Arthropods 1b

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Southern California Arthropods (Mostly) #1: Spiders 2
© W.P. Armstrong 15 April 2009
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Trapdoor Spider Family (Ctenizidae)

Nest of a trapdoor spider compared with U.S. penny (diameter 19 mm).

California trapdoor spider (Bothriocytum californicum) inside its nest.

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.

Male California trapdoor spider (Bothriocyrtum californicum) and its burrow.

Some Other Interesting Arthropods
See The Amazing Kissing Bug


Tarantula Family (Theraphosidae)

Large California tarantula (Aphonopelma sp.) from Twin Oaks Valley.

Close-up view of tarantula chelicerae (jaws) each tipped with a large hollow fang.

Enlarged view of the tip of a fang showing canal for injecting venom (white arrow). The
beveled tip and hollow core are remarkably similar to a hypodermic syringe (see inset).

A recently deceased tarantula found on Owens Peak north of Palomar College.
I can't be sure that this tarantula was killed by a tarantula hawk wasp (Pepsis).

See Tarantula Hawk Wasp (Pepsis)

Brazilian white-knee tarantula (Acanthoscurria geniculata).


Cobweb or Cellar Spider Family (Pholcidae)

A cobweb spider (Pholcus phalangioides) in its web.

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)

See The Long-Legged Crane Fly


Wolf Spider Family (Lycosidae)

A wolf spider (Pardosa sp.). Its body is about 10 mm in lenth.

A giant wolf spider (Hogna carolinensis) in San Marcos, San Diego County. The body of females can be up to 35 mm in length. This one is about 30 mm. The U.S. penny is 19 mm in diameter. With the exception of tarantulas and trapdoor spiders, this is one of the largest (and fastest) spiders in San Diego County. It is definitely a surprise when you see one run across your carpet!

See Penny Used In Wayne's Word Size Relationships


Another Large Wolf or Grass Spider In My Office


Grass Spider Family (Agelenidae)

A grass spider or "corner spider" (Hololema curta) in its web.


Dysderid Spider Family (Dysderidae)


Click on the photograph to see this spider with concrete background removed.

The infamous sow bug killer (Dysdera crocota). Originally native to Europe, it now has a worldwide distribution. This formidable-appearing spider lives under stones or debris on the ground. It does not spin a web for entrapping prey but instead hunts for sow bugs and pill bugs (isopods) in cracks and crevices. It uses its extra large powerful fangs to pierce and feed on these hard-shelled crustaceans. It is a beneficial spider, but can bite if handled carelessly. The venom is not dangerous to humans, but may cause a local allergic reaction that includes stinging and itching. One Internet reference describes the bite as "annoying." Probably its main enemy in coastal San Diego County are colonies of relentless Argentine ants.

The enormous chelicerae (jaws) and fangs of the sow bug killer (Dysdera crocota).
Note the ring of 6 small eyes that are not as well-developed as in jumping spiders.

Sow Bug Eater Holding Its Favorite Prey
A Pillbug: Another Prey Of Sow Bug Eater
More Information About The Argentine Ant


Lynx Spider Family (Oxyopidae)

A green lynx spider (Peucetia viridans) with its prey. It was photographed in bed of shasta daisies (Chrysanthemum maximum) with a Sony T-9 digital camera. The camera was held with one hand and extended at arm's length.

A green lynx spider (Peucetia viridans) with its prey.

A green lynx spider (Peucetia viridans) with its prey.

A striped lynx spider (Oxyopes salticus).

More Images Of The Green Lynx Spider


Huntsman Spider Family (Sparassidae)

A golden huntsman spider (Olios fasciculatus).

Male Golden Huntsman

Male golden huntsman. Note pedipalps with enlarged claw-like tips.

Giant Huntsman

A well-camouflaged giant huntsman spider (Olios giganteus) on the bark of an oak.

A giant huntsman (Olios giganteus) in ominous pose on window frame.


Sac Spider Family (Clubionidae): Miturgidae in some references

A small house spider of the genus Cheiracanthium, a member of the sac spider family (Clubionidae). The body (excluding legs) is about 5 mm long. These spiders are pale or cream-colored with translucent legs. Members of this family spin saclike, tubular resting sites inside a rolled leaf or under bark or a stone. The house-dwelling species builds its saclike silk bivouac in corners, crevices or even inside appliances. Some members of this family can inflict a painful bite. Their long, sharp fangs can readily penetrate human skin. Their venom contains a cytotoxin that destroys tissue, and bite wounds are slow to heal. The most common species found in homes in southern California is C. mildei which is introduced from Europe. They have 8 conspicuous eyes arranged in two rows.

Business end of the sac spider (Cheiracanthium mildei) showing chelicerae (jaws) & fangs.


Crab Spider Family (Thomisidae)

     Crab Spider on Brodiaea       Crab Spider on Hulsea      Crab Spider on Milkweed 


References:

  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.

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