Jul 31, 2012 – A Pattern Not So Unique


What type of spider has an hourglass shape on its back? I have tried to look up information on the internet and it either says it's the black widow, which I know has the hourglass on the belly, but other information that pops up is The Redback Spider. Is this the spider that we are seeing? I have had people tell me they have them in the Fayetteville, NC area and we have seen them in the Salisbury, NC area. I would like to know what this is exactly. Many customers only know the hourglass and if they see it on the back they call in a panic about the widow spider. I want to make sure I am knowledgable for my customers as well as myself. How are we able to control these spiders as well. Is there a website that I can get more information from?


This is the problem with customers having just a little bit of knowledge on a topic. First, black widows are so common in California that I suspect nearly every home has a few of them hanging around, and I have been into warehouses (empty, fortunately) where a PMP killed hundreds of them. Frankly, while I will not live with widow spiders in close company their presence does not send me screaming from the home. Our phobia here in California is the Violin Spider which, interestingly enough, does NOT LIVE in California. I guess we most worry about the things that do not exist. 

First, the Redback Spider is a black widow species - Latrodectus hasseltii - in Australia, and as far as I know it has never been found in the U.S. But, the female is the same shiny black of our widow spiders and the difference is that red marking on the dorsal side of the abdomen instead of underneath. The basic description of an "hourglass" marking from your customers probably reflects the basic knowledge they have of spiders, knowing that the widow spiders have this hourglass shape and thus they refer to that shape anytime they see something that resembles it. In fact, there are a lot of very different spiders that have patterns on top of their abdomen or thorax that could be described as kind of like an hourglass, including many of the ground spiders, some jumping spiders, wolf and crab spiders, and probably even some of the Orb Weaver spiders if the person seeing it is not familiar with these different kinds. 

There also now is the Brown Widow spider - Latrodectus geometricus - that is common in Florida and becoming widespread in California. It is a mottled gray-brown instead of shiny black but otherwise has the same basic body shape and long legs of the black widows, and a reddish-orange hourglass on the ventral side of the abdomen. Perhaps your customers are even seeing their spiders from the underside, but mistaking it for the top. 

There are so many different kinds of spiders that making a guess as to the ID of yours could easily be wrong and lead you astray. Better would be to take some examples to your local department of agriculture or university entomology museum and get a positive ID. That will enable you to get specific information on the proper spider and to be able to reassure your customers that the only really dangerous spiders in North America are the widow spiders. Even the Brown Recluse hazard is terribly overblown, although its bite can be serious to sensitive people. 

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