How to Identify a False Widow Spider: A Comprehensive Guide
False widow spiders (Steatoda species) are often mistaken for their more notorious cousins, the black widows. While they share some similarities, false widows are generally less venomous and their bites are rarely medically significant. However, it’s still important to be able to identify them correctly to avoid unnecessary fear and ensure appropriate action, should you encounter one. This comprehensive guide will provide you with detailed steps and instructions on how to confidently identify a false widow spider.
## Understanding False Widow Spiders
Before diving into the identification process, it’s crucial to understand what false widow spiders are and where they fit in the arachnid world.
* **Genus Steatoda:** False widow spiders belong to the genus *Steatoda*, which is part of the Theridiidae family, also known as cobweb spiders or comb-footed spiders. The *Steatoda* genus includes several species commonly found in Europe and North America.
* **Common Species:** The most commonly encountered false widow species include:
* **Noble False Widow (Steatoda nobilis):** This is the species most often associated with the “false widow” name and is the largest and most frequently reported. It originated in the Canary Islands and Madeira but has spread to many parts of the world.
* **Cupboard Spider (Steatoda grossa):** Also known as the dark comb-footed spider, this species is generally darker in color than the noble false widow.
* **Rabbit Hutch Spider (Steatoda bipunctata):** This is a smaller species, often found in sheds and outbuildings.
* **Habitat:** False widow spiders typically build their webs in sheltered locations, such as under window ledges, in sheds, garages, attics, and crevices in walls. They prefer dark, undisturbed areas.
* **Behavior:** These spiders are generally not aggressive and will only bite if they feel threatened. Their venom is less potent than that of a black widow, and most bites result in mild symptoms.
## Step-by-Step Identification Guide
Now, let’s break down the identification process into manageable steps:
**Step 1: Observe the Size and Shape**
* **Size:** False widow spiders are medium-sized, typically ranging from 6 to 12 millimeters in body length for females, and slightly smaller for males. The noble false widow is the largest of the common species, reaching up to 14mm. This is larger than many other common house spiders.
* **Body Shape:** They have a bulbous, globular abdomen that is significantly larger than their cephalothorax (the combined head and thorax). This shape is characteristic of many cobweb spiders.
**Step 2: Examine the Color and Markings**
This is where the identification becomes more nuanced, as coloration and markings can vary between species and even within the same species.
* **Noble False Widow (Steatoda nobilis):**
* **Color:** Typically a dark brown or reddish-brown color. The legs are often a lighter orange-brown.
* **Markings:** The abdomen usually features a distinct pattern of cream or yellowish markings. These markings can vary significantly and may resemble a skull shape in some individuals, particularly juveniles. However, this “skull” marking is not always present or clearly defined.
* **Key Identifying Feature:** Look for a pattern of pale markings on the abdomen against the darker background. The leg color is also a good clue.
* **Cupboard Spider (Steatoda grossa):**
* **Color:** Generally a glossy, dark brown to purplish-black color. They can appear almost black, especially in darker environments.
* **Markings:** Often lacks distinct markings. The abdomen may have faint, indistinct patterns or be uniformly colored.
* **Key Identifying Feature:** The glossy, dark color and lack of prominent markings are distinguishing features.
* **Rabbit Hutch Spider (Steatoda bipunctata):**
* **Color:** Typically a reddish-brown to dark brown color.
* **Markings:** Usually has a line of pale dots running down the center of the abdomen.
* **Key Identifying Feature:** The line of dots on the abdomen is a key identifier.
**Important Note:** Color and markings can be variable, and juvenile spiders may look different from adults. Do not rely solely on markings for identification.
**Step 3: Inspect the Web Structure**
False widow spiders create messy, irregular webs, often described as cobwebs. These webs are typically three-dimensional and lack the organized structure of orb-weaver spider webs.
* **Type of Web:** They build tangled, haphazard webs in sheltered locations.
* **Location:** Look for webs in corners, under furniture, in sheds, garages, and other undisturbed areas.
* **Sticky or Non-Sticky:** The webs are sticky, designed to trap small insects.
**Step 4: Observe the Leg Structure**
While not a primary identifier, the leg structure can provide supporting evidence.
* **Comb-footed Spiders:** *Steatoda* spiders belong to the Theridiidae family, known as comb-footed spiders. This refers to a row of serrated bristles on the tarsus (the last segment) of their hind legs. These bristles are used to comb silk over their prey.
* **Leg Appearance:** The legs are generally slender and may have spines or hairs.
**Step 5: Consider the Habitat**
Knowing where you found the spider can help narrow down the possibilities.
* **Indoor Locations:** Noble false widows and cupboard spiders are commonly found indoors.
* **Outdoor Locations:** Rabbit hutch spiders are more likely to be found in sheds, outbuildings, and gardens.
**Step 6: Use a Magnifying Glass (If Possible)**
If you have access to a magnifying glass, use it to examine the spider more closely. This can help you see the markings and leg structure in greater detail.
**Step 7: Compare with Reliable Images and Descriptions**
Once you have gathered as much information as possible, compare your observations with reliable images and descriptions of false widow spiders. There are many websites and field guides that can help with identification. Be sure to use reputable sources, such as university websites, entomological societies, and trusted pest control companies.
**Step 8: When in Doubt, Consult an Expert**
If you are still unsure about the identification, it is best to consult an expert. You can contact your local university extension office, a pest control professional, or an entomologist. They will be able to examine the spider and provide a definitive identification.
## Distinguishing False Widows from Black Widows
One of the main reasons people want to identify false widow spiders is to distinguish them from the more dangerous black widow spiders. Here’s a comparison:
| Feature | False Widow Spider (Steatoda) | Black Widow Spider (Latrodectus) |
|——————-|————————————————————————————————————————————————————————————————————————————–|—————————————————————————————————————————————————————————————————————————————————————-||
| **Size** | Medium-sized (6-14mm) | Medium-sized (8-13mm), but with significantly longer legs |
| **Color** | Dark brown, reddish-brown, or purplish-black. Markings can vary but are often cream or yellowish. | Glossy black. Females typically have a distinctive red hourglass marking on the underside of their abdomen. |
| **Markings** | Variable markings, may resemble a skull. | Distinctive red hourglass marking on the underside of the abdomen (in females). Males may have red or white markings on their sides. |
| **Shape** | Bulbous abdomen, but more rounded. | Bulbous abdomen that appears more elongated or oval. |
| **Web** | Messy, irregular cobwebs. | Tangled, irregular webs, often with a strong, sheet-like structure near the ground. |
| **Habitat** | Sheltered locations indoors and outdoors, such as under window ledges, in sheds, garages, and attics. | Sheltered locations outdoors, such as woodpiles, sheds, and garages. They prefer dark, undisturbed areas. |
| **Venom Potency** | Less potent than black widow venom. Bites typically result in mild symptoms. | Highly potent neurotoxic venom. Bites can cause severe pain, muscle cramps, nausea, and difficulty breathing. Medical attention is often required. |
| **Behavior** | Generally not aggressive and will only bite if threatened. | Generally reclusive, but females may bite defensively if disturbed or threatened. |
**Key Differences to Remember:**
* **Hourglass Marking:** The red hourglass marking on the underside of the abdomen is the most definitive characteristic of a female black widow spider.
* **Color:** Black widows are typically a glossy black color, while false widows have more variable colors.
* **Venom:** Black widow venom is significantly more potent than false widow venom.
## What to Do If You Find a False Widow Spider
* **Remain Calm:** False widow spiders are generally not aggressive, so there is no need to panic.
* **Observe from a Safe Distance:** Take your time to observe the spider and gather information for identification.
* **Avoid Contact:** Do not attempt to handle the spider.
* **If Bitten:** Clean the bite area with soap and water. Apply a cold compress to reduce swelling. If you experience severe symptoms, such as nausea, muscle cramps, or difficulty breathing, seek medical attention.
* **Control Measures:** If you find a large number of false widow spiders in your home, you may want to consider taking control measures. This could include:
* **Sealing Cracks and Crevices:** Seal any cracks or crevices in your home’s foundation and walls to prevent spiders from entering.
* **Removing Webs:** Regularly remove webs from your home to reduce spider populations.
* **Using Insecticides:** Use insecticides specifically designed for spiders. Follow the manufacturer’s instructions carefully.
* **Professional Pest Control:** Consider hiring a professional pest control company to treat your home.
## Misconceptions About False Widow Spiders
There are many misconceptions surrounding false widow spiders, often fueled by sensationalized media reports.
* **Deadly Venom:** False widow spider venom is not deadly to humans. Bites may cause localized pain, swelling, and redness, but severe reactions are rare.
* **Aggressive Behavior:** False widow spiders are not aggressive and will only bite if they feel threatened.
* **Widespread Infestations:** While false widow spiders are becoming more common in some areas, they are not typically found in large infestations.
## Conclusion
Identifying a false widow spider requires careful observation and attention to detail. By following the steps outlined in this guide, you can confidently distinguish false widows from other spiders, including the more dangerous black widow. Remember to remain calm, observe from a safe distance, and consult an expert if you are unsure about the identification. While false widow spiders can be a nuisance, they are generally not a significant threat to human health.
**Disclaimer:** This guide is intended for informational purposes only and should not be considered a substitute for professional advice. If you have any concerns about spiders or their bites, consult with a medical professional or a pest control expert.