I have heard that temperature influences the gender of baby tarantulas. I can't remember what the specs were, though. Whether or not the baby Ts are gender-less to start out, and acquire their gender through further development as influenced by temp (which I would tend to believe is true) or are engendered and then can have that gender altered by the temp (which I would tend not to believe) I don't know. Anyone know?
I do not know of any temperature sex correlation in ts. I do know, however, certian specie particularly prone to cannibalism will have a larger male turnout since males grow faster; this happens when breeders keep the spiders communally for the first few instars, allowing males to chow on their smaller sisters.
There is no temperature influence with Ts; their gender is chromosomally determined just like us. There was a good article in the ATS journal where someone decided to test this to verify/dispel the often repeated belief that temp influences gender.
The person reared several dozen Usambara slings at different temps and while development times were affected dramatically (at higher temps males would mature in as little as 9 months), the ratio was always about 50/50.
Some people have speculated that males might wind up being more common in a more Darwinian scenario because they are believed to grow faster initially and then out compete and out cannibalise their female siblings. This, however, is pure speculation at this point and its only relevance to the hobby is that, if true, it might influence the ratio available since some breeders will leave slings communually for a couple of moults to let the weak get weeded out (as well as make feeding them MUCH easier and quicker) before going to the time consuming process of separating them into individual containers. Again, though, speculation at this point.
Hopefully someone will get the wild idea of splitting a sizeable batch of spiderlings in half. One half gets separated into individual containers at the 2nd instar. The other batch gets reared communally until the 4th or so instar before being separated. Then, everybody gets reared until they become sexable and the data is passed out to us schmoes to put the question to rest.
Thank you for the correction. I had read the temp-gender correlation somewhere, likely on one of the lists, and since I have never reared baby Ts myself, took it to be true. It is good to know the reality of the situation.