What Do Small Spiders Eat? A Diet Beyond Just Insects

Small spiders eat a remarkably varied diet that stretches well beyond the flies and gnats most people picture. While insects do make up the bulk of what most small spiders consume, research over the past few decades has revealed that many species regularly feed on pollen, nectar, fungal spores, other spiders, and even carrion. One jumping spider in Central America gets over 90 percent of its diet from plant structures, and common garden orb-weavers derive roughly a quarter of their nutrition from pollen grains caught in their webs. The menu is stranger and broader than it first appears.

The Insect Baseline

Most small spiders are generalist predators. They eat whatever small arthropods they can catch or stumble upon, and for web-building species that means a steady stream of tiny flies, gnats, aphids, midges, and small wasps or bees that blunder into silk. Hunting spiders like jumping spiders and wolf spiders actively stalk and pounce on similar prey, sometimes tackling items nearly their own body size. This much has been understood for centuries. What has changed is the recognition that “predator” does not mean “exclusively insectivorous.” Small spiders supplement their diet with plant-based foods, fungi, and other unconventional resources far more often than older textbooks acknowledged.

Pollen as Real Food, Not Accidental Snacking

Orb-weaving spiders build sticky spiral webs designed to catch flying insects, but those same sticky threads also trap enormous quantities of airborne pollen. For a long time, researchers assumed any pollen a spider ingested was accidental, swallowed as a byproduct of recycling old silk. That assumption turned out to be wrong. Experiments with the orb-weaver Araneus ceropegia showed that about a quarter of the spider’s diet consisted of pollen, with the rest coming from small flies and wasps. The proportion was similar whether the spiders were observed in the lab or sampled in the field, which suggests that pollen consumption is a deliberate dietary strategy, not a laboratory artifact.

Most pollen grains are too large to pass through a spider’s narrow throat opening, so they cannot be swallowed whole. Instead, spiders use the same extraoral digestion they apply to insect prey: they flood the pollen grain with digestive enzymes, dissolve its outer coating, and suck up the nutrient-rich liquid inside.

1PLOS ONE. Herbivory in Spiders: The Importance of Pollen for Orb-Weavers

The payoff for spiderlings is dramatic. Early work on the European garden spider Araneus diadematus found that access to pollen doubled the life expectancy of young spiders compared to fasting controls. Pollen-fed spiderlings also spun webs more frequently, which in turn improved their chances of catching insect prey.

2PubMed. Pollen feeding in an orb-weaving spider

Fungal spores get swept up by the same mechanism. Airborne spores stick to viscid web threads and are ingested when the spider eats its old silk before building a new web. Lab experiments with Araneus diadematus confirmed that spiders do take in fungal spores this way, adding yet another non-insect item to the orb-weaver menu.

3The Journal of Arachnology. Fungus and fruit consumption by harvestmen and spiders (Opiliones, Araneae): the vegetarian side of two predominantly predaceous arachnid groups

Nectar, Plant Bodies, and the World’s Most Vegetarian Spider

Pollen and fungal spores are passive catches, trapped by webs the spider already builds for insect prey. But some small spiders actively seek out plant-based food. Jumping spiders in the genera Eris and Metaphidippus were observed collecting nectar from the extrafloral nectaries of the plant Chamaecrista nictitans. When given a choice in controlled experiments, foraging spiders spent 86 percent of their time on plants with active nectaries rather than on identical plants without nectar. These spiders were still catching insects, ants, and even other spiders on the same plants, but nectar was clearly part of the draw.

4PubMed. Jumping spiders (Salticidae) enhance the seed production of a plant with extrafloral nectaries

The most extreme example of plant-eating in spiders is Bagheera kiplingi, a Central American jumping spider named after the panther in The Jungle Book. Two independent research groups found that this species feeds almost exclusively on the Beltian bodies produced by acacia trees. Beltian bodies are small, nutrient-rich structures the tree normally grows to feed its symbiotic ant guardians. At the study site in Mexico, Beltian bodies made up over 90 percent of the spider’s observed food intake. Isotope analysis confirmed the spider had a predominantly vegetarian diet, ruling out the possibility that plant material was just an occasional snack between insect meals.

5Current Biology. Nutritional Ecology: A First Vegetarian Spider

Bagheera kiplingi remains an outlier. No other known spider comes close to that level of herbivory. But the broader pattern is consistent: many jumping spiders and orb-weavers incorporate plant-derived nutrients into their diet to varying degrees. The notion that all spiders are strict carnivores is outdated.

Spiders That Eat Other Spiders

If you are a small spider, one of your most dangerous predators is another spider. Spider-on-spider predation is common across many families, but some species have made it their primary lifestyle. Pirate spiders in the family Mimetidae are specialized spider-hunters that invade the webs of other species, vibrate the silk to mimic struggling prey, and ambush the web’s owner when it comes to investigate. Studies of pirate spiders in New Zealand and Queensland found that they subdued their victims with a fast-acting venom that appeared to be specifically effective against other spiders, and held their prey in a “basket” formed by their spine-covered legs.

6Journal of Zoology. The biology of New Zealand and Queensland pirate spiders (Araneae, Mimetidae): aggressive mimicry, araneophagy and prey specialization

Not all spider-on-spider interactions end in a kill. Some small spiders are kleptoparasites, meaning they steal food rather than catching their own. Spiders in the genus Argyrodes live on the webs of much larger spiders like the giant wood spider Nephila maculata, snatching small prey items the host spider ignores or hasn’t noticed. One species, Argyrodes lanyuensis, takes this further by actually stealing silk from the host web, reducing the host’s orb by an average of 21 percent. The stolen silk gets repurposed for the parasite’s own use.

7PubMed. Silk stealing by Argyrodes lanyuensis (Araneae: Theridiidae): a unique form of kleptoparasitism

For very small spiders, this freeloading strategy makes practical sense. Building a web from scratch costs energy and protein. If you can live on someone else’s web, eat their leftovers, and pilfer their silk when they are not paying attention, you save on all three.

Indirect Blood-Feeding Through Mosquitoes

One of the stranger dietary specializations belongs to Evarcha culicivora, a jumping spider from East Africa. This species feeds indirectly on vertebrate blood by preferentially hunting blood-fed female mosquitoes, and it specifically targets mosquitoes in the genus Anopheles, which are the primary vectors of malaria. Earlier experiments had demonstrated the preference using computer animations and lures made from dead prey, but follow-up work confirmed that E. culicivora makes the same choice when offered living mosquitoes. The spider can apparently distinguish blood-fed females from unfed ones and from male mosquitoes, and this preference is unique to the species: other East African jumping spiders tested alongside it showed no such selectivity.

8PubMed. Evarcha culicivora chooses blood-fed Anopheles mosquitoes but other East African jumping spiders do not

The spider does not drink blood directly; it gets its blood meal secondhand, by digesting the mosquito’s blood-filled gut along with the rest of the mosquito. It is a predator of insects in the literal sense, but its nutritional target is vertebrate blood, making it functionally more like a parasite that outsources the biting to its prey. The preference for Anopheles over other mosquito genera is especially notable because researchers have explored whether the spider might play a role in local mosquito control, though the practical applications remain speculative.

Carrion and Scavenging

Spiders are generally thought of as predators that eat only freshly killed prey. The reality is messier. The cobweb spider Theridion evexum provides a striking example. Researchers observed that mother spiders stored dead insect prey for up to a week before their spiderlings emerged from the egg sac, then continued feeding the young rotten insects for about six weeks until they had molted several times. In a controlled experiment, spiderlings survived and molted successfully on a diet of exclusively rotten insects.

9Journal of Arachnology. Carrion Feeding By Spiderlings Of The Cob-Web Spider Theridion evexum (Araneae, Theridiidae)

This was the first documented case of carrion feeding in spider young. It challenges the assumption that spiders need live or freshly killed prey to survive, at least during their earliest developmental stages. For a spiderling that is too small and weak to capture its own prey, rotting insect leftovers provided by the mother may be a crucial bridge to independence. The implication is that small spiders, especially in their first weeks of life, can be scavengers as well as predators.

How Nutritional State Shapes What Spiders Choose to Eat

Small spiders do not just eat whatever crosses their path. There is growing evidence that their current nutritional state influences which prey they prefer. A study of Heliophanus jumping spiders tested whether previous diet affected the spider’s choice between two types of prey: aphids and other, smaller spiders. Spiders that had been fed a lipid-rich diet beforehand strongly preferred aphids. Those on protein-rich or standard diets did not show a clear preference one way or the other.

10Oxford Academic (Environmental Entomology). The nutritional status of Heliophanus spiders shifts their food preferences for aphid prey over intraguild spider prey

The finding suggests that spiders can sense, at least roughly, what nutrients they are lacking and adjust their hunting behavior to compensate. Aphids are relatively high in sugars and carbohydrates compared to other spiders, which are essentially bags of protein. A spider already loaded with fat and lipid may seek out the carbohydrate-heavy option rather than more protein. This kind of nutrient-balancing behavior has been documented in other arthropods, but seeing it in spiders reinforces how flexible their foraging strategies can be.

For anyone watching small spiders in a garden or home, this means the spider on your windowsill might be choosing between the fruit fly and the mite for reasons that go beyond mere opportunity. Its nutritional history shapes its preferences in real time.

The Gut Microbiome Connection

Small spiders rely on a community of gut bacteria to help process what they eat, and the functional profile of that microbiome hints at just how diverse spider diets can be. A large comparative study of wild-caught spiders across four different families found that their gut microbiota were involved in metabolism of carbohydrates, amino acids, cofactors, and vitamins, as well as the biosynthesis of fatty acids and lipids. These metabolic pathways were present in all four spider families studied.

11PLoS One. Interspecific variation and functional traits of the gut microbiome in spiders from the wild: The largest effort so far

The carbohydrate metabolism finding is especially interesting given that spiders are traditionally classified as strict carnivores. A pure meat diet should not require heavy-duty carbohydrate processing. The presence of these pathways in wild spiders is consistent with all the field observations described above: orb-weavers eating pollen, jumping spiders drinking nectar, spiderlings consuming fungal spores along with recycled silk. The gut bacteria appear to be equipped for a diet that mixes animal protein with plant-derived sugars and starches, which aligns with a far more omnivorous reality than the textbook image of a spider as a pure predator.

What Tiny Spiders Eat in Your Home

If you have noticed small spiders indoors, their diet depends on species and location. Cobweb spiders in corners and behind furniture catch a steady diet of gnats, fruit flies, clothes moths, small beetles, ants, and other household arthropods. Cellar spiders, the long-legged spiders common in basements, eat similar prey and are known to invade the webs of other spiders, killing and eating the occupant in the same pirate-spider fashion described in their wild relatives. Jumping spiders on windowsills hunt by sight and tend to take down flies, mosquitoes, and other small spiders.

House dust mites are often listed as spider prey, but the situation is more nuanced. Most house spiders are web-builders, and dust mites live in carpets and bedding rather than flying into webs. Ground-hunting spiders and very small species that forage at floor level are more likely to encounter and eat mites, springtails, booklice, and other micro-arthropods that live in household dust. These are some of the smallest prey items a spider can take, but for a spiderling measuring a millimeter or two across, they are a perfectly sized meal.

People sometimes worry that a spider in their home is not getting enough to eat, especially if it lives in a relatively clean room with few visible insects. Research on pollen feeding and carrion tolerance suggests that small spiders are more resourceful than they look. A web-building spider near a window may be supplementing its insect catches with pollen and fungal spores trapped in the silk. And as the Theridion evexum research showed, even dead and decaying insect material can sustain young spiders for weeks. The little spider in your ceiling corner is probably doing fine.

Why the “All Predator” Myth Persists

Spiders do rely on animal prey for the majority of their protein and energy in most species. That part is not wrong. The myth is in the word “exclusively.” For decades, any observation of a spider eating pollen or nectar was dismissed as an oddity or laboratory artifact, partly because spider feeding behavior is difficult to observe in the field. Spiders eat by liquefying their prey externally and sucking up the fluid, which means the evidence of a pollen meal looks identical to the evidence of a fly meal: a tiny ball of dry leftovers. Isotope analysis and controlled feeding experiments were necessary to demonstrate that plant-derived nutrients were genuinely being assimilated into spider tissues rather than just passing through.

The taxonomic bias is also relevant. Most spider dietary research has historically focused on large, conspicuous species. Small spiders, especially spiderlings, are harder to observe and harder to keep alive in the lab. The species where plant feeding has been most convincingly documented tend to be small orb-weavers and jumping spiders, precisely the groups that were understudied for the longest time. As more researchers turned their attention to small spiders and used modern analytical tools, the dietary picture expanded rapidly. The story of spider diets is still being written, but the direction is clear: the smaller and more closely you look, the more varied the menu becomes.