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 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 (contraseption).

The tubular burrow of a trapdoor spider may be six to ten inches deep (15 to 25 cm) with walls lined with a smooth, silken web. The entrance is capped with a very tight-fitting lid which is hinged on the uphill side. The spider holds the door shut with its chelicerae and then suddenly opens the door and grabs a hapless passerby. Trapdoor spiders prefer to build their nests on sunny, south-facing hillsides, preferably in adobe-type soils. Very few spiders are known to actually dig their nests in the ground. Unfortunately, the coastal sage scrub habitat in southern California where trapdoor spiders live is rapidly being converted into housing developments.

The cobweb spider (Pholcus phalangioides) is a common domestic spider introduced from Europe. It is the major contributor of unsightly cobwebs under the eaves of homes and in the ceilings of rooms. When disturbed, it gyrates in its web, presumably to scare away potential predators. In San Diego County, a graveyard of dead Argentine ants in the corner of a room is evidence of a cobweb spider perched high above on the ceiling. Cobweb spiders belong to the order Araneae along with most spiders. The true "daddy long-legs" or "harvestmen" belong to the order Opiliones. In southern California, our two common genera of harvestmen are Protolophus and Leuronychus. An insect that is incorrectly called a daddy long-legs is the common crane fly (Tipula planicornis)

1. Evans, A.V. 2007. Field Guide to Insects and Spiders of North America. Sterling Publishing Co., Inc. New York, New York.

2. Evans, A.V. and J.N. Hogue. 2004. Introduction to California Beetles. University of California Press, Berkeley, California.

3. Hogue, C.L. 1993. Insects of the Los Angeles Basin. Natural History Museum of Los Angeles County.