1st Instar = 1st Moult after eggs with legs
2nd Instar = Second Moult, it becomes fully formed
3rd Instar= Is when the spider is fully formed and is able to be sold. If you get sold a 1st instar, the guy is either confused, or you basically bought a Egg with Legs that just moulted out.
We don't really use Instar for Tarantulas anyway, we rather use them for scorpions as Scorpions only moult 6 - 8 times their entire lives.
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