could someone explain the instar system to me?

[kosh]

i see people always talking about slings as being 2nd instar or 3rd instar etc....
can someone explain this system to me?
is every moult from birth considered some sort of instar? or is it just for babies??
when do you start referring to them as juveniles or sub-adults instead of 15th instar or something? :?

perhaps this is covered in the book i hope to buy from my other thread i just started.......

i hope you guys dont think i have too many topics going but, i have questions and what better place to have them answered?....plus sometimes i just wanna talk about Ts........so nnnyaahhhh!!!;P

 

[MrT]

I beleive that pretty much it Kosh. Each molt is a instar.

Please correct me if I'm wrong..

E

 

[Botar]

Yep, you guys have got it.

Botar

 

[Code Monkey]

Yep, the 1st instar is the "eggs with legs", 2nd instar when they become mobile, and each instar after that until they die is yet another instar. The other key ones is the penultimate instar (about to become sexually mature), ultimate instar (sexually mature), and post-ultimate instar (you figure it out ).

 

[kosh]

so, is there any science to the instar system in that..can you tell that a given T will become sexually mature by x instar?
and also...why then doesn't everyone refer to their spiders as x instar instead of sub-adult, adult, juvenile, sling, etc...seems like if everyone went by instar then when someone sold a T or referred to a T in a post or something more people might know exactly what they are talking about.....i imagine that "sub-adult", "juvenile", "adult" could cover several instars....as could an ad selling slings of various sizes 1/4", 1/2", 1".........
(maybe i just answered my own question......going by instars would be too much work when you could just say "juvenile" or "sub-adult" but, it sure seems like it would be more exact)

 

[Botar]

In addition to that, I have no idea how many molts most of my T's have been through prior to my acquisition. But if someone tells me they have a B. smithi sling, along with a size estimate, I have a rough idea of what they are talking about. The terms sling, juvenile, sub-adult, and adult, are all relative terms with no set definitions. I have an idea of the size of an adult A. geniculata, but couldn't tell you the size of a 10th instar A. geniculata.

Botar

 

[ArachnoJoost]

This is an 11th instar B. smithi
I bought it when it had 6 molts, all written down on the vial I bought it in. Don't know if the dates are accurate, but judging on the time inbetween I'd say pretty accurate.
Ohw yeah: edit: measured the euro up for you guys: it's just under one inch in diameter

 

[kosh]

well....i have written numbers on all the deli cups i got from Holley (1-10) and Holley was pretty sure they were second instar when she shipped them so i am going to say they are all now 3rd instar and i bought a little $0.77 notebook from Wal-Mart and i am keeping records of everything....so if and when they ever go to new owners ......they will come with a complete history....

 

[Botar]

Good move Kosh, I've done the same thing with my Holley slings. My group just started molting a couple of days ago. I'm glad everyone posts on their progress.

Botar

 

[Code Monkey]

Originally posted by kosh
so, is there any science to the instar system in that..can you tell that a given T will become sexually mature by x instar?
and also...why then doesn't everyone refer to their spiders as x instar instead of sub-adult, adult, juvenile, sling, etc...

Yes, there is some science to the idea, but with Ts it's a range. So, you could say that males of species Z typically mature on their 7th to 10th instar as an example.

But, like Botar says, how do you know what instar any particular T is? You've got dealers like Hoke and Swift caring for *thousands* of slings, you think they've got the time to pay attention to exactly how many times each of them have moulted? How about when you've got the little sling that spends 99.9% of its time in a burrow? Or when Joy feeds her Ts brontosaurus burgers and you're only feeding yours crickets so Joy's grow 2x as fast and mature four instars before yours?

A size is (or at least should be) an absolute. Saying a T is four inches or ten centimeters means the same thing regardless of species or who you're dealing with. Saying a T is on its sixth instar, even assuming that the designation is always accurate, means pretty much zip because you've then got to interpret what the sixth instar means for that species, inquire about how much/what the T has been fed on, temperature it was raised at, etc., etc. So much simpler and accurate to go by size - it's a pretty easy mental calculation to say if a female A. geniculata is seven to nine inches in leg span and you've got a four inch specimen it's immature. Now, how about if I told you I've got a ninth instar female A. geniculata, got any idea what I'm talking about or how big it is?

 

[kosh]

yeah i understand you perfectly CM..and it makes perfect sense.....but if there is science to it that x species would mature at x instar and this science were published somewhere (say in the T keepers guide) and everyone had learned that way from the start in the hobby then it would have made sense to someone if you said you had a 9th instar female A. geniculata........but i know that would probably me more than most people would care to have to learn and the hobby would probably suffer from it also........i was just curious though.......thanks for all the input....it is much appreciated.....i gotta order me some books so maybe i can quit clogging this corner of cyberspace with sometimes needless posts.....

also, CM, you mean that a given species doesnt always mature at a given instar?? you can speed up their maturity and moult frequency by powerfeeding, etc....this doesnt just increase size but also increases the physiological changes between moults?

 

[Joy]

Originally posted by Code Monkey
[BOr when Joy feeds her Ts brontosaurus burgers and you're only feeding yours crickets so Joy's grow 2x as fast and mature four instars before yours?

? [/B]

LOL First I am accused of feeding my spiders pork rinds, now brontosaurus burgers! It will be Kobe beef next, no doubt ;-)


As far as the instar system goes, my understanding (per Dr. R.G. Breene) is that the eggs eclode inside the eggsac, becoming post-embryos (eggs with legs, aka post-pulli), molt into 1st instars, then molt again into 2nd instars (in most species) before emerging from the eggsac.

Joy

 

[Code Monkey]

Originally posted by kosh
also, CM, you mean that a given species doesnt always mature at a given instar?? you can speed up their maturity and moult frequency by powerfeeding, etc....this doesnt just increase size but also increases the physiological changes between moults?

It's a more fixed rule with shorter lived inverts. I can't remember the name of the invert book I originally got this from (wasn't a T specific book), but the rule of thumb is that with most inverts you can even pinpoint the number of instars they have from hatching right up to death. Once you start stretching that lifespan from months to decades, though, the rules stop being so hard and fast. As a result, it becomes impossible to pin down exactly which instar maturity or death will occur because it's going to depend on other criteria beyond instar number.

Think about it like this: a tarantula is to normal spiders and arthropods like a redwood tree is to Kentucky fescue grass.
If you've raised a bunch of slings, you would see that the period between early moults is more or less fixed temporally but growth is dependent upon food availability. You don't want maturity 100% dependent upon instar number in a situation like this.