150.JPGArgiope Argentata

Silver Argiope Spider


Other common names include Silver Garden Spider, Silver Garden Orb Weaver

Kingdom: Animalia
Phyllum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Araneidae
Genus: Argiope
Species: Argiope Argentata [8]


Range and Abundance: It is generally found in grassy areas in tropical regions of the Americas. It is also found on some of the Galapagos Islands. [1] It's range is basically from the US Southern and Gulf States to Central Argentina. [2]

Coloration and Morphology:The Silver argiope is a large silver species with a predominantly silver and yellow and orange pattern on the dorsal side of the opisthosoma. The opisthosoma has 6 protuberances of different sizes that extend sideways and are distinctly different from the rest of the body.149.JPGThese protuberances allow this species to be relatively easily distinguished from other members of the Argiope genus. [1]
both.jpg
male and female











Males are much smaller than females and mature at the sixth or
seventh instar, whereas females mature at the 13, 14, or
15 instar. [1]






155.JPG
Silver Argiope web in low herbage

Habitat : The habitat of the Silver Argiope is generally in shrubs, gardens, forest, prickly pear plants. [2]
They are also found in clearings, grassland edges and at the margins of roads and trails, or wherever there is low herbage and shrubs. They are found low to the ground generally.
[5]

Ecology : The web is almost always inclined at 5 - 20 degrees from the vertical. The spider hangs on the underside of the web. Activity is diurnal.[1]

Silver Argiope spiders generally have the same predators as most other spiders and insects in the tropical rainforest, such as birds, larger spiders, and lizards. Salticids, or jumping spiders, evoke predator-avoidance reponses, such as stilting (straightening all four legs to make itself appear larger than it is). [7] Attacks by hummingbirds were observed to cause the spider to drop egg masses and retreat. In generaly, birds pose the most threat to the Silver Argiope, as they have the easiest access to the spider.
[6]

Behavior: These spiders produce webs that generally have web decorations, or stabilimenta, made of only silk. Smaller spiders mainly produce discoid decoration whereas large spiders construct at least part of a cruciate decoration or none at all. Barrier webs are predominant among smaller spiders and are generally rarely there for larger spiders. Spiders in the genus Argiope produce zig zag bands of wrapping silk. [1]


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Discoid
458.JPG
Cruciate











The function of these web decorations are not exactly known, but may be for prey attraction, predator protection, and web advertisement to avoid accidental web damage. The stabilization explanation seems very unlikely. [1]

Barrier webs are irregular tangles of non-sticky threads on one or both sides of the orb web, and may either support the web or protect the spider from predators by creating a mechanical barrier. [1]

The spider sits at the center of the web with legs extended two by two in a cruciate manner. [1]

Orb weaving spiders spin a total of seven different kinds of silk. [4] Argiope argentata tear down their web every two days to weave a new one, but the barrier web remains unless the spider changes location.
[4]


Diet : Silver argiope spiders eat insects, such as moths, butterflies, and stingless bees, Orthoptera (grasshoppers,[[image:file/view/115.JPG width="221" height="167" align="right" caption="wrapping a"]] crickets, locusts), Odonata (dragonflies, damselflies), Hemiptera (cicadas, aphids, planthoppers, shield bugs), Lepidoptera (butterflies), Diptera (mosquitos, gnats, flies), Coleoptera (beetles), Dictyoptera (cockroaches, termites, Phasmatodea(praying mantis). Argiope argentata bites moths and butterflies that strike its web, but simply restrains other smaller insects by wrapping them in silk. [3]

Other species that interact with your species : The webs of the silver argiope spider are sometimes occupied by the commensal Dewdrop spider, Argyrodes. Dewdrop spiders, often called kleptoparisites, are smaller than the female Argiope argentata and will take food out the the web or eat food the host spider does not eat. It generally does not attack Silver argiope spiders because of the size difference. [3]

Some possible predators include:
Coccyzus melacoryphus (Dark-billed cuckoo)
Myiarchus magnirostris (Large-billed Flycatcher)
Nesomimus parvulus (Galapagos Mockingbird)
Dendroica petechia (Yellow Warbler)
Geospiza scandens (Cactus Finch)
Chamarynchus parvulus (Small tree-Finch)
Certhidea olivacea (Warbler Finch)
Tropidurus sp. (a type of lizard) [4]



Personal interactions: The Silver Argiope spider stayed in one location for about two days, which is consistent with the literature that says they tear down their webs every two days. The spider was also found in many sizes with webs in different stages. The smaller spiders did produce the discoid web stabilimenta. The larger spiders, however, produced both the discoid and the cruciate shape on their web, so it was difficult from my personal interactions to state whether or not there is really a size correlation with the design of stabilimenta.

I also observed that when I approached the spider and got close enough that I made vibrations on the web (with my breath, touching the plant, touching the web itself), the larger spiders stilted themselves. The smaller spiders ran to the underside of their web when I got close within inches of their web.

I managed to find four different Silver Argiope spiders in the La Selva Rainforest at the OTS Biological Station, three of which were right around the laboratories. These spiders generally do not need deep forest to make their web in, suggesting they like some sunlight and more open areas. None were found in dense parts of the rainforest.


Works Cited:
1. Uhl, G (2008) Size dependent occurrence of different types of web decorations and a barrier web in the tropical spider Argiope argentata (Fabricius 1775) (Araneae Araneidae). Tropical Zoology 21: 97-108.

2. http://greennature.com/gallery/spider-pictures/spider_spinnerets.html


3. Trail, D. S. (1980) Predation by Argyrodes (Theridiidae) on solitary and communal spiders. Psyche 87: 349-356.

4. Blackledge, T. A. (2006) Silken toolkits: biomechanics of silk fibers spun by the orb web spider Argiope argentata (Fabricius 1775). The Journal of Experimental Biology 209: 2452-2461.

5. Robinson, M. H. (1969) Predatory behavior of Argiope argentata (Fibricius). American Zoologist, Vol. 9, No. 1: 161-173.

6. Hoffmaster, D. K. (1982) Predator avoidance behaviors of five species of Panamanian orb-weaving spiders( Araneae; Araneidae, Uloboridae). J . Arachnol.,1 0:69-73.
6. Hoffmaster, D. K. (1982) Predator avoidance behaviors of five species of Panamanian orb-weaving spiders( Araneae; Araneidae, Uloboridae). J . Arachnol.,1 0:69-73.

7. W. W. Tolbert. (1975) Predator Avoidance Behavior and Web Defensive Structures in the Orb Weavers, Argiope aurantia and Argiope trifasciata (Araneae, Araneidae). Psyche 82:29-52, 1975.


8. Encylopedia of Life. Argiope Argentata (Fabricius, 1775). 3-26-10. 4-21-10. http://www.eol.org/pages/1194665