Genus: Nephila (golden orb-web spiders)

Life > Eukaryotes > Opisthokonta > Metazoa (animals) > Bilateria > Ecdysozoa > Panarthropoda > Tritocerebra > Arthropoda > Arachnomorpha > Cheliceriformes > Chelicerata > Euchelicerata > Arachnida > Araneae > Araneomorpha > Family: Nephilidae

There are 15 Nephila species known globally, four of which occur in southern Africa. Nephila komaci, which occurs in southern Africa, is the largest known web-spinning spider, and members of Nephila make the largest orb webs - in fact large enough and strong enough to accidentally catch small birds.

Description

The largest and most impressive genus in the Nephilidae is Nephila. Females are large, measuring 15 - 40 mm in length, with a leg span of 100 - 120 mm, while the male is only about 5 - 9 mm, with leg span of up to 25 mm, and it is only about one thousandth of the female's weight. Nephila komaci, found in Tembe Elephant Park in South Africa and Madagascar, is the largest orb-web spider known.

Distribution and habitat

These spiders occur in warm regions of the world, mainly tropical and subtropical areas.

Species native to southern Africa

Four species are currently described from southern Africa; pending a revision further species may be described.

Nephila fenestrata (Black-legged nephila)

Nephila senegalensis (Banded-legged nephila)

Nephila inaurata (Red-legged Nephila)

Nephila komaci (Komacís Nephila)

 

Prey capture

A large vertical, sulphurous yellow orb-web is constructed, which has the top section missing in adult webs. Juvenile spiders construct complete orb webs. In semi-social populations, their webs are joined together forming an awesome, almost impenetrable curtain of webs - like something from an Indiana Jones movie (). These webs are supported by knock down strands of silk in front of and behind the orb-web. The web is usually supported between two trees and can span enormous spaces even across highways with the orb up to a meter wide, about 1.5 meters or more from the ground and is capable of capturing small birds (see photo below). There is no evidence that these birds are eaten but they may be cut out of the web by the spider. Unlike most orb-webs, nephilid webs are partially repaired and not replaced. Most of the activity is conducted by day (diurnal).

Side-on view of Nephila fenestrata web showing the knock-down strands of silk in front and behind the main web. Also note how the top section of the web is missing, a characteristic of webs made by adult Nephila. [photo Norman Larsen ©]

Mating and reproduction

The Nephila male copulates with the female while she is preoccupied with feeding. The males of some Nephila species, once mated, will break off parts of their palps, sealing the femaleís genital openings. The female Nephila constructs her egg sac on a leaf or tree bark; there are about 400 - 1500 eggs per sac.

There are usually one or two amorous males in the female's web as well as

Juveniles are very variable and can be confused with other species as the legs can be indistinctly banded.
The generic name Nephila is derived from Greek, "nen" meaning "to spin" and "philos" meaning "love" thus meaning "fond of spinning".

Ecological interactions

Commensal species

There are often one or more tiny spiders with silver triangular abdomens on Nephila webs. These are called dewdrop spiders of the genus Argyrodes (family Theridiidae) and they clean the orb-webs of prey too small for the host spider.

Predators

Nephila spiders are eaten by:

  • Cercopithecus pygerythrus (Vervet monkey). Quote from South African National Survey of Arachnida (SANSA) Newsletter 11 & 12 (2010) (editors A. Dippenaar-Schoeman and C. Haddad). "Elsa van Niekerk, the graphic artist at ARC-PPRI, is involved in the rehabilitation of wild animals and she has observed some very interesting behaviour of her vervet monkeys. They love feeding on large golden orb-web spiders. The spiders are grabbed out of the web (sometimes two monkeys join forces to pull it off successfully) and the spider is immediately put in their mouths with the legs sticking out. The older individuals train the younger ones how to do it. She has now also seen how they steal insects out of the orb-webs. If this is a general behaviour they might have an effect on golden orb-web spider numbers in areas."

Parasitoids

  • Hymenoptera > Encyrtidae
    • Amira durantae wasps parasitize Nephila eggs sacs, with a specific record for Nephila inaurata (Prinsloo 1983).

Birds caught in webs

The webs of Nephila species are so large and strong that they occasionally trap flying birds. There is no evidence that the spiders eat the birds. In southern Africa, there are the following records of birds trapped by Nephila spiders (information mainly from Brooks, 2012):

Brooks (2012) mentions a number of other birds from southern Africa that have been caught in spider webs but the genus of spider is not specified.

 
Immature Barn swallow caught in a Nephila web, Greater Umbabat Nature Reserve, South Africa. [photo Johann Grobbelaar ©]  

Links

Publications (by date)

  • Webber JI. 1974. Blue waxbill caught in a spider's web. Ostrich 45: 262.
  • Vernon C. 1976. Red-faced crombec caught in a spider's web. Honeyguide 85: 41.
  • Prinsloo GL. 1983. A parasitoid-host index of Afrotropical Encyrtidae (Hymenoptera: Chalcidoidea). Entomology Memoir of the Department of Agriculture Republic of South Africa 60: 1-35. pdf
  • Kuntner M, Levi HW. 2006. Nephila hirta, a new synonym of Eustala fuscovittata (Araneae, Araneidae). Journal of Arachnology 34: 444-447.
  • Kuntner M, Agnarsson I, Gregorič M. 2009. Spider eunuch phenomenon induced by female or rival male aggressiveness. Journal of Arachnology 37(3): 266-271. doi: 10.1636/St08-67.1
  • Brooks DM. 2012. Birds caught in spider webs: a synthesis of patterns. The Wilson Journal of Ornithology 124(2): 345-353. doi:  10.1676/11-148.1

 

Text by Norman Larsen ©


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