Narceus americanus or Narceus annularis?

[Exoskelos]

I have a bit of a suspicion that both species exist in my local area, and I think that the one I originally thought to be a morph, is most certainly N. annularis. It's too different, in both color and size. I just took probably my best photo of it, with some N. americanus I collected from VA last year. You'll notice its far thicker and darker than the others.
I don't think its a coincidence either, I found another one of similar size and coloration a month or two ago, along with smaller ones that had normal coloration. I doubt they were brood from the larger one, although it would support a theory I'm working on if they were. Of course the argument stands for not being able to differentiate on sight between the two.
Mainly, I wonder if these two species really need to be sent in for identification. This one I have is so wildly different than the others that either it is in fact N. annularis, or its the great grandmother of every Narceus millipede I've found around here, if colors darken with age and they continue to grow throughout their lifespan. It just boggles my mind how large it is. Its even wider than the N. gordanus adults.

 

[richard22]

If there is a difference, N. Annularis might be smaller. I caught a few in Jessup Maryland; marylandbiodiversity.com showed observations in Jessup for the annularis and not americanus. It’s all very confusing, but it seems N. Americanus and N. Annularis are all within the. Narceus-Americanus-Annularis-Complex, like they aren’t technically different species but maybe they have differences. I am a taxonomy amateur though, so I don’t know. I know the species is less toxic than most millipedes, like the greenhouse, because they only emit benzoquinones and not hydrogen cyanide.

 

[Elytra and Antenna]

They are two different species but the only absolute identification I know of is from male genitalia. Of course a new paper can split or combine any species and change the designation.