black spider with white and yellow spots / marks – poisonous spider identified

most poisonous spiders

Identified a poisonous widow spider with white marks or spots on a large abdomen.  Pictured below is a venomous spider that belongs to the Latrodectus genus, in the Theridiidae family. 

identify black widow spider
black striped spider with white marks, spots

Latrodectus is a genus of spider which contains 32 species. The more common name is WIDOW SPIDERS.

Widow spiders belong to the cobweb spider family. They spin irregular, sticky webs to catch insects. Widow spiders possess a row of bristles on their hind legs that form a comb, which is easily seen in the photos. The comb is used for flinging silk over its prey.

The black widow poisonous spider is perhaps the most common of the genus. Widow spider bites are dangerous because of the neurotoxin which causes the condition latrodectism(pain, seizures in muscle groups) —  this is where the name for the spider genus came about,Latrodectus.

The female Latrodectus spiders have unusually large venom glands and its bite is particularly harmful to humans; however, Latrodectus bites rarely kill humans if proper medical treatment is provided.

widow spider
black spider with orange yellow hourglass

Symptoms of a poisonous widow spider bite:

Once the spider’s poison reaches the blood, the venom is moved by circulation, causing its toxins to be deposited in the ends of the nerves that are inserted into the muscle.

The spider’s venom acts at nerve endings to prevent relaxation of muscles, causing seizures —constant, and painful muscle contractions. Cramping in the stomach is frequently the most severe but leg and back muscles may be affected also.

What to do after being bit by a widow spider?  SEEK medical attention after a poisonous spider bite.

spider with white spots
black striped spider with large abdomen

Most people will recognize widow spiders by the hourglass markings on the underside of their abdomens. The hourglass mark is NOT present in ALL Latrodectus species.

hourglass on spider belly
hourglass on black spider belly

In arid parts of ArizonaLatrodectus spiders inhabit almost every crevice in the soil and nests can be found in cholla cacti and agave plants.

The female’s spider venom is at least three times more potent than that of the males.  


Author: tjsgarden

We are a family that loves the Arizona Desert. A lot of research and team efforts go into our articles and photos. Come discover the beauty and mystery with us. Don't forget your sunscreen!

One thought on “black spider with white and yellow spots / marks – poisonous spider identified”

We love your comments and questions!

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s