Monday, September 14, 2009

Arrowhead Spider

 
This gorgeous spider is called the Arrow-shaped Micrathena (Micrathena sagittata). Relatively small in size, but remarkable in their coloring. They reach about 3/8 inch in length. The females have an arrow-shaped abdomen from whence they get their name, this abdomen has three pairs of pointed tuberacles, with the rear pair being large and spreading, it is this spreading that gives them a triangular or arrowhead shape.The tuberacles are tipped with black and are red at the base. The center of the abdomen is bright yellow in color, the cephalothorax is reddish in color with a light yellow stripe down the side.  The males are smaller and lack the tuberacles. 


These spiders can be found throughout the Eastern United States and South America. They are also in Texas and Nebraska. Females build webs near timbered areas, and sometimes gardens. The web will have a hole in the center and a stabilimentum located at the top of the center hole. It is presumed that the hole is to allow for freedom of movement, and that the stabilimentum aids in strengthening the web. The bright color of this spider probably helps protect it from predation from birds, lizards, and most insects. Although, mud daubers are known to prey upon this spider. They paralyze it, and carry it back to their mud nests as a provision to their offspring. Despite their bright coloring they are completely harmless to humans, as are all spiders within this genus. This is an amazingly beautiful spider, and I feel very fortunate to have found one.

11 comments:

  1. Great shots of this arrowhead spider. I found two in my garden today! Ann (middle Tennessee)

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  2. Is it possible their range has expanded...I swear I have seen one in Southern Ontario, Canada. I will post pics...

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  3. Thank you for the comment, this is the one and only time I've ever seen this particular species and I thought it was beautiful

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  4. Melanie, anything is possible, especially with insects and spiders. With the way that people travel, many species get transported with them, often times far away from their original range. I would love to see your pics. You might submit your image and location to www.spideridentification.org They are experts who help ID spiders for individuals. They may be interested in your spider, if it is indeed a Micrathena sagittata I am sure they will want to document the location.

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  5. I'm so glad I found this!! This spider has built a web on a window of my house! It looks EXACTLY like these pictures. I live in Alfred, Maine. I wasn't able to get a good picture but I will look into www.spideridentification.org to add my location to their map.

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  6. I got a great pic of 1 while doing work in Wisconsin Dells

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  7. I got a great picture of one as well! 7/29/13 near the New Jersey Shore,USA

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  8. My son has SEVERAL in his garden. We live in upstate NY. Beautiful but creepy until we found out what it was!

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  9. This does not look like an arrowhead spider, this appears to be more of a Crab Orb Weaver/Spiney Orb Weaver : http://www.bing.com/images/search?q=crab+orb+weaver&FORM=HDRSC2 if you scroll down you will see a picture more similar to the spider you have posted. This is an arrowhead spider :
    http://davesgarden.com/guides/bf/showimage/12405/

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  10. SCRATCH THAT!!! I found it! It's a Arrow Shaped Micrathena! (not arrowhead)...cool spider!

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  11. Me and my little brother both got bit by them

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