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Hey all, this post (and topic) was done for a few different reasons, including general information, projects I have been meaning to do, some good general guidelines for using to differentiate between the two genera, and ease for me to quote when responding to new threads. Hope somebody learns something and hope you all enjoy. Here goes.
Differentiating between Latrodectus and Steatoda species.
Originally Posted by Widowman10 Steatoda species are known as "false widows" for a reason. Some of the darker ones such as grossa and borealis are quite dark and can be confused with widows by the untrained eye. With a teeny tiny bit of practice, you can tell the difference:
Abdomen differences: in Steatoda is generally more flat, while widows have more globular type, "fast-back" abdomens, coming to a point at the spinnies.
Leg differences: in Steatoda are more short in comparison to body, while widows have longer legs. Widows also have a noticeable thinning of the legs in the last segment (tibia is very thick compared to a very thin metatarsus. The same area in Steatoda are tapered down).
Eye pattern differences: not that you can see this without a microscope, but:
is different from
(images courtesy of bugguide.net)
Here is an actual eye pattern picture:
Originally Posted by Bastian Drolshagen
Originally Posted by Widowman10 Alright, here we go. Here is a side-by-side comparison between Latrodectus and Steatoda. Hopefully between these shots y'all can see the differences clearly I tried to pick 2 similar-sized spiders.
Originally Posted by Widowman10 Another comparison of Latrodectus and Steatoda (since someone requested I do the same thing with a grossa). Again, tried to pick 2 similarly-sized spiders.
And just to be clear, patterns and colors are not always good indicators or differentiators between species.
There are no Steatoda species with an hourglass, but not all Latrodectus species have an hourglass.
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