Brown Spiders with Big Butts: Identification and Bite Risks

Introduction

If you've noticed a brown spider lurking in your home or yard with a peculiarly large abdomen, it may have you wondering: what kind of spider is this? Most spiders have relatively small behinds, so a brown spider with a disproportionately big butt can be puzzling or alarming if you don't know what it is.

While most spiders you encounter are harmless, some big-bottomed brown spiders can deliver a nasty bite. So it's important to be able to identify them by their distinctive markings and behavior. This article will cover brown spiders with large abdomens that may be found around homes in the United States and tips on deterring them safely.

Brown Recluse Spider

One of the most infamous brown spiders known for its rotund behind is the brown recluse spider. Scientifically named Loxosceles reclusa, this spider ranges across central and southern parts of the United States.

The brown recluse has a brown body ranging from 14 to 34 inches long, with a large oval abdomen taking up much of its girth. A key identifier is the violin-shaped marking on its back, with the "neck" of the violin pointing toward the bulbous abdomen.

Other Identifying Traits

In addition to its large rump and fiddle-shaped marking, the brown recluse spider has these other identifying features:

• Uniform tan to dark brown color
• Six equal-sized eyes arranged in pairs
• Three pairs of legs with fine hairs
• Long, thin legs that are lighter in color
• No obvious stripe or pattern on legs

Behavior and Habits

As their name suggests, brown recluse spiders tend to be shy and reclusive. They prefer dark, sheltered spots like attics, garages and sheds. You may also find them hiding in piles of clothes, cardboard boxes, or nooks and crannies indoors.

These spiders are active at night when hunting prey. Despite their bulging bellies, they feed on fairly small insects and pests. Bites to humans usually happen when trapped against the skin rather than intentional attacks.

Risks of Bites

While shy, the brown recluse does have a venomous bite that can cause significant reactions in some people. However, bites are rare compared to the spider's wide geographical presence.

A brown recluse bite forms a small red mark that may later blister, ulcerate and turn black in the center. Pain, itching and swelling may occur. Serious symptoms like fever, rash, nausea and tissue damage are possible but uncommon.

Hobo Spider

Another brown spider known to have a plump abdomen is the hobo spider. Its scientific name is Eratigena agrestis. This species inhabits areas of the Pacific Northwest and northern states.

The hobo spider has an oval body reaching up to 5/8 inches long. The abdomen is disproportionately large, especially after feeding. The rest of the body is more slender by comparison.

Traits and Markings

In addition to the bulbous abdomen, the hobo spider has these identifying traits:

• Pale brown to dark brown color
• Chevron pattern on the abdomen
• Banded legs with short fine hairs
• Males have large pedipalps (mouthparts)

Habits and Behavior

The hobo spider tends to occupy moist, dark areas in and around homes. Common hiding spots include basements, crawl spaces, garages and sheds. Their large size may intimidate, but they are not aggressive.

These nocturnal hunters feast on small insects, other spiders and invertebrates to fuel their bulbous bellies. Bites typically only occur if trapped against skin and are rare.

Bite Symptoms

Though uncommon, the venomous bite of a hobo spider can be medically significant. At first there may be mild stinging pain. After several hours, a blister surrounded by a red, swollen area may form.

In severe cases, the bite site can develop into an open sore. Other possible symptoms include headache, nausea and fatigue. Seek medical care if bite reactions seem serious or persist beyond a few days.

Wolf Spider

Wolf spiders comprise a large family of hairy spiders with robust bodies. One species in the US with a notably prominent behind is the Carolina wolf spider.

This spider has a brown or grey hairy body reaching up to 1 inch long. The sizable oval abdomen takes up much of the body mass, especially after a meal.

Distinctive Features

In addition to its plump rump, the Carolina wolf spider has these telling traits:

• Brown/grey color with stripe pattern on body
• Mottled pattern on the large abdomen
• Sturdy, hairy legs and palps
• Eyes arranged in three rows

Habits and Behavior

Carolina wolf spiders prowl open areas like lawns, pastures, fields and gardens during the night. They hide out during the day in burrows, under rocks and downed logs. Despite their intimidating size, they are not aggressive.

These hunters use their large front legs and excellent eyesight to catch a variety of insects, spiders and other small prey. Their venom only poses mild risk to humans.

Bite Risk and Symptoms

Bites are uncommon and rarely cause significant reactions. Mild redness, swelling and itching may occur at the bite site. Usually the symptoms subside without issue in a couple days.

Wolf spider bites are typically less severe than some other spiders due to their weaker venom and reluctance to bite humans. They only pose risk if repeatedly provoked.

Nursery Web Spider

The nursery web spider is a gardener's friend that can sometimes wander indoors. This spider has a brown oval body reaching around 34 inch long supported by dense hair.

The abdomen is large and rounded, especially after feeding at night. The legs span about 2 inches tip to tip, making them seem even bigger.

Identification Tips

Other ways to identify the nursery web spider include:

• Pale brown or tan color with markings
• Long, dense hairs cover the body
• Prominent spinnerets at the rear
• Long legs with black and white bands

Habitat and Behavior

As their name suggests, nursery web spiders build large web nests in shrubs and vegetation. The female guards her egg sac in the center of the web. They are common yard spiders but may wander inside occasionally.

Though they look intimidating, nursery web spiders are not aggressive. They use their size and speedy legs to capture caterpillars, beetles, mosquitoes and other prey at night.

Bite Risks

The nursery web spider rarely bites, and most bites produce only mild effects like temporary pain and redness. Severe reactions are unlikely but seek medical care if bite symptoms seem serious.

Fishing Spider

Fishing spiders belong to the Dolomedes genus and frequent water edges. They have robust, hairy brown bodies and long legs for skimming along the waters surface.

Their oversized abdomens give fishing spiders a big-bottomed look. The abdomen expands considerably after eating to hold their aqueous prey.

Identification Features

In addition to the large abdomen, fishing spiders have these key traits:

• Brown color with chevron markings
• Less dense hairs than wolf spiders
• Long legs with dark bands
• Front legs noticeably thicker than hind legs

Habits and Habitat

These aptly named spiders dwell along the edges of ponds, marshes and slow streams. They don't build webs, instead patrolling the water's surface to hunt insects, small fish and tadpoles.

Fishing spiders may wander into homes and garages near water. Despite their imposing size, they are not aggressive to humans.

Bite Risks

While uncommon, fishing spider bites contain venom that can cause mild reactions. Redness, swelling, pain and itching around the bite site may occur. The symptoms are rarely medically significant.

Preventing and Controlling Spider Infestations

While most big-bottomed brown spiders pose minimal risks, their large size and appearance can be unsettling. Take these steps to deter spiders from taking up residence in and around your home:

• Seal cracks and openings to prevent access
• Clean up clutter like piles of wood, debris and vegetation
• Install lighting around doors and yard areas to deter nocturnal species
• Vacuum regularly to remove cobwebs and egg sacs
• Use pest deterrents like diatomaceous earth in infested areas

If you need to remove a large spider, trap it under a cup and slide paper underneath to safely relocate it outside. Avoid smashing spiders as this releases pheromones that attract more!

When to Seek Medical Care

Most brown spider bites cause only minor effects, if any. Seek prompt medical attention for bites if you experience:

• Severe pain that persists more than 6-8 hours
• Nausea, fever or spreading redness/swelling
• Possible infection like pus, oozing or foul odor
• Skin ulcers or dead tissue at the bite site
• Muscle cramps, weakness or tremors
• Difficulty breathing or altered mental state

Notify your doctor of any concerning reactions so they can provide appropriate treatment and monitoring if needed.

Conclusion

Some spiders roaming around backyards and homes have noticeably large, round abdomens. Brown spiders like the brown recluse, hobo, wolf, nursery web and fishing spiders all sport a big butt, especially after feeding.

While their appearance may seem creepy, most of these spiders pose minimal risks to humans. Their venom usually causes only mild, temporary reactions treatable at home. With proper identification and basic prevention measures, most brown spiders with big butts are more nuisance than threat.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.