Argiope argentata

Argiope argentata belongs to the genus Argiope. As with all Argiope, there is notable sexual dimorphism in regards to size, with the male being much smaller than the female. The average size of the female A. argentata is 12 millimeters, which is three times the size of the average male. UV-light reflects off of the top surface of their bodies. This UV-reflectance may serve the same purpose as the UV-silk used to spin their webs: to attract pollinating prey by imitating the characteristics of flowers. The under-area of A. argentata has a dark-brown coloring, with a yellow stripe going across it. A. argentata has two sets of eyes: a primary set and a secondary set. ==Habitat and distribution==

Argiope argentata are native to areas of Southern California. It is also found southwards as far as Argentina and Chile. As a spider that is attracted to dry and humid environments, it thrives on the prickly-pear plants of Southern California. This spider is not typically found in Europe, or in places with seasons that involve cooler temperatures. This spider is relatively abundant within its distribution. Argiope argentata are commonly seen and photographed by hikers in Southern California and the Andes Mountains. == Hunting and diet ==

Hunting Argiope argentata follows a distinct sequence of steps when capturing, killing, and ultimately eating its prey. The first step is localization of the prey, for which the spider's vibration receptors are critical. The second step is immobilization of the prey which involves two steps: wrapping and biting. The second step consists of either a long or short bite depending on the type of prey. The third step is transportation, which involves carrying the prey back to where the spider was alarmed of its presence. In the fourth and final step before feeding, the spider manipulates the orientation of the prey so that it is in the proper positioning for the spider to consume. The determining bite length is an important component of prey immobilization. It is determined by the spider by momentarily touching the prey before biting. This contact allows the spider to determine in some manner what the prey is, and what its immobilization will entail. The species incorporates UV-reflecting silks into its web design which serve as an attractor to their prey. These patterns have been hypothesized to specifically attract prey that engage in pollination. Flowers incorporate UV-reflecting patterns to ensure their pollination by insects. == Webs and silk ==

Webs Like other members of Argiope, silver argiopes often spin stabilimenta into their webs. These often take the form of zigzag lines, Silks Argiope argentata is in the family Araneidae, otherwise known as orb-weavers. == Reproduction ==

Sexual cannibalism Argiope argentata spider engages in sexual cannibalism, during or after copulation, without fail. The act of sexual cannibalism amongst A. argentata has been looked at more closely in the laboratory with virgin females. Upon the first attempt at mating, the female spider thrusts the male spider off of her, which results in his death more than two-thirds of the time. Males that survive, bravely try again, this time with success, only to be met with immediate cannibalism after the act of insemination is completed. Plugging As a consequence of post-coital cannibalism, males generally have a single chance at successful mating. As an evolutionary strategy to ensure gene propagation, they engage in "plugging", in which the male breaks off its copulatory organ, securing it into the female, thus preventing future insemination by rivals. == Behavior ==

Grooming Argiope argentata engages in grooming behavior post prey capture. The duration and intensity of this grooming behavior has a specific connection to the type of prey that was captured. The spider deliberately grooms the tarsal region on each of its eight legs, which is hypothesized to be due to the ability of these structures to respond to chemical changes using chemosensory organs. There is no evidence that A. argentata extends this grooming behavior to the rest of its body. Defecating The act of defecation occurs most frequently after biting the prey or feeding on it, and is a very calculated process. A. argentata consciously widens the space between its abdomen and its web before defecating, to ensure that the web itself is not soiled. A. argentata’s anus is positioned away from the web, so that the defecation itself will be excreted away from the web. Drinking Argiope argentata is found to receive its water supply from the web's surface. The web is able to capture and hold droplets of water for A. argentata to drink. It appears that this is the supplier of water for the spider, regardless of the presence and degree of other environmental conditions. For example, the spider is not reliant on the humidity of the air or the water content of the prey. == Enemies ==

Predators Lizards are significant predators of A. argentata, as can be seen by the so-called "lizard effect". That is, within island habitats, there is a negative correlation between the number of lizard inhabitants and the number of A. argentata. Other predators include wasps and birds. Parasites As skilled web designers and catchers of prey, Argiope argentata are frequently the target of food theft by other species. Dewdrop spiders (genus Argyrodes) are small kleptoparasitic or commensal spiders that can often be found living in the webs of A. argentata, where they feed on insects trapped by their host's web. Due to silver argiopes' poor vision, these intruders are usually able to escape detection and consequences for their trespass and thievery. == Conservation ==

Argiope argentata is not currently an endangered species. These spiders are relatively abundant across a variety of different habitats. Because Argiope argentata can be found across different countries, there are currently no unified efforts to promote the conservation of either the species or the land on which they reside. As has been relatively commonplace, conservation efforts for most natural habitats (including that of Argiope argentata) revolve around reducing greenhouse gas emissions, recycling, and reducing pollution. These efforts will not only sustain the habitats of spiders, but those of countless other species who might be harmed by human action. Argiope argentata are very important for the conservation of certain environments. According to information gathered from the St. Louis Zoo, these spiders help keep insect and pest numbers down as they consume thousands of pounds of them per year. This helps to preserve certain crops and plant life without the need of harmful pesticides. == Extinction patterns ==

Argiope argentata lacks a strong relationship between population size and persistence rates, which results in its high likelihood of sudden extinction regardless of its current population size. The four month long developmental time for A. argentata spiderlings opens the species up to a higher risk of deviation or disturbance in its normal population size. One hypothesis provided for these rampant cycles of extinction and regeneration, is that this constant fluctuation in population size leads to an inevitable outcome possibly hitting zero. == Human bites ==

Argiope argentata are relatively harmless to human beings. If thoroughly and intentionally provoked, these spiders might bite out of self defense. Their venom is not toxic to humans and rarely causes any sort of adverse reactions. In fact, the bites of Argiope argentata are relatively comparable to a bee sting - with only minor redness and occasional swelling resulting. Despite being relatively harmless to humans, the bites of A. argentata can prove deadly to smaller animals such as insects and rodents. They are effective ways for the spiders to kill their prey once they have been immobilized. ==Gallery==

File:Argiope argentata - kerkennah.jpg|Argiope argentata - kerkennah - Tunisie File:Argiope argentata (Galapagos).JPG|Female in the Galápagos Islands File:Silver argiope (Argiope argentata).jpg|Female in Jamaica File:Silver argiope (Argiope argentata) with victim.jpg|Female with victim (a bush cricket) in Jamaica File:Argiope argentata-Silver Argiope.jpg|Female in Southern California ==References==