Martin Oosthuysen wrote: Hello
Usually when they are going into pre-molt, their abdomens will go dark. ..
You're on the right track, but you're not giving enough information to be useful. Tarantulas are
NOT that simple.
The majority, but not all New World tarantulas possess a patch of special bristles on the top, rear of their abdomens. These bristles are called urticating bristles because they cause an itchy rash, otherwise known as an
urticaria
.
Every time one of these tarantulas molts it automatically replaces all its bristles, including any shed urticating bristles. Between molts these bristles are gradually lost by merely falling off. Occasionally, the tarantula may rub them off in large masses and fluff them into the air as a defense reaction. This will eventually leave a bear spot (a.k.a., "bald patch"). Because the exoskeleton on a tarantula's rump is so thin it's very nearly transparent, and the resulting bear spot appears to be sort of tannish colored.
As the tarantula prepares to molt it grows a new exoskeleton complete with a new set of bristles immediately inside the old exoskeleton. And as those new bristles "mature" and develop their final coloring, the bare spot turns dark, almost always to a nearly jet black color.
Thus, if you have one of the New World tarantulas that possess urticating bristles on their rumps, you can tell when it's preparing to molt by watching the color of the resulting bald spot.
Because not all New World tarantulas possess urticating bristles in this area, this rule is not universal for all New World tarantulas.
And, as of this writing, no Old World tarantulas are known to possess urticating bristles, so it doesn't work for any of them.
Lastly, to keep this dissertation to a manageable length I have glossed over or ignored some of the details of the molting process. Before you quote the details of molting presented here you should read Foelix' book,
Biology of Spiders
.
Pop quizzes daily, your little 8-legged Yoda will be giving you!
