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The black and yellow argiope is one of the most colorful orb weaver spiders in gardens of southern California. The female is characterized by its large size (body often over 2.5 cm in length) and black abdomen with broad yellow bars along the sides. The spider typically hangs upside-down (head down) in its strong orb web. Below the center is a zigzag band of silk (called the stabilmentum) which may help to camouflage the spider in its web. This species (and others) are sometimes called "writing spiders" because the stabilmentum superficially resembles writing or letters of the English alphabet. The following orb weaver spider does not have a stabilmentum in its web.

The Silver Argiope (Argiope argentata). Family Araneidae

The following orb weaver was photographed on a rosemary bush (Rosmarinus officinalis) in San Marcos. The web consists of both an orb web and an irregular web. The retreat is a tangled, knotted web made with debris and leaves woven into the silk, placed so as to make a small protective tent for the spider. When disturbed it quickly drops out of the leaf cluster retreat and returns when the danger has passed. The genus was identified by Jim Berrian of the San Diego Natural History Museum.

The emerging female fig wasp faces many dangers after she leaves the safety of her protective syconium. One of these dangers during wasp exodus from summer profichi and fall mammoni crops of syconia are predators, including opportunistic spiders. The following three images show a minute orb weaver called the trashline spider (Cyclosa turbinata) that has built its web near a mammoni syconium of Ficus pseudocarica. On September 14, many wasps leaving the syconium fluttered into the web and were quicky caught by the tiny spider. They were immediately rolled into balls of silk and stored in a vertical row in the center of the web.

The black widow (Latrodectus mactans = L. hesperus) is one of the most poisonous spiders in North America. The neurotoxic protein latrotoxin is produced in glands of the cephalothorax and is injected through hollow fangs (chelicerae). Although the mechanism is very complex, alpha-latrotoxin apparently interferes with the normal flow of calcium ions across nerve cell membranes, thus effecting muscular contractions. Latrotoxin is an activator of synaptosomal calcium uptake, while conotoxin from the cone snail (Conus) is an inhibitor of calcium channels, yet both deadly toxins ultimately produce cramping or rigid paralysis. Latrotoxin is more toxic than most snake bites with a lethal dosage (LD-50) of 0.9 mg/kg in mice. [LD-50 is the dosage required to kill 50% of the experimental animals.] If you live in southern California, there is probably one of these spiders near or under your house at this very moment. Chilean scientists have been researching latrotoxin as a treatment for erectile dysfunction coupled with temporary infertility (contraception).

The brown widow (Latrodectus geometricus) is reportedly native to South Africa, although it was first described from South America. During the early 2000s it became well-established in urban Los Angeles and San Diego, particularly the coastal cities of San Diego County. The upper abdomen is mottled tan-brown to gray, often with reddish-orange spots and whitish patterns or geometric designs. In fact, some specimens superficially resemble immature black widows (L. mactans). The legs are often banded in black and yellowish-tan. The hourglass marking on the ventral side of the abdomen is more orange-colored than the black widow. This marking clearly separates it from the harmless false widow (Steatoda grossa) that commonly inhabits houses and garages in southern California). The egg sac is very distinctive and unmistakable. It is covered with pointed protuberances, unlike the smooth sac of the black widow. The sac contain about 80 eggs compared with 300 for the black widow; however, brown widows produce many more egg sacs during their life cycle and consequently many more offspring. In fact their higher fecundity may be one of the reasons why they are displacing black widows in areas where both spiders occur.

Some authorities state that brown widow venom is more potent than the black widow; however, it injects about half as much venom. According to Richard S. Vetter, Department of Entomology, University of California Riverside (2009), the brown widow is less dangerous than our local native black widow. Since both species occupy the same ecological niche, the brown widow may eventually replace the black widow in some areas.

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