The orb-weaver Nuctenea umbratica

A beautiful, dark brown spider of medium size with a delicate, sand-coloured pattern. This is Nuctenea umbratica.

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Due to its nocturnal nature, the walnut orbweaver Nuctenea umbratica is sadly rarely seen out of its retreat throughout the day. Despite its tendency to live in the shadows, this spider is actually quite beautiful.

In German, people refer to it as “Spaltenkreuzspinne”, translated to “crevice cross spider”, as it likes to hide in crevices during the day. However, this German name has its pitfalls, because Nuctenea umbratica does not belong to the genus of cross spiders Araneus.

A striking feature is its flat opisthosoma (abdomen), that helps the spider to hide in the smallest crevices in walls or other man-made constructions.

The very first record of this spider goes back to the Book “Histories Animalium Angliae tres tractatus” written in Latin by British Naturalist Martin Lister. He described this spider to be blackish in colour with a figure of an oak leaf drawn upon its abdomen.

This leaf-like marking is often referred to as the “folium” among arachnologists. Two lighter moon-shaped markings are also visible on the ventral side of the opisthosoma, like shown in the picture above.

Habitat and Webbing

Originally known to hide under bark, Nuctenea umbratica is now increasingly found close to humans (arages, 2024). These spiders prefer old places undisturbed by human activity, such as older wooden fences or stone walls.

Personally, I have observed these spiders a lot on road signs with good hiding places, as the following pictures show.

Nuctenea umbratica often spends its day hidding in a cravice near its web. The construction of its web happens after nightfall with a signal thread being laid from the center to its hiding place. Only at night does it leave its hiding place and sit in the center of its web (Levi, 1974).

This orb-weaver relies on size, its web can reach a diameter of up to 70 cm (Levi, 1974). The large spacing of the threads makes the net appear extremely rather flimsy in the wind (F. Martini & J. Goeze, 1778).

It has also been observed how Nuctenea umbratica uses self-generated oscillations to determine whether an insect is caught in its web (W. Piel, 1985).

Sexual dimorphism, mating behaviour & offspring

Sexual dimorphism. Colour and pattern do not differ greatly between the sexes, but in males the folium appears to be more pronounced than in females (Levi, 1974). In addition, males can be differentiated from females by the shape of their pedipalps.

Adult spiders of different sexes also differ in their body length. Adult males measure around 0.9 mm in body length, while females can reach a length of up to 16.0 mm (araneae, 2024).

As this spider is mainly nocturnal, the naturalist M. Lister noted as early as 1687 that this spider appears to mate at night within the female’s web (F. Martini & J. Goeze, 1778). It is also known that the males use each of their palpi multiple times for mating without any further problems (Levi, 1974).

Observations of 2024

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Observations of 2025

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Sources

• Images – All images were taken by the author N. Schneider.
• arages – Wiki der Arachnologischen Gesellschaft (online). Nuctenea umbratica. Retrieved 10.12.2024 – https://wiki.arages.de/index.php?title=Nuctenea_umbratica
• araneae – Spiders of Europe (online). Nuctenea umbratica. Retrieved 10.12.2024. – https://araneae.nmbe.ch/data/1322
• C. Kropf & H. Frick. (2024). Spider Biology. Lecture UniBe, Switzerland.
• F. H. W. Martini & J. A. E. Goeze (1778). Martin Listers Naturgeschichte der Spinnen überhaupt und der Engelländischen Spinnen insbesonderheit, aus dem Lateinischen übersetzt, und mit Anmerkungen vermehrt. – https://tinyurl.com/5n8z2w6u
• H. W. Levi (1974). The orb-weaver genera Araniella and Nuctenea (Araneae: Araneidae). Bulletin Museum of Comparative Zoology, Vol. 146, No. 6, S. 300-305 – https://wsc.nmbe.ch/reference/4536
• W. Piel (1985). A Note on the ‘Bouncing-Effect’ in Orb- and Funnel-Weavers. Notes on Nuctenea umbratica by Spider and Harvestman Recording Scheme website – https://srs.britishspiders.org.uk/portal.php/p/Notes+on/s/Nuctenea%20umbratica