Macaria grossbecki at Bentsen-Rio Grande Valley SP

On September 5, 2024, Bianca J. Banda (@biancajbanda) uploaded an observation of an unidentified Geometrid moth from Bentsen-Rio Grande Valley State Park. After wandering through the Moth Photographers' Group site and consulting Ferguson's 2008 MONA fascicle on the family, I identified the moth as Macaria [syn. Speranza] grossbecki, a very rare moth originally described in 1913 by Barnes & McDunnough from Brownsville and San Benito, Texas. Ferguson writes that "although [the species] was described from 19 specimens, few have since been collected". He had seen only two other specimens, one from Brownsville collected in 1928 and another from Santa Ana NWR in 1970. Here is Bianca's image of the species:

Bianca's image represents the First Known Photograph of a Living Specimen of the species.

The species can be recognized by the following combination of details:

-- Forewings whitish rather than gray, buff, or yellowish as in most other members of this subfamily.
-- Slightly wavy, nearly complete PM line which is heavily shaded on the inner 2/3, often showing two more prominent areas of thickening. A narrow AM line can be present or absent.
-- Two to four black subapical spots beyond the PM line. On Bianca's image, the right FW shows two such spots, one just below the subapical black mark on the costal margin and a smaller one at about the midway point and just beyond the shaded PM line. Images on MPG show 3 to 4 black spots lined up in this area.
-- A small black discal dot is usually present.
-- The fringe is mostly dark gray.

This species is most easily confused with the Frederickia cyda/s-signata complex, but those species have a much more sinuous (wavy) PM line, lack the subapical spots, usually lack a discal dot, and have a paler gray fringe that doesn't contrast with the ground color of the FW. Here are a few examples of this species complex:

Frederickia s-signata complex: (L) Falcon SP (Starr Co.); (mid) Balcones Canyonlands NWR (Travis Co.); (R) Timberlake Bio. Station (Mills Co.). All ph. by the author.

Thus far, the small set of records of Macaria grossbecki are confined to Cameron and Hidalgo Counties in the Lower Rio Grande Valley. I went through several hundred unidentified (and under-identified) Macariini across much of South Texas yesterday and found no other images of this species.

Congrats and many thanks to @biancajbanda for her efforts, attentiveness, and enthusiasm to document the wildlife of Bentsen-Rio Grande Valley SP!

Posted on 06 de setembro de 2024, 03:34 PM by gcwarbler