Orthogonioptilum arnoldi

Orthogonioptilum arnoldi
(Hering, 1932)

Orthogonioptilum arnoldi/neoprox/???, male, Ipassa Research Station, Ogooue-Ivindo, Gabon,
Novemver 2009, courtesy of Thibaud Decaens.

TAXONOMY:

Superfamily: Bombycoidea Latreille, 1802
Family: Saturniidae Boisduval, [1837] 1834
Subfamily: Micragoninae, Cockerell, 1914
Genus: Orthogonioptilum, Karsch, 1893

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"Moon River"
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The specimen depicted above was sent to me (Bill Oehlke) as Orthogonioptilum subueleense, and it may be that species. However, I think it is more likely O. arnoldi or O. neoprox which fly in the same area. The image I have of O. subueleense shows a much more produced forewing apex.

"I find it very difficult to determine identities of many of the Orthogoniptilum. In many cases there are several very similar species in the same habitat/location, and the generalized descriptions given in text references could apply to more than one species. The plates that I have available to me also are not of great quality, and it seems that specimens of this genus tend to fade rapidly in collections. My ability to read/translate French also is not great.

There may be much more obvious distinctions in fresh specimens or, even better, live moths.

The specimen from Ipassa Research Station has some features that suggest Orthogonioptilum neoprox, but it is hard to determine from photos if all characters are in order.

Philippe Darge describes neoprox as having a forewing anal angle that is greater than ninety degrees. In the live specimen, above, this angle seems less than ninety degrees, but the general distribution of colour, location and the small circular marking just below the costa at the juncture with the pm line are suggestive of neoprox.

I am more inclined to go with O. arnoldi, based primarily on subtle differences that suggest a better match for the image on Plate III in Darge's Saturniidae I. Philippe mentions, however, that the sightings for arnoldi in eastern Gabon are a bit problematic.

There are yet additional species (fang, etc.) that are very close, all reported from the same general area. Perhaps over time this will all get sorted out." Bill Oehlke

Of O. adustum, Philipppe Darge writes, "Refer to the card for O. bergeri Rougeot for the probable synonymity between the two species (adustum and bergeri)."

Darge describes O. bergeri as follows: The forewing is very falcate (much more so than in prox or neoprox), the hindwing is elongated (more than in uelense). The ground colour is a dark reddish brown. The fw pm line is well marked and rather thick. The transverse line is also well marked and especially thick on the lower wing. The am line is more subdued, especially near the costa.

There are two relatively large "points of light" on each wing, often accompanied by a third miniscule "point of light" on the hindwing.

O. subueleense is described as follows, courtesy of my translation from French to English.

"The forewing is quite falcate and is very drawn out.

The hindwing outer margin is a little less convex than in O. ueleense and O. bergeri (on the same wing, the postmedian line is a little closer to the outer margin than in the other two species).

The ground colour is a clear, beigey-brick, sometimes a little more reddish, but generally brighter than allied species."

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