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Ordgarius magnificus (Family Araneidae)

Magnificent Spider

Distribution

Distribution:

Forest habitats in eastern New South Wales and southern Queenland (QLD, NSW).

Features:

Female Magnificent Spiders are large, squat spiders (10 to14 mm body length and almost as wide), creamy-white in colour with a delicate pattern of pink and yellow spots on the abdomen, and a "crown" of white and reddish tubercles on the head. Males are tiny (1 to 2 mm body length). There are 3 species of bolas spiders, Ordgarius species, in Australia, all of which specialise in catching moths with their unique, single line, "bolas" webs. . They are descended from orb-web weaving ancestors and their simple web represents the highly modified remnant of an orb web.

Ecology/Way of Life:

These Magnificent Spiders are not often seen, as they are only active at night, have a very simple, temporary web and live in trees or tall shrubs, rarely less than some 2 metres or more above the ground. However, they are just as likely to be seen one in a well-vegetated suburban backyard as in the bush during summer and autumn. Their presence is usually indicated by a cluster of large, brown egg sacs hanging among foliage. The spider will be found nearby, sheltering by day in a thimble-shaped silk and leaf retreat.

At night, the female spins a trapeze line from twigs above an open space in the branch or foliage. She hangs from this trapeze and spins into the space a short, single line of silk with a large droplet of very sticky silk, the bolas, at its end; sometimes there may be a few smaller droplets above. This hanging silk line is the equivalent of the sticky spiral silk of the orb web. The upper end of the line is held by the female's second leg. As she hangs there, the spider emits an airborne chemical (pheromone) which is attractive to male moths of the family Noctuidae - because the scent is very similar to that used by female noctuid moths to attract males (an example of aggressive mimicry). Vibration sensitive hairs on the spider's outstretched legs can sense the wing beats of an approaching moth. Once this occurs, the spider begins to swing the bolas around in a circle beneath her. The moth comes closer and closer until it is hit by the sticky bolas, and then it flutters in tethered flight while the spider hauls it in. The hapless moth is then bitten, wrapped and either eaten or hung up for a later feast. Several moths may be caught in a night.

The Magnificent Spider makes spectacular egg sacs, both in size and numbers, from late summer to early winter. The light brown, spindle-shaped egg sacs are conspicuous, being up to 5 cm long and quite conspicuous - many are targeted by flies and wasps that parasitise spiders' eggs. Up to 9 sacs may be made by a spider in a season, each with several hundred eggs. Amazingly, the tiny male spiders mature within the egg sac, emerging with fully functional mating organs. Female spiderlings don't mature until much later. This time difference probably ensures that brother and sister spiderlings do not interbreed, but it is not clear quite why the time difference is so large.

Preferred Image

Interaction with Humans/Threats:

No interactions or threats have been recorded.

Other Comments:

Ordgarius magnificus was described by Rainbow. The origin of the genus name has yet to be determined; the species name is from the Latin word, magnificus = splendid.

Further Reading:

For further photographs of eggcases and other information, see: http://www-personal.une.edu.au/~dbritton/orgmag.htm

Longman, H.A. (1922). The magnificent spider: Dicrostichus magnificus Rainbow: Notes on cocoon spinning and methods of catching prey. Proceedings of the Royal Society of Queensland 33: 91-98

McKeown, K. (1963). Australian Spiders. Angus and Robertson, Sydney.

Stowe, M.K. (1986). Prey specialisation in the Araneidae. In W.A. Shear (ed.), Spiders: Webs, Behaviour and Evolution. Stanford University Press.

Topics:

Parasitism Silk Spider webs Pheromones Sexual dimorphism Mimicry

Acknowledgments:

Text & map by Mike Gray; photographs by Mike Gray, courtesy of the Australian Museum

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Please Contact ABRS if you wish to discuss sponsoring this or other pages.


Images and Multi-media:  
Attached Image  
image/jpeg 13813 bytes Ordgarius furcatus with bolas line
Attached Image  
image/jpeg 56412 bytes Ordgarius magnificus with eggs sacs
Attached Image  
image/jpeg 51843 bytes Ordgarius magnificus
Distribution Map  
image/jpeg 23601 bytes Ordgarius magnificus map

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