Spiders of the Pacific Northwest Lowlands

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Crab Spider Cross Spider Cellar Spider Jumping Spider Wolf Spider
 
Giant House spider Common house spider Long jawed Orb Weaver Callobius  

 

 
Crab Spider   Misumena vatia  Family Thomisidae

Identifying Features:  First two pairs of legs long, stout and forward pointing, oval abdomen with red marks on the side.

This crab-like spider weaves no web, rather she waits in ambush in flowers.  To improve the odds this spider can slowly change colors to help in blend in with its background.  Crab spiders can be either yellow or white, and the young spiders change colors much faster than older ones. They also change to white faster than to yellow.  As a bee or other insect approaches the spider will crouch down on its hind legs, then once the victim  is within range she will pounce and bite.  This spider has a powerful and fast acting venom which subdues the prey which is then eaten.  The males are much smaller than the females and roam from flower to flower seeking a female to mate with. 

Although they do not spin webs, they do have the ability to create a single thread which they use for escape.  If threatened, they will drop off the flower and use the thread to keep from falling too far, often swinging up on the thread to hide under a leaf or other protection.
 


 

 
European Cross Spider  Araneus diadematus  Family Araneidae

Identifying Features: Orb web weaver, with white "cross" on the back of the abdomen

This is perhaps one of the most common spiders in our area and by fall the females can be very large. Cross spiders make large orb shaped webs and typically rebuild most or all the web each day.  The radial lines which make up the main support structure of the web can stretch considerable distance.  When creating these lines the spiders take advantage of the prevailing morning winds and so the orientation of the webs indicates  the morning wind pattern.  There may be more than a hundred webs in a typical suburban yard.

The females perch upside down in the web and wait for a victim which they immediately immobilize with venom, then wrap in silk.  The male spiders are less than half the size of the female and approach the mating business with a great deal of caution so as to not become dinner instead of a mate.   In the late summer and fall the females create a yellowish fuzzy egg sac which in spring hatches hundreds of tiny spiderlets. The tiny spiders will stay in a compact cluster for a few days before disbursing.  For more information click here.
 
Cellar Spider   Pholcus phalangioides  Family Pholcidae

Identifying Features: Long legs, white line through abdomen, found in houses.

This is a spider of the tropics which has become widespread in houses throughout the world. It makes cobwebs in the corners of houses where it hangs upside down patiently waiting for a meal.  Cellar spiders feed on mosquitoes and other small flying insects, and also eat other smaller spiders. If food becomes scarce, they will hunt each other until only the largest spider remains.  The males travel from web to web to mate, and females store sperm, sometimes for months.  The females may lay eggs any time of year and carry the egg sac under her body just under her head.

Egg production is probably linked to food supply which is greater during the summer months. When the eggs hatch, the tiny spiderlets will be tended by the female for about 9 days until their first molt and then they will leave and find their own corner.   If disturbed this spider will either drop to the ground and scurry under cover or shake its web rapidly so that it becomes a blur of motion. There is a myth that this is the most deadly poisonous spider but it is safe because it can not bite people.  This is false; the venom is relatively weak, and this spider could bite people but like all spiders, it has no reason to do so.
 
Jumping Spider    Family Salticidae

Identifying Features: Two large eyes, and two smaller eyes facing forward, moves in jumps.

This spider has excellent vision and if you wave a finger in front of it it will track the motion.  They have a system of hydraulic fluid in their legs which allows them to jump several  times their body length. When they jump they often attach a silken thread as a "belay line" and if they miss their target this keeps them from falling too far.  They hunt by running down their prey and leaping on it, sometimes from several inches away. Their excellent vision can locate prey at a considerable distance and they actually stalk like a cat, slowly creeping up then pouncing.  While hunting they have an amazing speed and dexterity, easily dodging around or leaping over obstacles.   During mating the males perform a series of movements to engage the female, and some species make sounds like drumming. Recent research shows that in some species, the females responds to the reflection of UV light off the male.  Eggs are laid in a silken cocoon under a leaf or in other cover and the female will guard the eggs until they hatch. 

 
Wolf Spider   Family Lycosidae

Identifying Features: Large, hairy spider found on the ground

This is a ground dwelling spider found in meadows, forests, and shorelines.  There are many different kinds but all of them hunt by stalking and running to capture their prey.  They are commonly found on warm days along cobbled river shores.  They have no nest, rather the female carries the egg sac around with her until it hatches, and then the young spiderlings ride on her back for several days before dispersing.

 
Giant House spider  Hobo Spider  Tegenaria duellica, Tegenaria agrestis

Identifying Features: Large spider in and around houses and buildings

This spider causes consternation in homes throughout our area each fall as the males come out of the shadows and boldly scamper about the house in search of mates. These spiders are among the fastest invertebrates and tend to be nocturnal, so when you turn on the light, they often will be seen running for cover.  During the search for a mate they sometimes fall into bathtubs or sinks and are unable to crawl out, although they have no problems crawling up walls.  They have large pedipalps in the front which people mistake for giant fangs.  You can use these structures to determine the gender, the males pedipalps end in little round structures, the females are pointed. Females have bigger bodies but shorter legs than males.  This spider makes funnel webs in basements, gardens, and near water and other cool places. It  eats insects and other spiders.  The hunting strategy is simple, the spider sits and waits in its web until prey wanders into it then it rushes out to secure the meal.

Another almost identical spider is the hobo spider.  This spiders venom contains a powerful toxin which causes cell death around the bite and can also cause flu like symptoms in some people.  It takes a very close up look to tell them apart.

For detailed information about identifying Hobo and Giant House spiders click here

 
Common House Spider  Parasteatoda Tepidariorum  Family Theridiidae

Identifying Features: Large abdomen with spotted legs

This is another spider which lives in our homes. Its large ovalish shaped abdomen has a delicate pattern of swirls of brown and white.  It makes dense tangles of  webs and it lives its entire life inside this web. Because of its large abdomen it can not easily move on the ground and good locations often attract several spiders.  The females make oval shaped egg sacs which house up to 500 eggs. The young spiders quickly disperse using a long slender thread which carries them away from the nest,  however  many of them get eaten by adjacent spiders.

 
Long Jawed Orb Weaver   Tetragnatha species  Family Tetragnathidae

Identifying Features: Long legs, long narrow striped abdomen, often in grass

This delicate spider makes small webs, often between small plants and grass near the ground.  The family is called long jawed because some of them have mouth parts which are as big as or even bigger than their heads.  When disturbed these spiders will align all their legs in one plane, making them look like twigs. More often when disturbed they quickly drop out of sight.

 
Callobius severus   Family  Amaurobiidae

Identifying Features: Very reddish legs, dark hairy abdomen.

This  spider is found under logs, inside bark and in bark crevasses. It also makes its way into houses at the edges of woods, and loves to live under piles of old boards.  It makes a thin funnel web.