Basically the title
Not sure if my pt murinus are slings yet.
Is it as soon as they lose the colourless appearance? Is the second nymph stage not as colourless?
They probably are spiderlings now, I just cant be sure when they turned.
As soon as they are mobile, or 1st or 2nd instar depending on the species. I have never heard of them being called nymphs :? . Technically, you could spiderlings now since 'spiderling' is not concrete on a particular developmental stage. There is no cut and dry way to do it since there is often a difference between different species in embryos, slings, and adults in regard to sizes.