Cellar Spider vs Brown Recluse: How to Tell Them Apart

Short answer

• A cellar spider and a brown recluse can look alike in a quick glance, because both are brownish spiders found in houses, but they separate cleanly once you check more than color. Start with the legs and the web. A cellar spider has extremely long, thin, delicate legs that dwarf its small body, and it almost always sits in a loose, tangled web in a corner. A brown recluse has shorter, sturdier, uniformly colored legs with no bands or stripes, a compact body, and no open web you would readily see. With magnification, the eyes give a sharper test. A brown recluse has six eyes in three pairs, while the cellar spiders most often found in homes have eight eyes. Do not rely on a violin shaped mark alone, because many spiders carry a dark mark on the front part of the body. Use several features together, observe from a safe distance, and do not handle a spider you cannot identify.

Why these two spiders get confused

Both spiders are brown, both turn up indoors in basements, garages, and quiet corners, and both can show a darker mark on the front part of the body. Colorado State University Extension notes that cellar spiders are sometimes mistaken for brown recluses because patterning on the body can superficially resemble the violin pattern notable on the brown recluse. That resemblance breaks down as soon as you look at proportions, legs, eyes, and webs. Names add confusion too. Cellar spiders are often called daddy longlegs spiders, but that name is also used for harvestmen, which are arachnids in a different order and are not spiders at all, a distinction Colorado State University Extension makes explicitly. Photographs mislead for a third reason. A close photograph flattens depth, hides leg length, and removes the web, posture, and habitat, which are often the most useful clues. Treat a single photograph as a starting point, not a verdict.

At a glance

Feature	Cellar spider	Brown recluse
Body	Small, longer than wide, long cylindrical abdomen in the longbodied species	Compact, uniformly colored abdomen, no patterning
Legs	Extremely long, thin, delicate, darker joints in some	Proportionate, silky, uniform color, no bands, no large spines
Eyes	Eight, often two groups of three with a pair between	Six, in three pairs, in a semicircle
Front mark	Gray mark in the center of the carapace, can resemble a violin shape	Usually a violin shaped mark, but contrast varies, not reliable alone
Web	Almost always in a loose, irregular web in a dark corner	No open web readily seen, daytime retreats are web lined
Habitat	Dark corners of basements, garages, outbuildings, hanging upside down	Dark crevices and hollows, basements where common
When disturbed	Often bounces or vibrates in the web	Active at night, hides in retreats by day

The cellar spider: body, legs, and posture

The longbodied cellar spider, Pholcus phalangioides, is the most common cellar spider in the United States, according to Penn State Extension. Penn State Extension gives females at 7 to 8 millimeters and males at 6 millimeters in body length, with a very wide carapace and an abdomen about three times as long as it is wide and cylindrical in shape. Utah State University Extension describes the same form as long delicate legs with a small, elongate or globular body, pale tan or yellow with a gray mark in the center of the carapace.

The legs are the first feature most readers notice. Penn State Extension gives the forelegs of an adult female at about 50 millimeters, roughly six to seven times the body length, which explains the spindly, threadlike silhouette. Joints may look darker, giving a knobby kneed look, and the spider often hangs upside down in its web with legs spread wide, so the body looks smaller still. A brown recluse never presents that silhouette, because its legs are proportionate and its body looks compact beside a cellar spider. Colorado State University Extension lists the longer than wide body form as a feature that readily distinguishes commonly encountered cellar spiders from recluses. Color is the weakest clue, because it varies with species, age, and light, while leg proportion and web association vary far less.

The brown recluse: body, legs, and posture

The brown recluse, Loxosceles reclusa, belongs to the recluse genus Loxosceles. Colorado State University Extension describes the body color as brown, ranging from light to dark brown, with a uniformly colored abdomen without patterning. Virginia Tech Cooperative Extension gives a similar description, tan to dark brown, often golden brown, generally uniform, with no stripes or bands on the legs, and a body measuring 8 to 10 millimeters long, about 0.4 inch. The University of Tennessee Extension publication gives a slightly wider range of 7 to 12 millimeters, so a single size figure should not be treated as exact. Body length means the body only, not the legs, and the legs spread across an area roughly the size of a quarter at rest.

Recluse legs carry negative clues, meaning clues based on what is absent. Colorado State University Extension states that recluse legs are long and thin, silky in appearance because of fine hairs, uniform in color, never banded, with no large spines. Virginia Tech Cooperative Extension agrees: uniform color, no stripes or bands on the legs, and fine, not coarse, hairs. Clear bands, rings, stripes, or stout spines therefore rule a recluse out, whatever the color or mark may suggest. A recluse is active at night and hides by day in dark crevices and hollows, according to Colorado State University Extension. Both spiders favor dark, undisturbed places, but a cellar spider is usually visible in its web, while a recluse is usually hidden in a retreat and does not sit in an open web.

Eyes: the strongest single check, with a practical limit

Colorado State University Extension states that the quickest way to positively identify a recluse spider is to examine the arrangement of the eyes, and that there should be three pairs: one pair in front and the other two along the sides, forming a semicircle. Virginia Tech Cooperative Extension describes the same arrangement as six eyes in three groups of two, with a gap between each pair, and calls it an excellent way to identify a brown recluse, because most spiders have eight eyes in two rows.

Cellar spiders have eight eyes, often in two clusters of three with a pair between them, according to Colorado State University Extension. Penn State Extension gives a matching description for the longbodied species: two triads of larger, light colored eyes on top of the cephalothorax and a pair of dark, small eyes on the front. Counting eight eyes rules a recluse out. Counting six eyes in three well separated pairs gives strong support for a recluse, but still needs the other features, because a few other spiders also have six eyes. The practical limit is magnification. Colorado State University Extension notes that examining the eyes requires magnification, and Virginia Tech Cooperative Extension states that proper magnification requires a microscope, while a hand lens may help. Do not guess an eye count from a blurry photograph or a spider seen across a room. Virginia Tech Cooperative Extension advises submitting a spider suspected to be a brown recluse in alcohol to a local extension agent for identification.

The violin mark: useful, but not reliable alone

Colorado State University Extension states that brown recluse spiders usually have a violin pattern on the cephalothorax, the body region that includes the head and legs, with the eyes incorporated into the base of it. Virginia Tech Cooperative Extension describes the fiddle shaped pattern behind the eyes, usually dark brown or black, with the neck of the fiddle pointing toward the abdomen. The University of Tennessee Extension publication adds that the mark is usually much darker than the surrounding areas and may appear longitudinally lined, but in some individuals its size may be considerably reduced.

That variation is the first reason not to rely on the mark alone. Colorado State University Extension warns that its contrast can vary among recluse species and life stages, and that brown patterning on the cephalothorax also occurs in many other spiders, including funnel weavers and cellar spiders. A recluse can show a faint mark, and a non recluse can show a mark that looks like a violin. The Ohio State University Extension article makes the same point: the violin description is subjective, people mistake stripes or other patterns for the so called fiddle, and a better key is the eyes. Cellar spiders carry their own central mark, described by Penn State Extension and Utah State University Extension as a gray mark in the center of the carapace, which can read as a violin shape in poor light. In a recluse, the neck of the fiddle points toward the abdomen. Even when the direction fits, the mark still needs support from the eye count, uniform legs, and an unpatterned abdomen.

Legs, body surface, and the abdomen: the supporting checks

Three supporting features help confirm or overturn a first impression. First, leg patterning. Recluse legs are uniform, never banded, with no large spines, while cellar spider legs are extremely long and thin, with joints that may look darker. A banded leg fails the recluse test outright. Second, body surface. Recluse bodies carry fine hairs with a silky appearance, and Virginia Tech Cooperative Extension stresses that the hairs are fine, not coarse. A spider with coarse hairs, bristles, or stout spines does not fit the recluse description, though fine hairs alone do not separate the pair. Third, the abdomen. Colorado State University Extension describes the recluse abdomen as uniformly colored, without patterning, and Virginia Tech Cooperative Extension states that recluse spiders never have markings on the abdomen. A patterned abdomen, with spots, chevrons, bands, or a bold pale shape on top, is not a brown recluse. A long, cylindrical abdomen with a body longer than wide points toward the longbodied cellar spider, especially with very long legs and a web.

Webs and habitat

Cellar spiders are web spiders in the fullest sense. Colorado State University Extension states that they are found almost always in association with a web, in dark corners of basements, garages, and outbuildings. Penn State Extension describes an irregular mesh of threads, and Utah State University Extension describes irregular cobwebs near windows, over pipes, or all over the ceiling and walls, especially in corners. The female carries her eggs in her mouthparts as she hangs inverted in the web, according to Penn State Extension. When disturbed, cellar spiders often bounce or vibrate rapidly in the web, according to Colorado State University Extension and Penn State Extension, which makes the spider hard to see clearly. That behavior is a strong field clue, not a formal feature, but a spider that shakes its whole web and stays in it is behaving like a cellar spider, not a recluse.

Brown recluse webs work differently. Colorado State University Extension states that recluse webs are not produced in open areas where they are readily seen, and that daytime activity is restricted to web lined retreats. Virginia Tech Cooperative Extension agrees: recluses hide behind boards and boxes and do not make webs out in the open. A loose, visible cobweb in a ceiling corner, with a long legged spider hanging in it, therefore points away from a recluse before eyes or marks are checked. Habitat overlap is real. Both spiders favor dark, quiet, protected spots, and Penn State Extension lists cellars, warehouses, garages, and caves for the longbodied cellar spider. Shared habitat tells you where to look, not which spider you found. The web, posture, and proportions do that work.

Range: why location matters, and why it is often overstated

Range is the check most often skipped, and it most often overturns a recluse identification outside the core range. Colorado State University Extension states that the brown recluse occurs in many midwestern and south central states, and can be very common in and around homes in eastern Kansas, Missouri, Arkansas, Louisiana, Oklahoma, parts of Texas, and some other states. Read that as a general core range, not a precise map, because the same source notes that other recluse species occur in southwestern states and that species level identification can only be done by an expert.

Outside that core range, the picture changes sharply. Colorado State University Extension states that the brown recluse is extremely rare in Colorado, with only one specimen of Loxosceles reclusa in the Denver Museum of Nature and Science collection from the state, and that occurrence there is incidental, from occasional transfers from infested areas, with establishment much rarer, if it occurs at all. Penn State Extension makes a parallel point for Pennsylvania: outside their native range, brown recluses are restricted to buildings and almost exclusively brought in by humans, for example in household goods moved from a native area, and are therefore extremely rare and localized. Washington State University reporting quotes a university entomologist stating that the brown recluse does not live in the Northwest and dwells in the South and lower Midwest, and that spiders submitted as brown recluses from the Northwest had not, to date, turned out to be brown recluses. A peer reviewed range study summarized in PLOS ONE found that of 1,773 specimens submitted as Loxosceles reclusa, 79 percent did not belong to that species, and all but two genuine occurrences came from within the known area of distribution. Those figures are attributed to that study as summarized in PLOS ONE. By contrast, Penn State Extension describes the longbodied cellar spider as the most common cellar spider in the United States, found in many types of buildings throughout the year. Range does not prove an identification, because transported spiders do occur, but it sets the burden of proof. Outside the core range, a recluse claim needs the full checklist plus confirmation by an extension identification service.

A step by step check you can use without handling the spider

Work through these checks in order, from a safe distance, without picking the spider up. Stop as soon as a check rules one candidate out.

First, web and posture. A spider hanging in a loose, irregular web in a corner, with very long legs spread wide, fits a cellar spider. No visible open web, with the spider hidden in a crevice or retreat, fits a recluse better, but fits many other spiders too.

Second, leg length against body length. Legs several times longer than the body, thin and threadlike, with the body almost lost among them, mean a cellar spider silhouette. Legs long but proportionate, with a compact body, are closer to a recluse silhouette, but still need the checks below.

Third, leg bands and spines. Clear bands, rings, stripes, or stout spines rule a recluse out. Uniform color with fine hairs and no large spines keeps a recluse in play, and also keeps a cellar spider in play.

Fourth, the abdomen. Any bold pattern on the abdomen rules a recluse out. A plain, uniform abdomen keeps a recluse in play. A long, cylindrical abdomen with a body longer than wide points toward the longbodied cellar spider, especially with very long legs and a web.

Fifth, the front body mark, treated as a weak clue. A fiddle shape with its neck pointing toward the abdomen supports a recluse but does not prove one. A missing or faint mark does not rule a recluse out, because the mark varies and can be reduced.

Sixth, the eyes, if you can check them safely with magnification or a clear magnified photograph. Eight eyes rule a recluse out. Six eyes in three well separated pairs give strong support for a recluse when combined with uniform legs and a plain abdomen. If you cannot count the eyes clearly, do not guess. If the checks point in different directions, trust the stronger checks. Eyes and leg banding outweigh color and the violin mark. Web association and leg proportion outweigh habitat alone. When in doubt, record the location, the web, and a clear photograph from a safe distance, and ask a local university extension identification service to confirm it.

Common confusions beyond this pair

Three other spiders cause regular confusion with this pair. These notes are summaries only, with full profiles in their own Amberaisle articles, listed in the notes at the end of this draft.

The false black widow, covered in AMB-371, is a Steatoda spider, not a true black widow and not a recluse. It is a dark, rounded abdomen spider of tangled cobwebs, and confusion with a recluse usually comes from color and web type, not leg length or eyes. It lacks the extremely long, threadlike legs of a cellar spider, and it lacks the six eye recluse pattern and uniform recluse body plan. A dark, glossy, rounded spider in a cobweb should be compared with the false black widow profile before settling on either spider in this article.

The giant house spider, covered in AMB-193, is a large, brown, hairy funnel web spider. Confusion with a recluse comes mainly from size, color, and wandering males crossing floors in late summer and autumn. It is larger and hairier than a recluse, with banded or patterned legs and eight eyes, and it builds a funnel web rather than a loose cellar spider web or a hidden recluse retreat. Leg banding, hairiness, and web type separate it from both spiders here.

The male black widow, covered in AMB-140, is the confusion most likely to surprise readers, because a male looks nothing like the glossy black female most people picture. Males are smaller, browner or grayer, and more patterned, and they wander in search of females. That wandering, patterned, brownish male can be mistaken for a recluse, a cellar spider, or a false black widow, depending on which feature the reader notices first. The male black widow profile explains why sex matters in identification, and why a patterned brown spider on a floor is not automatically a recluse.

If you are unsure

Keep your distance, do not handle the spider, and note the web, the posture, and the location. Photograph the spider from a safe distance if you can do so without disturbing it, keeping the photograph sharp enough that leg length and body shape are visible. If you think you have been bitten by a brown recluse, seek professional medical help promptly. For identification alone, a local university extension service or museum identification service can examine a photograph or a safely contained specimen and give a firmer answer than a general web search. Do not rely on a single online photograph match, and do not assume that a brown spider in a house must be a recluse, because most brown house spiders are not.

Frequently asked questions

How can I tell a cellar spider from a brown recluse at a glance?

Look at the legs and the web first. A cellar spider has extremely long, thin legs that dwarf its small body, and it usually hangs upside down in a loose, tangled web. A brown recluse has proportionate, uniformly colored legs with no bands, a compact body, and no visible open web. Color alone will not separate them.

Do cellar spiders have the violin mark?

Cellar spiders can carry a central gray mark on the carapace that resembles a violin shape in poor light or in a close photograph, according to Penn State Extension and Utah State University Extension. Colorado State University Extension warns that cellar spider patterning can superficially resemble the recluse violin pattern. A central mark cannot identify a recluse by itself.

Do brown recluses always have a violin mark?

No. Colorado State University Extension states that brown recluse spiders usually have a violin pattern, and that its contrast can vary among species and life stages. The University of Tennessee Extension publication adds that the mark may be considerably reduced in some individuals. A missing mark does not rule a recluse out, and a bold mark does not prove one.

How many eyes does each spider have?

A brown recluse has six eyes in three pairs, arranged in a semicircle, according to Colorado State University Extension and Virginia Tech Cooperative Extension. Commonly encountered cellar spiders have eight eyes, often in two groups of three with a pair between them, according to Colorado State University Extension. Counting eight eyes rules a recluse out, but counting eyes reliably needs magnification.

Do brown recluses build webs in corners like cellar spiders?

No, not in the same way. Cellar spiders build loose, irregular webs in dark corners and hang in them, according to Colorado State University Extension, Penn State Extension, and Utah State University Extension. Brown recluse webs are not produced in open areas where they are readily seen, according to Colorado State University Extension, and daytime hiding places are web lined retreats.

Can a brown recluse live outside its normal range?

Occasionally, as a transported individual, but establishment outside the normal range is rare, according to Colorado State University Extension and Penn State Extension. Both sources describe out of range occurrences as incidental or restricted to buildings and brought in by humans, for example in household goods moved from a native area. A report from far outside the core range needs stronger evidence, ideally confirmation by an extension identification service.

What should I check first if I only have a photograph?

Check leg proportion and web context first, then leg banding and abdomen patterning, then the front body mark, and treat the eyes as decisive only if they are clearly visible with magnification. If the photograph is blurry, cropped so the legs and web are missing, or taken in poor light, the photograph is insufficient and expert identification is needed.

Sources & references

• Colorado State University Extension. Brown Recluse Spiders in Colorado: Recognition and Spiders of Similar Appearance. https://extension.colostate.edu/topic-areas/insects/brown-recluse-spiders-in-colorado-recognition-and-spiders-of-similar-appearance-5-607/
• Penn State Extension. Longbodied Cellar Spider. https://extension.psu.edu/longbodied-cellar-spider
• Penn State Extension. Brown Recluse Spiders. https://extension.psu.edu/brown-recluse-spiders
• Virginia Tech Cooperative Extension. Brown Recluse Spider. https://ext.vt.edu/content/pubs_ext_vt_edu/en/ENTO/ENTO-135/ENTO-135.html
• University of Tennessee Extension. The Brown Recluse Spider. https://solutions.tennessee.edu/?view_pub_pdf=1776
• Utah State University Extension. Cellar Spiders. https://extension.usu.edu/planthealth/ipm/notes_nuisance/cellar-spiders
• Ohio State University Extension. You Are a Mean One, Mr. Recluse? https://bygl.osu.edu/node/653
• Washington State University. WSU Scientist: Dreaded Spider Does Not Live Here. https://archive.news.wsu.edu/news/2013/06/18/wsu-scientist-dreaded-spider-doesnt-live-here/