How to Identify Common Cellar Spider Species

Cellar spiders are among the most fascinating and often misunderstood arachnids found in homes and damp, dark places like basements, garages, and cellars. Known for their long, spindly legs and delicate webs, these spiders play an essential role in controlling insect populations. However, identifying cellar spider species can be tricky due to their subtle differences and overlapping physical features. This article will guide you through the characteristics, habitats, and behaviors of the most common cellar spider species to help you accurately identify them.

What Are Cellar Spiders?

Cellar spiders belong primarily to the family Pholcidae, a group of araneomorph spiders known for their long legs relative to their body size. They are sometimes colloquially referred to as “daddy long-legs,” though this name is shared with other unrelated species such as harvestmen and crane flies.

Typically, cellar spiders feature:

• Small bodies ranging from 2 to 10 millimeters.
• Extremely long, thin legs often several times the length of their body.
• Pale coloration that blends well with indoor environments.
• Irregular cobweb-like webs that hang in corners and crevices.

Their presence is generally harmless to humans. They are not aggressive and rarely bite. Instead, they prey on small insects and other spiders, contributing to household pest control.

Key Traits to Look For When Identifying Cellar Spiders

When trying to identify a cellar spider species, consider these key physical and behavioral traits:

1. Body Size and Shape
   Most cellar spiders have a small, oval-shaped body that can be translucent or pale brown. Some species have more rounded abdomens while others have elongated ones.

2. Leg Length and Thickness
   The length of the legs compared to the body is a defining characteristic. Some species have extremely thin legs that appear fragile; others have thicker or banded legs.

3. Color Patterns
   While many cellar spiders are uniformly pale or beige, some display subtle markings such as stripes or spots on their abdomen or cephalothorax.

4. Eye Arrangement
   Pholcid spiders typically have six or eight eyes arranged in two groups. The pattern can help distinguish species.

5. Web Structure
   Cellar spiders spin messy, irregular webs often placed in corners or along ceilings. The complexity and placement of the web may vary by species.

6. Habitat Preferences
   Although all cellar spiders favor dark, moist areas like basements and cellars, some species prefer specific microhabitats such as outdoor rock crevices or caves.

Common Cellar Spider Species

Below are some of the most commonly encountered cellar spider species with detailed descriptions to aid identification:

1. Pholcus phalangioides (Common Cellar Spider)

Description:
Pholcus phalangioides is perhaps the best-known cellar spider worldwide. It has a small grayish-white body about 7–8 mm long with extremely long legs that can reach up to 50 mm or more. The legs are usually pale with occasional faint banding.

Distinctive Features:
– Oval-shaped abdomen with no distinct markings.
– Eight eyes arranged in two groups of three on each side plus two centrally located.
– Very thin, fragile-looking legs.

Habitat:
Common indoors in basements, garages, sheds, and cellars worldwide; also found in caves and under rocks outdoors.

Behavior:
Known for its vibrating behavior when disturbed—rapid shaking of its web to confuse predators.

2. Psilochorus simoni

Description:
Psilochorus simoni resembles Pholcus phalangioides but has a shorter leg-to-body ratio and slightly darker coloration on its cephalothorax (head region).

Distinctive Features:
– Slightly smaller size, usually under 6 mm body length.
– Darker cephalothorax with light brown abdomen showing faint striping.

Habitat:
Mostly found outdoors under rocks or leaf litter but occasionally indoors in damp storage areas.

3. Artema atlanta

Description:
Artema atlanta is a large pholcid spider often mistaken for Pholcus phalangioides but with distinct coloration and markings.

Distinctive Features:
– Larger body size up to 10 mm length.
– Abdomen marked with grayish-brown patterns or blotches rather than plain coloration.

Habitat:
Typically found in warmer climates indoors around windowsills or on walls in shaded locations.

4. Crossopriza lyoni

Description:
Crossopriza lyoni is recognizable by its unusual leg posture and distinctive dark stripes running along its body.

Distinctive Features:
– Long legs with noticeable dark bands near joints.
– Abdomen has longitudinal stripes that contrast with lighter background color.

Habitat:
Common in tropical regions indoors under furniture or in corners of rooms.

5. Modisimus species

Description:
This genus includes several cellar spider species that are smaller than Pholcus phalangioides with shorter legs relative to body size.

Distinctive Features:
– Compact bodies with brownish or tan coloration.
– Legs less elongated compared to other pholcids; sometimes club-shaped tips on legs are noticeable.

Habitat:
Found mostly outdoors in leaf litter or caves but occasionally enter human structures.

How to Differentiate Cellar Spiders from Similar Arachnids

Cellar spiders can be confused with other arachnids like harvestmen (Opiliones) or daddy longlegs crane flies (Tipulidae), which are not true spiders.

Differences From Harvestmen

| Feature | Cellar Spiders | Harvestmen |
|——————|———————————–|——————————–|
| Body Segmentation | Distinct cephalothorax & abdomen | Fused single rounded body |
| Legs | Long but jointed clearly | Very long very thin legs |
| Web Production | Builds messy webs | Do not build webs |
| Number of Eyes | Usually 6 or 8 | Two eyes only |

Differences From Daddy Longlegs Crane Flies

Crane flies resemble giant mosquitoes rather than spiders — they have wings and only six legs (insects), whereas cellar spiders have eight legs (arachnids).

Tips for Safely Observing and Identifying Cellar Spiders

If you want to observe cellar spiders closely for identification:

• Use a magnifying glass or macro lens on your smartphone camera.
• Capture spiders gently using a clear container if necessary.
• Avoid direct handling as it may harm the spider.
• Photograph multiple angles including leg arrangement, eye pattern, and abdomen markings.
• Note the exact location where you found them (indoor/outdoor) since habitat is important for identification.
• Consult local arachnid field guides or online databases such as BugGuide.net for comparison photos and verification.

Why Identifying Cellar Spiders Matters

Understanding which cellar spider species inhabit your home can:

• Help dispel fears about dangerous bites (most household cellar spiders are harmless).
• Inform pest control decisions—cellar spiders prey on nuisance insects like mosquitoes and flies.
• Contribute to local biodiversity knowledge if you report sightings to citizen science projects.
• Encourage appreciation for arachnid diversity instead of indiscriminate killing.

Conclusion

Identifying common cellar spider species requires attention to details such as body size, leg length, coloration patterns, eye arrangement, and habitat preferences. While Pholcus phalangioides remains the most widespread indoor species globally, other genera like Psilochorus, Crossopriza, Artema, and Modisimus broaden the diversity of cellar spiders you may encounter depending on your geographic location.

With patience and careful observation supplemented by good reference materials, anyone can develop the skill to recognize these gentle arachnid allies lurking quietly in our cellars and corners—natural pest controllers deserving respect rather than fear.