Check Thelacantha observations for "Gasteracantha mediofusca"

Hi all -- as originally pointed out by @michael-gasteracantha in a comment on the first observation linked below, there is a distinctive spiny orbweaver form currently listed as Gasteracantha mediofusca in the World Spider Catalog that may actually be conspecific with Thelacantha brevispina. It may also be a distinct species, but if so, it apparently belongs in Thelacantha, not Gasteracantha.

Here are four observations that match this form:

• https://www.inaturalist.org/observations/15616648
• https://www.inaturalist.org/observations/16248240
• https://www.inaturalist.org/observations/19754140
• https://www.inaturalist.org/observations/19879640

© 大肚魚, some rights reserved (CC-BY-NC)

The coloration is distinctive. Here is a description from Merian 1911 in original Dutch:

"Het midden-gedeelte van den rug van af den voorsten rand tot en met de achterste stekels donker zwartbruin, rnet twee witte lanwerpige vlekken in het midden, en cene dunne rozenroode streep tusschen beiden; de zijdeljike deelen wit, en aan het voorste gedeelte zeer fijn rozenrood gestreept."

And translated into English via Google Translate:

"The middle part of the back from the front edge to the rear spines of dark black-brown, with two white long spots in the middle, and a thin pink-red line between them; the side parts are white, and very fine rose-red at the front."

Until the taxonomy is revised (which may take several years), I think it makes sense to ID these individuals on iNaturalist as G. mediofusca, since that's how the taxon is currently handled in WSC. Perhaps keeping track of them here could even help solve the long-standing taxonomic mystery.

So as you review Thelacantha observations, keep an eye out for individuals matching mediofusca.

Oh, and until one or more of these observations gets to RG status, I can't figure out how to add any of these photos to the species overview page here on iNat, but hopefully we can do that soon to help build more awareness.

Posted on March 31, 2019 08:22 PM by djringer