# differentiating between Latrodectus and Steatoda species



## Widowman10 (Oct 21, 2009)

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.*



Widowman10 said:


> 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.
> 
> ...





Widowman10 said:


> from bugguide.com, drawings of eye patterns of Latrodectus and Steatoda, respectively:


here is an actual eye pattern:


Bastian Drolshagen said:


>





Widowman10 said:


> allright, 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.





Widowman10 said:


> 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.


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## Violet (Oct 21, 2009)

This is great! The eye patterns are very interesting. I've been meaning to get some pictures of the Steatoda species over here for you. I’ll get onto it as soon as possible.


Theridiidae is such an amazing family!


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## Widowman10 (Oct 21, 2009)

Violet said:


> This is great! The eye patterns are very interesting. I've been meaning to get some pictures of the Steatoda species over here for you. I’ll get onto it as soon as possible.
> 
> 
> Theridiidae is such an amazing family!


haha, i was cruisin through a couple of old threads and was wondering if you'd forgotten 

and they are!!!


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## Violet (Oct 21, 2009)

I always find heaps when I’m gardening at work, I’ll take my camera next time.


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## jsloan (Oct 21, 2009)

Widowman10 said:


> *differentiating between Latrodectus and Steatoda species.*
> 
> abdomen differences: in steatoda is generally more flat, while widows have more globular type, "fast-back" abdomens, coming to a point at the spinnies.


_Steatoda grossa_ is an exception to this.  Here's a drawing I made many years ago of mature male and female _S. grossa _, showing the shape of the abdomen.  The female is very much like what you described for _Latrodectus_.  _S. borealis_ is distinctly "flatter," though:


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## Venom (Oct 21, 2009)

Widowman...


:clap: :clap: :clap: :clap: :clap: :clap: :clap: :clap: :clap: :clap: :clap: 


VERY nice work!! This is really a great guide--you should submit this to the Articles forum.

Extra kudos for the brilliant side-by-side picture comparisons.


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## Widowman10 (Oct 21, 2009)

jsloan: yes grossa is a little more "widow-like" and that's why i posted pics with a grossa (it was you who prompted me to before ). but there are still plenty of differences and those differences are still enough. and borealis is a bit flatter, yes.

venom: thank you sir :worship:


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## jsloan (Oct 21, 2009)

Widowman10 said:


> jsloan: yes grossa is a little more "widow-like" and that's why i posted pics with a grossa (it was you who prompted me to before ). but there are still plenty of differences and those differences are still enough. and borealis is a bit flatter, yes.


I understand; and I was just pointing out some similarities, not trying to criticize your presentation per se.  _S. grossa_ is not called the "false widow" for nothing.  

What about the hourglass marking as another way to tell these genera apart?   You have more experience with _Latrodectus_ than I do.  Is the presence of an hourglass a distinguishing feature (I do know it's absent in some _Latrodectus_ individuals)?  Is there any _Steatoda_ species with an hourglass?  I could be wrong about that.  I haven't seen every species of _Steatoda_.  In another words, if there is an hourglass would you say it is safe to say the spider is _Latrodectus_?

Good presentation, BTW!


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## Rick McJimsey (Oct 21, 2009)

jsloan said:


> (I do know it's absent in some _Latrodectus_ individuals)?


I have an _L.hesperus_ female that has no hourglass; I'm sure it's quite common, but it's still pretty cool to see. I'll try to get some pictures up.


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## Widowman10 (Oct 21, 2009)

not a distinguishing feature:







i have more to comment on, but it has to wait till later tonight.


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## Bastian Drolshagen (Oct 22, 2009)

eyepattern:


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## Widowman10 (Oct 22, 2009)

jsloan said:


> What about the hourglass marking as another way to tell these genera apart?   You have more experience with _Latrodectus_ than I do.  Is the presence of an hourglass a distinguishing feature (I do know it's absent in some _Latrodectus_ individuals)?  Is there any _Steatoda_ species with an hourglass?  I could be wrong about that.  I haven't seen every species of _Steatoda_.  In another words, if there is an hourglass would you say it is safe to say the spider is _Latrodectus_?


coming back to this again, the topic of hourglasses. not all latrodectus species have an hourglass. some have a nice glass, some have no glass, others have wierd patterns or boxes. 

there are no steatoda species with an hourglass.

and yes, it is safe to say that if you see an hourglass on a therid-looking spider, it's a latro. 

but also, to throw this out there, some steatoda can look similar to some latrodectus dorsally.



jsloan said:


> Good presentation, BTW!


thanks!


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## jsloan (Oct 22, 2009)

Widowman10 said:


> but also, to throw this out there, some steatoda can look similar to


That's a beautiful spider!  When I was kid I lived in Teheran, Iran for a few years.  This exact species was common there and my brother and I collected many and brought them home as "pets."  They are a little smaller than _Latrodectus_, about the size of _S. grossa _, if memory serves.  The contrast between the bright orange markings and the sleek black background makes them one of the most beautiful spiders I've ever seen.  Pictures hardly do them justice.  Also, as I recall, many or most immature females had dullish yellow markings, which only changed to orange upon the final molt.

Great picture!


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## Widowman10 (Oct 22, 2009)

jsloan said:


> That's a beautiful spider!  When I was kid I lived in Teheran, Iran for a few years.  This exact species was common there and my brother and I collected many and brought them home as "pets."  They are a little smaller than _Latrodectus_, about the size of _S. grossa _, if memory serves.  The contrast between the bright orange markings and the sleek black background makes them one of the most beautiful spiders I've ever seen.  Pictures hardly do them justice.  Also, as I recall, many or most immature females had dullish yellow markings, which only changed to orange upon the final molt.
> 
> Great picture!


the contrast is pretty sweet, but you should see L. elegans!! (or sp. laos, which is probably the same thing). absolutely stunning.


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## David_F (Oct 22, 2009)

Great thread!  I second the motion that it should be submitted to the articles section.

You mentioned different leg lengths between the two genera.  Would it be possible for you to post a leg length pattern for them (between the two genera and also between males and females of each)?  Average in mms and longest to shortest?  When you have time and safe specimens to work with, of course.  Por favor?

One day I'm gonna start back up with spiders but until then I have to just read about them.


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## Widowman10 (Oct 22, 2009)

David_F said:


> Great thread!  I second the motion that it should be submitted to the articles section.


wow, thanks! :worship: 



David_F said:


> You mentioned different leg lengths between the two genera.  Would it be possible for you to post a leg length pattern for them (between the two genera and also between males and females of each)?  Average in mms and longest to shortest?  When you have time and safe specimens to work with, of course.  Por favor?


if you can clarify a few things for me, i would be more than happy to.

but before we do, there's a few things to keep in mind. the first thing that pops into my head is about the MM's. males will mature at different instars and certainly different sizes. in one latrodectus species, i recall males maturing anywhere from the 5th to the 7th instar!  i've had MM's that were tiny (3/4") and some that were huge (1 1/4"). same species of course. 

i think i understand what you are asking, but there are many variables. are you asking for general patterns, such as leg 1 are much longer than leg 2, and leg 4 are shorter than leg 1, but longer than leg 2 and 3? or are you asking about something else? and also, this will vary in species (grossa vs. borealis / variolus vs. mactans). 



let me know and i'd love to do it!


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## David_F (Oct 22, 2009)

I realize there will be variation in adult size so I guess average length isn't the way to go.  But what about the leg length pattern (i.e. leg I, leg III, leg IV, leg II, longest to shortest....that pattern is completey arbitrary)?  Would that hold true regardless of adult size?  I know it's been used for other genera, Loxosceles for instance, but I don't know how reliable it is.  

I don't know if that makes any sense.  Need to get to bed so I'm trying to think and type fast.


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## Widowman10 (Oct 22, 2009)

David_F said:


> I realize there will be variation in adult size so I guess average length isn't the way to go.  But what about the leg length pattern (i.e. leg I, leg III, leg IV, leg II, longest to shortest....that pattern is completey arbitrary)?  Would that hold true regardless of adult size?  I know it's been used for other genera, Loxosceles for instance, but I don't know how reliable it is.
> 
> I don't know if that makes any sense.  Need to get to bed so I'm trying to think and type fast.


leg length pattern would definitely hold true regardless of different-sized individuals. i'll search for a minute and see what i can find. if i can't find anything, well...


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## Rick McJimsey (Oct 23, 2009)

Here we go..


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## loxoscelesfear (Oct 24, 2009)

Really informative thread.  Have one living in my front door frame doing pest patrol.  I once crawled under a church rumored to have "black widows" throughout the crawlspaces.  Not surprisingly, the "black widows" were _grossa _. Anywho, another interesting thing about _grossa_ is there longevity: up to 6 years.  Wow.


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## Widowman10 (Oct 24, 2009)

hahaha, beautiful rick!! :clap: a fat nice female tred.


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## buthus (Oct 26, 2009)

Steatoda..the genes for the hrglass is there.  More ancient/primitive? or maybe still developing if needed and its probably not needed?   
This one "thinks" it sorta needs it...


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## Rick McJimsey (Oct 26, 2009)

Wow, very interesting, buthus!
Is this the Steatoda sp. "Wastelands pumpkin"?

Ventral on S.grossa


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## Widowman10 (Oct 26, 2009)

looks like the abdominal pattern could be similar to corallinus. i've still yet to see anything that is hourglass in shape though from steatoda. good pics though buthus, and nice shot rick.


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## buthus (Oct 26, 2009)

Rick McJimsey said:


> Wow, very interesting, buthus!
> Is this the Steatoda sp. "Wastelands pumpkin"?


Yep... whats the latin translation for "pumpkin"? :?   

Only a few widow species (seems the n.americans) have retained "hour glass" markings that look like 2 triangles w/points touching.  We want to believe its a refinement ...triangles/angles catch the eye ..like warning signs on the side of the road.  But...thats only a secondary development ...color retention...a helpful one yes..but the shape is due more to the body construction imo.  You can see it in most trues.  


Widowman ...ID this one for me...


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## Widowman10 (Oct 26, 2009)

you going to give me any more info besides just 1 pic?! 

can't nail something down with just one picture. you can get pretty close with some species though.

whatcha aiming at steven?

it is from south america


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## buthus (Oct 27, 2009)

Widowman10 said:


> you going to give me any more info besides just 1 pic?!
> 
> can't nail something down with just one picture. you can get pretty close with some species though.
> 
> ...


probably...probably not. (edit:just kiddin...obviously a s.a. widow!  )..packing for a quick trip to Ecuador ...ill look around and see what i see.  leaving in the morn...cant talk anymore 'bout this fun stuff.
edit: 


> can get pretty close with some species though.whatcha aiming at steven?


arrr ...thars the fun of it isnt it?    pretty close is god enough   er... good enough  i mean.


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