Ergaula pilosa, The Big Black Beetle Mimic Roaches
Welcome to another blog update, this time, for a discussion, regarding our hobby stock of Ergaula pilosa.
Invertebrate Dude already told us that Hobby "Ergaula pilosa" are NOT E.pilosa... so if you haven’t read his post yet, please do so now, as I will use it as a base for our conversation.
Hobby "Ergaula pilosa" are NOT E.pilosa...
As you know, I have recently found an Ergaula species in Thailand, which I pinned down to being Ergaula cf. silphoides, and which I wrote about on this post.
Ergaula cf. silphoides (Nakhon Ratchasima)
Few months have passed and I am pleased to tell you that some of my nymphs have matured, including a male and a female, which is fantastic. Furthermore, because I was using a regular substrate like coco-fiber and peat, the adults came out pretty clean from any debris, so we will be able to see their real coloration, as opposed to the adults I found in the wild, which were completely covered with clay, to a point where a wash under running water didn’t even help to remove it.
Running the risk of being redundant, but in order to avoid any mistakes, lets re-evaluate our wild caught species once again.
Cockroach Species File - Ergaula silphoides - limits the distribution of this species to Cambodia and Thailand. And I found my individuals right in the sweet spot. Thailand’s Nakhon Ratchasima province, which borders Cambodia, so it couldn’t be any more central to both areas.
Ergaula silphoides collection place
Cockroach Species File also indicates that the first citation for this species is located in Walker, F. 1868. Catalogue of the Specimens of Blattariae in the Collection of the British Museum 182 >> Polyphaga silphoides.
Thanks to Dr. George Beccaloni and his Taxonomic Works research papers collection, running a quick search, we are able to find the paper and go straight to its description.
Polyphaga silphoides description
After confirming the exact measurement of the scale shown in the photos above, each black bar corresponds to 1 mm.
So we are able to measure this adult female individual having an approximate length of 35mm. Our female measures 33mm.
Piceous - referring to a very dark brown
Broad, elliptical, convex
Dull
Pubescent, thickly and minutely punctured
Head black, shining, with a pale yellow band near the fore border - The yellow band is making reference to the set of yellow hairs near the fore border. Notice how all the other hairs are orange.
Eyes livid, wide apart -livid making a reference to the white markings surrounding the eyes.
….
Legs thick, shining, femora setose; tibiae with long stout spines
Fore wings coriaceous, extending somewhat beyond the abdomen ; costa rounded ; right wing with a furrow for the reception of the hind border of the left wing; covered part shining, semicoriaceous
Hind wings lurid, semi-coriaceous, not extending beyond the abdomen
As we can see, my female individual checks all of the above items in the description. So I am very extremely confident that it is indeed Ergaula silphoides.
So what does it have to do with Ergaula “pilosa” hobby stock?
Well, I think you must have noticed by now that my wild caught individuals are exactly the same as Ergaula “pilosa” hobby stock.
I have asked and searched online for some photos of “pilosa” hobby stock especially the head area, where the more distinctive features are located. And this is what I found.
Furthermore, I have also managed to find a good photo of Ergaula capucina head, just in case these features would be found in other Ergaula species, and it seems they were not, in this case.
As you can see, E.capucina doesn’t have the white marking surrounding the eyes.
As such, I am also now pretty sure that the Ergaula “pilosa” hobby stock is in fact Ergaula silphoides.
My theory is that someone collected Ergaula from Thailand or Cambodia, mislabelled it as Ergaula pilosa, probably due to the pilosity of the males or that central blotch which true pilosa also has. Then proceeded to pass down to other hobbyists without giving any information of the locality. Someone along the way, associated the Ergaula “pilosa” hobby stock coming from Borneo, because their distribution is limited to Malaysia and Borneo.
You can also find this mistake on iNaturalist, when you search for Ergaula genus in Thailand. Ergaula silphoides is never mentioned, you have either Ergaula capucina, Ergaula sp and Ergaula pilosa. Well Ergaula pilosa doesn’t occur in Thailand and what is happening is that people who have see Ergaula “pilosa” hobby stock are in fact mislabelling Ergaula silphoides as Ergaula pilosa.
To conclude your Big Black Beetle Mimic Roaches are Ergaula silphoides.