do not distribute themselves randomly through a house. They concentrate where food, moisture, and shelter intersect. Bathrooms and kitchens often host more spiders than you would expect, partly because drain flies and fungus gnats breed in those wet environments, providing a reliable food source. Basements attract spiders because they tend to be undisturbed, slightly damp, and full of crawling insects like silverfish, sowbugs, and ground beetles.
Cluttered areas also favor spiders. Boxes, stored clothing, and stacked items provide structural complexity that spiders need for web attachment points and hiding spots. A tidy closet with bare walls offers nothing for a cobweb spider to anchor to, while a cluttered garage is ideal. If you want fewer spiders in a room, reducing clutter and fixing moisture problems removes both shelter and the prey insects that moisture attracts.
Window frames deserve special mention. The gap between glass and frame is a prime spot for tiny spiders because it concentrates prey. Insects are drawn to the light coming through windows, get trapped in the frame area, and walk straight into waiting webs. You will often find the husk-littered remains of multiple webs layered in the corners of window frames, evidence that several generations of spiders have worked the same productive territory.
Seasonal Shifts in Indoor Spider Diets
What tiny house spiders eat changes over the course of the year, at least in temperate climates. In spring and summer, when windows are open and insect populations peak, indoor spiders have access to a wider range of flying prey. Moths, mosquitoes, crane flies, and gnats wander inside regularly, and spiders eat well. This is also when young spiders hatch and grow quickly, supported by abundant food.
In autumn, many outdoor spiders move indoors seeking shelter, which temporarily increases both spider numbers and competition for prey. The insects available in fall skew toward cluster flies, stink bugs, and the last mosquitoes of the season. By winter in colder climates, the prey supply drops dramatically. Flying insects become rare indoors, and the spiders that survive the lean months are the ones that caught enough food earlier to build up energy reserves, or the ones that can subsist on ground-level prey like springtails and mites, which remain active year-round in heated homes.
The pollen-feeding research is relevant here, too. The study found that juvenile orb-weavers appear in spring when insect prey is scarce but airborne pollen is abundant, suggesting that microscopic organic matter serves as the primary food source for very young spiders during that transitional period.4PubMed. Pollen feeding in an orb-weaving spider Indoors, a similar dynamic likely occurs: spiderlings that hatch during a low-insect period can survive on whatever organic debris their webs collect until more substantial prey becomes available.
Spiders That Eat Other Spiders
One aspect of indoor spider feeding that surprises people is how often spiders eat each other. This is not limited to different species. Cannibalism within the same species happens regularly, especially when food is limited and individuals are different sizes. A slightly larger spider will not hesitate to eat a slightly smaller one if the opportunity arises.
Cellar spiders are the most aggressive intraguild predators among common house spiders. They routinely enter the webs of cobweb spiders, overpower them, and consume them. This behavior makes cellar spiders something of a top predator in the indoor spider food web. If you notice that one type of spider seems to dominate a particular room while others have disappeared, predation rather than competition for food is often the explanation.
Some spider species also deliberately target spider egg sacs, eating the eggs or the newly hatched spiderlings inside. From a nutritional standpoint, egg sacs are a concentrated package of protein and fat, and for a tiny spider, raiding one is far easier than catching flying insects. This kind of predation helps regulate indoor spider populations naturally, preventing any one species from completely dominating a home.