Fotos / Sonidos

Observ.

bradmoon

Fecha

Junio 11, 2020 03:21 PM CDT

Descripción

Male and female Promachus quadratus. In the photos here, the P. quadratus are for this observation. The comparison photos of P. bastardii (on the right side of each comparison) are from other observations farther inland in Louisiana (https://www.inaturalist.org/observations/18569834, https://www.inaturalist.org/observations/19356761, and https://www.inaturalist.org/observations/51155008).

Promachus quadratus and P. bastardii are challenging to distinguish from one another. Hine (1911) studied specimens of P. quadratus from this area (Cameron Parish, Louisiana) and noted that they can be distinguished from P. bastardii by the overall lighter color (vs. darker brown in P. bastardii), smaller black area on top of each abdominal segment and larger light posterior margin of each segment (vs. larger dark areas and smaller light areas in P. bastardii), mostly yellow hairs on the palpi adjacent to proboscis (vs. black hairs in P. bastardii), and wings that are clearer (vs. browner in P. bastardii) with gray shading in the first submarginal cell that is much narrower than the cell (distinct gray shadow up to about 1/4 as wide as the cell vs. gray shadow that is about 1/2 as wide as the cell at the widest part in P. bastardii). Dave Patton also showed this narrow submarginal shading close-up in specimens from the same area as this observation (see https://bugguide.net/node/view/1692599 and https://bugguide.net/node/view/1692608). The darker color of P. bastardii also makes the long light hairs at the posterior margin of each abdominal segment stand out in higher contrast to the background color, whereas in P. quadratus there is much less contrast in those colors.

Bromley (1934) named the essentially identical robber flies in east Texas as a distinct species, Promachus texanus, and noted that they were often identified as P. quadratus. He also called into question whether P. quadratus was truly distinct from P. bastardii, but without pointing to any features or providing any evidence or citations to support that statement. As far as I can tell from the original descriptions as well as Hine's 1911 study, Bromley (1934) only described one subtle feature that differed between P. texanus and P. quadratus, which was that the halteres are black in P. texanus (vs. brown in P. quadratus according to the original description by Weidemann, 1828). So, unless I'm missing something in the literature (always a possibility because I'm not an expert in robber flies or taxonomy!), it appears to me that P. texanus isn't distinct from P. quadratus, and therefore that the name Promachus quadratus should have priority over Promachus texanus, at least until additional evidence is published demonstrating that P. texanus is in fact distinct from P. quadratus.

These photos also show other differences between P. quadratus and P. bastardii, such as light hairs with dark bristles on the posterior scutum and scutellum, light proximal and distal metatarsi with dark in between on the middle leg, light outer tibia on the hind leg, and light hairs under the abdomen in P. quadratus (vs. all darker in P. bastardii). Hine didn't mention these differences, and I haven't seen enough specimens to know if they are consistent or variable.

Fotos / Sonidos

Square

Observ.

giffbeaton

Fecha

Mayo 15, 2019 09:23 AM EDT

Descripción

On the outside of a Gopher Tortoise burrow

Fotos / Sonidos

Square

Observ.

patrich

Fecha

Enero 1, 2018