Yellow garden spider

Order: Araneae
Family: Araneidae
Genus and species: Argiope aurantia Lucas

This is a brightly colored and conspicuous species frequently observed in open, sunny areas, especially in late summer and early fall. Female yellow garden spiders can reach a length of one inch or more. The carapace is silvery-white, and the oval, yellow and black abdomen bears of pair of humps near the base. Males are much smaller, rarely reaching much over a quarter of an inch long.

This species occurs in Nova Scotia and southern Ontario, the eastern half of the United States, and south to Guatemala. It also occurs in California and Oregon. It is absent from intervening arid areas. Females build large webs, up to two feet in diameter, in open areas among tall grasses and weeds, often in wet or marshy areas. They are also familiar sites around homes, in flower and vegetable gardens, in old fields, and in similar habitats (Levi 1968; Kaston 1981).

The web consists of dry spokes supporting a spiral thread of adhesive silk. The hub is separated from the spirals by a free zone. The spiders rest head down day and night at the hub of the web over a conspicuous zigzag band of bright white noncapture silk known as a stabilimentum. The stabilimentum apparently affords protection, perhaps by camouflaging the spiders, startling predators, or acting as an aposematic warning of the presence of webs. It seems to be especially effective in preventing birds from flying through webs. However, it can also cost spiders the loss of prey, and hungry spiders, which most need to capture prey, are less likely to build stabilimenta (Blackledge 1998; Blackledge and Wenzel 1999). The female usually eats her web each day and constructs a new one, often in the same place (Reed et al. 1969). Females can handle prey much larger than themselves, including grasshoppers, katydids, cicadas, June beetles, moths, wasps, bees, and other insects (Fitch 1963). In east Texas cotton fields, major prey items are aphids, flies, grasshoppers, and ants and bees (Nyffeler et al. 1987).

Spiders reach maturity in summer. Although males build webs, after they reach maturity they wander in search of females, and they can be found in the females’ webs. Light brown, oval or spherical egg sacs up to an inch long are produced in late summer or early fall. Each sac contains up to a thousand or more eggs. Spiderlings winter over inside the sacs, and they disperse in the spring. Mortality due to predators and parasites can be very high (Lockley and Young 1993). In the spring, the young spiders build small webs in low vegetation. As they grow, they tend to build larger and more conspicuous webs higher in vegetation.

These spiders are not particularly dangerous to people, and their bites result in nothing more than a sore, itchy swelling that goes away in a few days. The medical literature contains at least one report of a bite by A. aurantia (Gorham and Rheney 1968). Mild pain some distance from the site of the bite was suggestive of a neurotoxin.

References:

Blackledge, T. A. 1998. Stabilimentum variation and foraging success in Argiope aurantia and Argiope trifasciata (Araneae: Araneidae). Journal of Zoology 246: 21-27.

Blackledge, T. A., and J. W. Wenzel. 1999. Do stabilimenta in orb webs attract prey or defend spiders? Behavioral Ecology 10 (4): 372-376.

Fitch, H. S. 1963. Spiders of the University of Kansas Natural History Reservation and Rockefeller Experimental Tract. University of Kansas Museum of Natural History, Lawrence. 202 pages.

Gorham, J. R. and T. B. Rheney. 1968. Envenomation by the spiders Chiracanthium inclusum and Agriope aurantia. JAMA 206 (9): 1958-1962.

Kaston, B. J. 1981. Spiders of Connecticut. State Geological and Natural History Survey of Connecticut, Department of Environmental Protection Bulletin 70: 1020 pages.

Levi, H. W. 1968. The spider genera Gea and Argiope in America (Araneae: Araneidae). Bulletin of the Museum of Comparative Zoology 136 (9): 319-352.

Lockley, T. C., and O. P. Young. 1993. Survivability of overwintering Argiopeaurantia (Araneidae) egg cases, with an annotated list of associated arthropods. Journal of Arachnology 21: 50-54.

Nyffeler, M., D. A. Dean, and W. L. Sterling. 1987. Feeding ecology of the orb-weaving spider Argiope aurantia (Araneae: Araneidae) in a cotton agroecosystem. Entomophaga 32 (4): 367-375.

Reed, C. F., P. N. Witt, and M. B. Scarboro. 1969. The orb web during the life of Argiope aurantia (Lucas). Developmental Psychobiology 2 (2): 120-129.

Links:
• University of Michigan Museum of Zoology
• San Diego Natural History Museum