Yeah, instar doesn't really correspond to size, but it does help inform how far along in development a sling is. For example, 2i is normally the first instar that will be available for sale or transfer because that's when they start feeding - before that, they're just too fragile and haven't fed themselves yet. Seems like 3i and 4i are the most common sling sizes available, and any further along than that are well started and (theoretically) not as challenging to raise. If you want to know the actual size, you'd need to contact the seller and ask.
I've been in the hobby nearly 6 years and it's still pretty useless tbh, a 7th instar P. langenbucheri is like 5cm leg span, an 8th instar A. bicoloratum is less than half that
That is exactly why this is a bad system, everyone seems to use it differently! So you acctually have to ask the seller how he/she was applying it.
I think the difference is mainly European vs American. Most American breeders/dealers/vendors go eggs, EWL, 1i, and then 2i. I believe Europeans use different designations. I think it's egg, N1, N2, and then L1. Once again, I think that's where the confusion comes from, where 2i is synonomous with L1 and people have a hard time with that mental conversion.
Well instars are a fairly simple concept in the arthropod world and so far i have seen nothing that would suggest that we should ignore the definition and treat the Prelarvae (EWL) as anything but 1i. I honestly do not understand why you wouldn't, maybe i am ignorant of some detail but i can't think of anything. If so please enlighten me, i am tired of worrying about this constantly.
I would love some clarification on it all as well, but ultimately I don't think we'll get it. That would require a global standardization of a naming convention for all hobbyists/breeders/dealers. For most, the drive isn't there and they don't keep track of instars past 2i. It's sort of become a binary, yes or no, true or false question where the goal is to just figure out if they're independent and eating yet or not. It's like turning 21 in the States and being able to buy alchohol. After that milestone, why even track age lol.
, despite double checking my books.
Not in the U.S.
www.britannica.com
No no I never said I was correct. I'm usually always wrong lol.
To my understanding, you both are right, @Wolfram1 and @Arachnophobphile. The "embryo -> larval stages -> nymphal stages -> adult" naming scheme works well for the fast growing araneomorphae where-as in the mygalomorphae there is no larval stage. Some researchers use the condensed naming scheme, or some variation, of "embryo -> post-embryo -> nymph -> adult" for the mygalomorphae, where the nymphal stages are all spiderling stages up to adult, because they have not fully developed, but even then that doesn't quite work. What makes mygale development naming and classification so tricky is what to call the period between post-embyro and adult when the adult, or ultimate instar, is not clear in females.