# Minor Sexual Dimorphism in Monocentropus balfouri



## TexasTreeViper (Jul 19, 2011)

While looking through pictures of sub(adult) M. balfouri I began to notice a trend between the sexes. It seems that in male specimens the blue coloration on the legs extends almost all the way up towards the carapace whereas female coloration tends to stop just above the femur. Here are two really good pictures by Tom Patterson that reprensent what I'm talking about:

Male
http://www.net-bug.net/apps/photos/photo?photoid=95426039

Female
http://www.net-bug.net/apps/photos/photo?photoid=95426036

Has anyone else noticed this before and if so, does it hold true for all individuals and can it be somewhat (though not 100%) of a method for sexing?


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## Singapore_Blue1 (Jul 19, 2011)

TexasTreeViper said:


> While looking through pictures of sub(adult) M. balfouri I began to notice a trend between the sexes. It seems that in male specimens the blue coloration on the legs extends almost all the way up towards the carapace whereas female coloration tends to stop just above the femur. Here are two really good pictures by Tom Patterson that reprensent what I'm talking about:
> 
> Male
> http://www.net-bug.net/apps/photos/photo?photoid=95426039
> ...



That is a mature male bud.....


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## TexasTreeViper (Jul 19, 2011)

Singapore_Blue1 said:


> That is a mature male bud.....


I'm confused by this comment. The pictures are clearly labeled by me and in the link themselves.


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## Hobo (Jul 19, 2011)

I think he's pointing out the obvious dimorphism between mature females and mature males... Assuming that first picture is of a mature male. I thought you were talking about dimorphism between females and sub adult males.


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## TexasTreeViper (Jul 19, 2011)

I've noticed even in subadult males that the coloration extends past the femur. I don't see why this is so confusing.


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## Singapore_Blue1 (Jul 19, 2011)

TexasTreeViper said:


> I've noticed even in subadult males that the coloration extends past the femur. I don't see why this is so confusing.


Well the picture you gave of the male is clearly a mature male...So if your talking about seeing a clear difference between a mature female and a immature male I would like to see a picture to back up that claim...


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## TexasTreeViper (Jul 19, 2011)

Singapore_Blue1 said:


> Well the picture you gave of the male is clearly a mature male...So if your talking about seeing a clear difference between a mature female and a immature male I would like to see a picture to back up that claim...


I have an immature male that just molted last week. He is only ~2.5" but all ready showing extended leg coloration. I can take a picture of him with a size reference but I cannot prove to you it's a male by the molt because I pretty much destroyed it in the process of sexing it. I will take a picture of him later tonight after I get off work and post it so you can see. In the meantime, I will see if I can't find some examples online.

Reactions: Like 1


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## AbraxasComplex (Jul 19, 2011)

To come to the aid of the OP, here are some pictures of an immature male I just took that exhibits the slight sexual dimorphism. He is quite ready for a molt, but notice the extension of blue on the femurs. 




















<edited>

Reactions: Like 2


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## TexasTreeViper (Jul 20, 2011)

@ Abraxas: I appreciate you coming to aid in my absence. Unlike some people on this site I have a life outside the AB and I got too preoccupied yesterday to post the pic so thanks again.

@ Goomba: It's people like you that really degrade this site. I asked an honest, intelligent question and individuals such as yourself try and belittle me yet the countless noob questions such as "What T should I get next?" get pages of responses from people offering help. That makes absolutely no sense. The lack of serious, intelligent conversation on this site is rediculous! So unless you have something of true worth to add to this thread I suggest you keep your little remarks to yourself. <edited>

Here's the pic:

Reactions: Like 3


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## synyster (Jul 20, 2011)

Usually people use a quarter for size reference on pictures.... That being said, sir, I like your style :worship:

On topic: Of course, any MM can be picked out by looking at it, but I too have noticed that M.balfouri IM's tend to have the blue extension on the femur. I even thought this was a common trait of differenciation up until now... Of course the spermathacae will be a 100% confirmation but so far I think this is a really good way to get the idea until getting that "still in good shape" exuvium.


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## TexasTreeViper (Jul 20, 2011)

Thank you synyster for your compliment and comment. This site needs more responses such as your own.


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## xhexdx (Jul 20, 2011)

Good news:  I learned something new.

Bad news:  If it's 100% accurate, Becca's balfouri is male.  :}

Thanks for posting, TTV.


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## Protectyaaaneck (Jul 20, 2011)

Pretty sure the carapace color on males is much lighter as well.


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## fartkowski (Jul 20, 2011)

That's interesting.
I will have to be on the lookout for this when mine grow a bit.
Thanks for posting this TTV.


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## Hobo (Jul 20, 2011)

Neat.

How early can you notice it?


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## xhexdx (Jul 20, 2011)

I just looked at a couple of my 2" balfouri and they're still to brownish for me to tell.  I'm hoping they will have more vivid coloration after their next molt.


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## TexasTreeViper (Jul 20, 2011)

I've had this guy for almost 2 months now and this was his first molt in my care. Looking back at pics taken when I first got him show the extended coloration. Going off of Joe's comment I would guess pretty early on once they start showing adult coloration. I wish I had a few more so I could do a better comparison.


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## xhexdx (Jul 20, 2011)

I have 6 that are around the 2" mark.  I'll keep an eye on them and compare coloration to molts, to help to either prove or disprove this theory.

Reactions: Like 2


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## jonk9194 (Jul 23, 2011)

This is a very enlightening and intellectual thread. I wish there were more topics like this on AB. 

Kudos to the OP for this thread and knowing what tarantula he is going to get next!

Reactions: Lollipop 1


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## Jacobchinarian (Jul 25, 2011)

I read this 1 day to late, I have an m balfouri I bought at the ats conference and it is on it's way home in the mail now. I'll see tommarow and post my findings.


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## xhexdx (Jul 26, 2011)

Just my opinion here, but...

This does *not* confirm anything.  I feel it's still all speculation, and we need a 100% success rate with regard to this dimorphism and then confirming by molt.  I also certainly don't think people should post their balfouri for sale confirming gender based on this, at least not until it is proven.

Just my two cents.


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## TexasTreeViper (Jul 26, 2011)

xhexdx said:


> Just my opinion here, but...
> 
> This does *not* confirm anything.  I feel it's still all speculation, and we need a 100% success rate with regard to this dimorphism and then confirming by molt.  I also certainly don't think people should post their balfouri for sale confirming gender based on this, at least not until it is proven.
> 
> Just my two cents.


I completely agree.


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## Travis K (Jul 26, 2011)

TexasTreeViper said:


> @ Abraxas: I appreciate you coming to aid in my absence. Unlike some people on this site I have a life outside the AB and I got too preoccupied yesterday to post the pic so thanks again.
> 
> @ Goomba: It's people like you that really degrade this site. I asked an honest, intelligent question and individuals such as yourself try and belittle me yet the countless noob questions such as "What T should I get next?" get pages of responses from people offering help. That makes absolutely no sense. The lack of serious, intelligent conversation on this site is rediculous! So unless you have something of true worth to add to this thread I suggest you keep your little remarks to yourself. <edited>


This was a great thread till YOU got all offended.  If you want "serious, intelligent conversation" maybe you should swallow a little bit of your own medicine and respond in the same way you would like others to respond to you.  Take ^that as constructive criticism

That being said... these are great observations and I am sure a lot of M. b. owners, sellers, buyers can and will benefit from it.  Good job guys!

Cheers,


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## TexasTreeViper (Jul 26, 2011)

Travis K said:


> This was a great thread till YOU got all offended.  If you want "serious, intelligent conversation" maybe you should swallow a little bit of your own medicine and respond in the same way you would like others to respond to you.  Take ^that as constructive criticism


Had you been actively following the thread when it was first started or you would have known that there were a lot of posts that got deleted by moderators due to content. There was definitely grounds for offence.

Reactions: Like 2


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## Travis K (Jul 26, 2011)

TexasTreeViper said:


> Had you been actively following the thread when it was first started or you would have known that there were a lot of posts that got deleted by moderators due to content. There was definitely grounds for offence.


If that is the case then I recant my previous post.

Reactions: Like 1


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## Comatose (Jul 26, 2011)

I'm going to check my M. balfouri when I get home... he/she is near a molt so perhaps I can help confirm/disprove this theory, or at least contribute to discussion.


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## Bosing (Jul 26, 2011)

If it would help, here are some pics of my M. balfouri.

Female









Male


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## xhexdx (Jul 27, 2011)

Confirmed by molt?


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## Bosing (Aug 8, 2011)

xhexdx said:


> Confirmed by molt?


More than exuvium, sir. The male inthe photo is with hooks already.  The female in the photo laid a sac thereafter but she decided to rearrange her enclosure a few days after, so it was a failed breeding attempt.


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## Anastasia (May 10, 2012)

I seriously have my doubts about this (pre adult) Sexual Dimorphism, I have several males and females aprox 3" +/- 
I didn't notice visual differences that I can point to, here is juvenile female (sexed confirmed)
http://www.net-bug.net/apps/photos/photo?photoid=155462813
I will post picture of male same size shortly,

   Anastasia.

---------- Post added 05-10-2012 at 12:02 PM ----------

this is male, they are siblings(with females above) and in very close molt schedules.


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## captmarga (May 10, 2012)

Just got a balfouri, sexed by molt as being female. She's about 2.75" DLS. 




Marga


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## Tonys spiders (May 10, 2012)

I can honestly say this is not true, because i have female thats around 5 inches and the blue extends slightly beyond her femurs just as much as a presumed pen ultimate male that i recently traded to Rich65. Both were sexed via molt. I beleieve coloration can differ from T to T. The method may work some of the time but if it doesnt work 100% of the time its not a good method to go by. Just my 2 cents.

Tony


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