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Nicolas Rousseaux

Gromphadorhina and Princisia, taxonomic discussion

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Hi

we were just talking about the genus Gromphadorhina and Princisia with Orin on an other topic, and we were talking about their identification wich is difficult, and most of the time incertain.

I think that a discussion about this would be really interesting on the forum, so that everyone can access the informations on this subject.

Well, the discussion has started like this:

me:

"But beware, loads of hissers are actually hybrids or misindentified. I bought 3 different species last years, and give a male of each one to a friend of mine. He compared the genitalia with the schema of a scientific book and all the species were misidentified ;)"

Orin:

"Gromphadorhina descriptions were based primarily on the horn structure of the male, I've seen some of the original descriptions. I'd love to see that schema of hisser genitalia in a scan. Original descriptions based on variable horn structure, pronotum shape and surface texture is why stocks I sent specimens of to a cockroach taxonomist identified as G. portentosa, G. oblongonota, and Princisia all interbreed readily in captivity. They probably are just geographic races and may not even qualify as different subspecies. It is not that people misidentify them, the original "Princisia" never existed and was simply a taxonomic error of someone trying to use a variable specific character as though it were a stable generic character (the notch in the pronotum) without checking to see the male genitalia were identical. However, this does not mean there are not a number of unique stocks that vary in appearance and specific husbandry."

So, to continue this conversation, here is the scan:

post-3063-0-71567300-1357304484_thumb.jpg

(sorry, he lend the book to someone and we can't remember wich species the genitalias refer to)

It's from one of those books:

• Herrewege C. van, 1973a – Contribution

à l'étude des Blattaria de la faune malgache : I. Princisia, gen. nov., voisin de

Gromphadorhina Brunner v. W., description d'une espèce nouvelle – Bulletin de la

Société Linnéenne de Lyon.

• Herrewege C. van, 1973b - Contribution

à l'étude des Blattaria de la faune malgache : II. Description de huit espèces

nouvelles appartenant aux genres

Gromphadorhina Brunner v. W. et

Elliptorhina gen. nov. – Bulletin de la

Société Linnéenne de Lyon.

According to the books, the pronotum isn't totally reliable: you can find different forms and sizes in a same population.

The best way to identify them is the analysis of the genitalia, there are little differences... But they exists.

In my opinion, in one hand, we should wait for the revision of those genus, and in a second hand, we should wait for the developement of genetics analysis and compare our hissers to the genetic code of wild hissers. This method is more and more used to identify diptera, we can hope to identify some hissers with this one day, and breed pure Gromphadorhina in captivity!

You're probably right Orin, when you say Princisia is just a Gromphadorhina form. And I think that Gromphadorhina portentosa, Gromphadorhina grandidieri, Gromphadorhina oblongonata and Gromphadorhina picea are maybe four subspecies of a same specie, or maybe just geographic forms. There are already some forms known (some colours are related to particular area, other are just selection in bred).

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There is always the possibility that our captive P. vanwaerebeki stock actually isn't P. vanwaerebeki. As I recall until very recently two species of Balta were traded under the name "Onchyostylus" which apparently isn't a genus of anything.

But operating under the assumption that our Princisia are indeed "Princisia"...

Due to their aptery these roaches have very low dispersal in the wild. This leads to increased differentiation in isolated populations. One population of hissers in a log several meters from another may be kept separate by a river, a pond, an open space, or any of a number of other factors, meaning they could rapidly deviate from eachother in a short amount of time. There could be hundreds of these scenarios going on across Madagascar with subsequent hundreds of hisser varieties involved. Whether or not they can hybridize is something that only captivity might test.

Now, following this logic, I'd be inclined to say they're separate species. But roach taxonomy has never been that easy; Blaberus craniifer and its various "color morphs" are staunchly supported by some as just that: color morphs. But from what I have read B. craniifer (the black-winged species) was originally separated from the other species (we'll use the nomen nudum B. fusca here as well the potentially legitimate taxon B. peruvianus to represent the brown-winged species) by vicarience, which would mean that these varieties which are constantly purported to be the same are as different (using the argument that propagates the establishment of the hissers as separate species) as the hisser species. This all, of course, disregards the actions of humans, who (from much personal experience) have introduced many roach species to many places they do not naturally occur (and currently there ARE hundreds of roach species proliferating in locales across the globe, understudied and completely unknown to humans because they are "just cockroaches") and may alter the "practicality" of a statement which accounts for things in an "undisturbed" state of being.

It's a lot of politics and quite frankly it's not a pressing issue, though I believe there was work done at Imperial College in London on Blaberus species (using European lineages which may or may not be hybrids but assuming they weren't) which is currently looking into Blaberus sp. relations.

I would like to also say, while I'm still riled up about roach taxonomy, that the infamous argument for the B. craniifer holotype "having brown wings" is incorrect. The holotype for B. craniifer is a nymph; immature and therefore not possessing any wings whatsoever.

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P. vanwaerebeki and G. oblongonata Can hybridize I've seen them sold. To be honest the offspring are stunning coloring and large which is probably how the Big P. vanwaerebeki came to be in the first place perhaps. They are very docile too and don't hiss as much so make great pets my cousins had one it lived about 4 years it was female.

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There is always the possibility that our captive P. vanwaerebeki stock actually isn't P. vanwaerebeki.

I mentioned in another thread I sent Princisia and our G. portentosa, and G. oblongonota specimens to a taxonomist who positively identified them. I had originally considered we just had different variations of G. portentosa labeled incorrectly instead of variations of G. portentosa described incorrectly.

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I have some information that George Beccaloni wants to do detailed revision of tribe Gromphadorhini but it will not be in the near time.

BTW: Gromphadorhina grandidieri in captivity in the USA is not Gromphadorhina grandidieri!

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