|Banded Garden Spider - Argiope trifasciata|
Family Araneidae - Orb-Weavers
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Live adult spiders photographed in the wild at Ogle County, Illinois.
Black and yellow garden spiders become very active toward the middle of August here in Illinois. They actually hatch and mature in early summer, but stay mainly out of sight until they are big enough to build their signature web, and set about the business of mating and egg-laying.
Their huge orb webs (up to 2 feet in diameter) can be found nearly anywhere there are weeds. Argiope spiders are carnivorous predators, active in the daytime, attacking insects that become trapped in their web. The spider hangs head down in the center of the web while waiting for prey. Often, she holds her legs together in pairs so that it looks as if there are four big ones. Sometimes the spider may hide in a nearby leaf or grass stem, connected to the center of the web by a nonsticky thread which quivers, alerting her when a customer arrives.
Leg span as pictured = 35mm (1-3/8") - somewhat smaller than A. aurantia
Argiope spiders often add stabilimenta, or heavy zig-zagging portions, to their webs. Stabilimenta are conspicuous lines or spirals of silk, included by many diurnal spiders at the center of their otherwise cryptic webs. It has been shown spider webs using stabilimenta catch, on average, 34% fewer insects than those without. However, webs with the easily-visible markings are damaged far less frequently by birds flying through the web. It is an evolutionary tradeoff the spider can influence every time it builds a new web. The inclusion of stabilimenta is influenced by many factors, including prey density and web location. Read the scientific study at Behavioral Ecology magazine.
Argiope trifasciata is highly visible in her aposematic colors.
This spider is in hurry-up mode. Having just captured a paper wasp (dangerous prey for a spider), she is rapidly pulling silk from her spinnerets with her back legs and wrapping it around the wasp by spinning the prey with her front legs (you can see the "spin axis" formed by the unfortunate insect's legs) . As soon as the prey is immobilized sufficiently, she quickly bites the wasp several times, injecting her venom into the insect's head - avoiding the business end altogether - then retreats to a safe distance and allows the venom to work.
The process takes roughly 15 seconds. When the wasp is completely paralyzed and no longer presents a stinging threat, the spider comes back to finish wrapping her dinner. I thoroughly enjoy watching this macabre spectacle.
Smaller male A. trifasciata build orb webs near their prospective mate.
Class Arachnida / Order Araneae: Spiders are the largest group of arachnids. They are easily recognized by their eight legs, and there are few creatures great or small that elicit such irrational fear in mankind. The vast majority of spiders are completely harmless and offer beneficial services, chief of which is keeping the burgeoning insect population in check. I am continually amazed at the resourcefulness of these supremely successful predators.
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