Just for comparison: this link
http://www.hotel-grille.de/IGM-Nummern.htm
leads to a list of stocks we are maintaining for about 2 years. As you see, many stocks disappear again very soon. There are mainly two reasons for this:
1. The species isn't appreciated very much and, consequently, only bred by a few people if not given up completely at all. If a species just occupies space that you can use for other species you are more interested in, and breeding this species isn't even appreciated by customers, why engaging in keeping it in the hobby?
2. The species is replaced by subsequently introduced species from the same genus. Most people don't (or are not able to) discriminate between the species of a genus and so the newer species, being rarer and more expensive at the beginning, will eventually replace its predecessor. As there are always the same people who introduce new species, they cannot breed all the species they introduce over the years, or: how many
Tarachodes or
Creobroter species can be bred by one person? So if they don't care, the former species is replaced by the latter. Of course one would think that spreading the species into the hobby is sufficient to ensure its persistance. This isn't the case.
In fact, I pointed out several times that many people aren't real, reliable breeders. Most persons get aggressive when confronted with this, but unfortunately, this is the truth. There are a few breeders and many "users" (in its very sense). So, maintaining a stock in culture (you see, I am talking about
stocks, not
species, as there may be more than one stock per species in culture) relies on just a few people only. If they quit this species it may well vanish soon.
Some words to the list: we try to name all stocks, but it is focused on European ones, as we don't get immediate input from overseas. Not every new stock gets a number, as it has to be spread first among the hobby in order to get one. Species which are difficult to raise and never get into the hobby get no number. So, only a few species really vanish because of problems with breeding them (as
Eremiaphila or
Phyllovates tripunctata). Most of them vanish because of logistic problems; or as I called it, "stochastic extinction".
Getting new species usually happens by either importing ooths or getting them by yourself. As the first possibility usually yiealds only suboptimal results (danger of fraud, and you mostly don't get what you want) we favor the second alternative. Most species from the list have a clear origin, that is, they were found in the habitat by ourselves.