Walnut Orb-weaver, Flat-bellied Orb-weaver
Nuctenea umbratica
Araneidae (Orb-Weavers), Order Araneae
Physical Description
A notably flattened spider with a wide, dorso-ventrally compressed abdomen and cephalothorax, specifically adapted for hiding in narrow crevices. The cuticle appears leathery and somewhat glossy.
Size Estimate
Females typically 11-16mm body length; males 7-10mm. Leg span can reach up to 30-35mm.
Coloration & Markings
Dark mahogany to chocolate brown or nearly black. The abdomen features a distinct dark, oak-leaf-shaped folium pattern outlined in a lighter cream or yellowish color. There are two visible pits (sigilla) on the dorsal surface.
Web Type
Large, vertical, slightly irregular orb web. During the day, the spider hides in a nearby crack, connected to the web by a signal thread.
Eye Arrangement
Eight eyes in two rows typical of Araneidae; the four median eyes form a central trapezoid, with lateral eyes paired on small tubercles.
Leg Characteristics
Robust, relatively short compared to other orb-weavers, colored with dark and light brown bands. Strong spines are present on the legs for grasping prey.
Venom & Safety Information
Venom Information
Contains neurotoxic proteins designed for paralyzing small insects; however, it is not potent or dangerous to humans.
Medical Significance
Low medical significance. Bites are rare and generally occur only if the spider is pressed against the skin. Symptoms are comparable to a mild wasp sting (localized pain and swelling).
Safety Recommendations
Harmless to humans. If found indoors, it can be safely relocated outside using a jar and a piece of paper. No special precautions are necessary.
Habitat & Behavior
Habitat & Range
Widespread across Europe, parts of North Africa, and Western Asia. Frequently found on wooden fences, under loose bark, and in the eaves of buildings.
Behavior & Temperament
Nocturnal and highly secretive. It remains in its retreat during the day and emerges at dusk to sit at the center of the web. It is non-aggressive and will retract its legs into a 'frozen' ball if threatened.
Diet & Prey
Generalist predator of flying insects including moths, flies, and beetles. It uses its heavy body to quickly overwhelm entangled prey.
Seasonal Activity
Vividly active from late spring through autumn, with peak mating activity in late summer.
Description
The Walnut Orb-weaver is a master of camouflage, masquerading as a piece of bark or a dark knot in wood. Its flattened shape allows it to disappear into gaps only a few millimeters wide.
Key Features
Significantly flattened profile, dark glossy brown color, and the oak-leaf-shaped folium mark on the abdomen.
Similar Species
Larinioides sclopetarius (Bridge Spider) and Larinioides ixobolus, though Nuctenea is much flatter and darker.
Life Cycle
Females produce yellowish-white silk egg sacs hidden in crevices. Spiderlings emerge in spring. Adults can live up to 2 years, often overwintering in deep cracks.
Ecological Importance
Serves as an important natural pest controller near human dwellings, consuming large numbers of nocturnal nuisance insects.
Conservation Status
Not evaluated by IUCN, but considered common and stable throughout its range.
Interesting Facts
Its flat shape is an evolutionary adaptation for 'crevice-dwelling,' allowing it to survive in environments where rounder spiders would be vulnerable to birds.
Photography Tips
Focus on the dorsal folium pattern. Use a flash or side-lighting to reveal its flattened texture against a wall or bark.
Identified: 2026-07-02T02:03:27.825928