The window ranges from days to several months, depending on which animal you are actually looking at. A well-fed harvestman can last four to ten weeks without another meal, a cellar spider can stretch that to two or three months if water is present, and an adult crane fly usually dies within five to fifteen days, with many never feeding at all.
Sorting through the confusion around harvestmen, cellar spiders, and crane flies, this guide breaks down how long each so-called daddy longlegs can actually survive without eating and what their bodies are doing in the meantime.
Sorting Out Which Creature Is Actually a Daddy Longlegs
One nickname covers three unrelated organisms, and the answer to how long any of them survives without food hinges on which animal is sitting in front of you. Body shape and segment count are the quickest way to tell them apart in the field.
Harvestmen (Opiliones)
Harvestmen are the arachnid most people picture when they say “daddy longlegs.” You can recognize them by a single rounded body, eight long thin legs, no silk, no venom glands, and no narrowing between body segments. They cluster on porch ceilings, garden walls, and the undersides of sheds. Their fused body shape is the fastest field marker: if it looks like a single pebble with legs glued on, you are looking at a harvestman.
Cellar Spiders (Pholcidae)
A clear waist separating cephalothorax from abdomen, plus silk glands and venom, confirms these arachnids as genuine spiders rather than something else. The longbodied cellar spider (Pholcus phalangioides) builds messy cobwebs in basement corners and ceiling joists. Their legs look delicate, but the body is unmistakably two-segmented. The legs match a harvestman’s for spindliness, yet the body plan is pure spider.
Crane Flies (Tipuloidea)
Two wings, six legs, and a mosquito-like silhouette place these insects firmly in the order Diptera, far removed from arachnids. One pair of wings, long legs that detach easily, and a slim body built for short adult flights set them apart. The nickname “daddy longlegs” or “mosquito hawk” attaches to adults near porch lights in late summer. They eat very little as adults, and most species barely feed, which is why their adult lifespan is measured in days.
| Common Name | Scientific Group | Body Segments | Key Feature |
|---|---|---|---|
| Harvestman | Opiliones | One fused oval | No silk, no venom |
| Cellar spider | Pholcidae | Two distinct segments | Cobwebs in corners |
| Crane fly | Tipuloidea | Insect body with wings | Flies to lights, legs detach easily |
What Their Bodies Are Doing Between Meals
Starvation tolerance starts with how much energy a small body burns just to stay alive. Ectotherms like harvestmen and cellar spiders set their pace by ambient temperature rather than internal heat, which keeps their caloric bill far lower than a mouse or a hummingbird would carry.
Low Daily Demand
A harvestman weighing roughly 15 milligrams has a daily energy budget that is a small fraction of a similarly sized insect’s. Most of the day is spent motionless on a wall, and active foraging rarely lasts more than a few minutes. That sluggish baseline stretches fat reserves much further between meals than the same grams of fat would stretch in a more active predator.
Flexible Activity Cycles
When prey gets scarce, harvestmen dial activity down further. They tuck legs in, stay on shaded surfaces, and skip the wandering that would otherwise burn glucose. Cellar spiders have an even easier time. They stay in the web and wait, only burning energy when something blunders into the silk. Both strategies extend the feeding gap without triggering immediate shutdown.
Because both groups conserve energy differently, the real question becomes how long either can stretch that gap before it matters.
How Long Different Daddy Longlegs Actually Last Without Food
Lab and field observations give workable ranges for each group, even though no single peer-reviewed study has pinned down exact day counts for every species. Expect weeks to a few months for the arachnids and days for the fly.
Harvestmen: Weeks to a Few Months
Healthy adult harvestmen typically survive four to ten weeks without food under typical indoor or sheltered outdoor conditions. Access to water droplets, morning dew, or damp surfaces extends that range, while dry conditions shrink it. Younger or recently molted individuals deplete faster because reserves are still being allocated to growth rather than stored as fat.
Cellar Spiders: Roughly Two to Three Months
Left alone in a quiet, slightly humid basement with a recent meal, a cellar spider can often survive roughly two to three months without catching prey. The web itself becomes part of the survival strategy, since old silk may snag tiny bits of organic debris and fungal spores that supplement a strict insect diet. Without any water, the same spider collapses within days to a couple of weeks.
Crane Flies: Days, Not Months
Most adult crane flies manage only five to fifteen days of life after emerging, with certain species struggling to survive even a full week. Many adults do not feed at all, or sip only traces of nectar. Their starvation clock is essentially the same as their total lifespan clock, so food deprivation rarely matters before something else ends them.
| Type | Without Food (with water) | Without Food or Water |
|---|---|---|
| Harvestman | 4–10 weeks | Days to ~2 weeks |
| Cellar spider | ~2–3 months | Days to ~2 weeks |
| Crane fly adult | A few days to 2 weeks | Under 1 week |
The Environmental Factors That Stretch or Cut Survival Time
Starvation survival is not a fixed number. Several environmental levers move it sharply up or down, and knowing them helps you predict when a basement dweller will finally give up.
Temperature and Metabolism
Cooler temperatures slow an ectotherm’s metabolism, which means stored fat burns slower. A harvestman in a 55°F basement outlasts the same species in a 75°F attic by a noticeable margin. Heat shortens the window; cool, stable conditions extend it.
Water Access
Water matters more than food for short-term survival. Hemolymph, the arthropod equivalent of blood, needs water to circulate nutrients and keep tissues viable. A harvestman can survive weeks without prey but only a few days without moisture. Leaky pipes, condensation on cold pipes, damp basement walls, and pet water bowls all act as survival support worth removing.
Age, Condition, and Recent Meals
A well-fed adult carries fat bodies that a starving or juvenile specimen simply does not have. Animals approaching a molt cycle are especially vulnerable, since molting burns through stored resources and leaves the soft new cuticle exposed. Disturbance levels also matter: a harvestman that keeps being brushed off the wall burns more energy fleeing than one tucked behind a storage box.
Remove the water source before you try to starve one out. Cutting off dampness in a basement often works faster than waiting for the creature to run out of fat reserves.
What They Normally Eat and Why That Flexibility Matters
Diet shape influences how well an animal bridges a long food gap. Specialists starve quickly because nothing matches their narrow menu. Generalists last longer because anything vaguely edible keeps the metabolism from crashing.
Harvestmen Are True Omnivores
Harvestmen eat decaying plant matter, fungi, soft-bodied insects, mites, bird droppings, and even small slugs. That dietary mix is the metabolic equivalent of a varied pantry. A harvestman stuck on a window ledge can nibble dust, fungal spores, and dead gnats drifting past, none of which would sustain a strict predator like a cellar spider.
Cellar Spiders Depend on Web-Caught Prey
Cellar spiders mostly take other spiders and small flying insects snared in cobwebs. When nothing hits the silk, they wait. Some species shake the web to mimic a struggling insect and lure prey closer, a sign that they are built for ambush rather than active hunting. Your entire feeding system is built around long quiet intervals, which is why fasting stretches so long.
Crane Fly Adults Barely Eat
Many adult crane flies do not feed at all. Those that do sip small amounts of nectar or honeydew. Larvae, by contrast, feed on roots, decaying vegetation, or aquatic detritus depending on species, and that is where the actual growth happens. Adult starvation tolerance is short simply because the adult stage was never designed to last.
That short adult stage is precisely why what they eat matters so little to your household.
What This Means for Your Home and Your Patience
Most readers land here with two practical concerns: whether sealing off a room will get rid of one, and how long until it stops being your problem. Both questions have honest answers.
Starving Them Out Is Slow, Not Instant
Seal a harvestman or cellar spider inside a room with no prey and expect weeks, not days. A realistic estimate is one to three months, depending on temperature, humidity, and the individual animal’s condition. Sealing cracks, removing webs, and cutting off water shortens that window considerably.
Water Removal Is the Fastest Lever
Fix the leaky pipe, run a dehumidifier, and wipe down condensation on basement windows. Dry air and no free water cuts survival time from months to weeks for cellar spiders, and from weeks to days for harvestmen.
Humane Removal Is Reasonable
Even the toughest of these creatures rarely makes it past a few months in ideal conditions, so a humane approach is both kind and effective. A cup and a piece of cardboard to scoop and release outdoors works fine. Most do not survive long outdoors either, but at least the choice belongs to the creature rather than a slow sealed-room starvation.
Clean Spaces Do Not Host Colonies
A single daddy longlegs wandering into a tidy kitchen did not establish a population. These creatures do not breed indoors the way German cockroaches or common house spiders can. If more keep appearing, your likely entry point is a gap around a pipe, a door sweep that does not seal, or a window screen with a tear worth fixing.
Putting It Together
Figure out which animal is actually in front of you, expect weeks to a few months of survival for harvestmen and cellar spiders when water is available, and remember that water deprivation collapses that window far faster than food deprivation ever will. Removing moisture and sealing entry points handles most household encounters without waiting out a starvation clock at all.
FAQ
How long can a daddy longlegs go without eating?
A well-fed harvestman typically lasts four to ten weeks without food, and a cellar spider can stretch that to roughly two to three months if water is available. Without any moisture, both collapse within days to a couple of weeks.
Do daddy longlegs need food to survive?
Yes, but far less often than most arthropods. Small body size, slow metabolism, and flexible diets (especially in harvestmen) mean a missed meal here and there has no real impact, and long fasts are physiologically survivable.
What do daddy longlegs eat in the wild?
Harvestmen take decaying plant matter, fungi, soft-bodied insects, and bird droppings. Cellar spiders rely on small insects and other spiders caught in their webs. Crane fly adults mostly sip nectar or do not feed at all.
Can daddy longlegs survive indoors without food?
Yes, and often for weeks to months depending on species, room temperature, and humidity. Indoor environments tend to stay stable enough that water access becomes the real survival bottleneck rather than prey availability.
Why do daddy longlegs seem to live so long in my house?
Basements and crawlspaces offer stable cool temperatures, steady humidity, and low disturbance, which together slow metabolism and conserve fat reserves. Remove any one of those factors and survival time drops sharply.
How often does a daddy longlegs need to feed?
Healthy adults in the wild typically feed every few days when prey is available, but they are built to handle long gaps without stress. Multiple weeks between meals is normal during cool or low-prey seasons.
