It was known for a long time as P. perplexus, but in 2012 it was found that the older name P. rubiginosus actually referred to this species, before that the name P. rubiginosus was seen as a synonym of P. carolina. P. perplexus was named in 1872 for six specimens collected in Texas by Ezra Townsend Cresson and Matthias Buck et al. ). Cresson himself does not mention P. carolina, but states that he found P. perplexus very closely resembling P. rubiginosus, also recognised as a species in his time, and perhaps just to be a male form of this taxon. He also described P. generosus as a new species in the same paper, from three specimens from Texas, stating that it "may be an extreme variety of perplexus". P. generosus was published on the next page after P. perplexus, which means that when the two taxa were considered synonym, P. perplexus had taxonomic priority because it was published first. Owain Richards saw it as a synonym of P. carolina in 1978, although Wade and Nelson recognised it as a species in a paper published the same year. Thus the taxon was for a long time, and until relatively recently, confused with P. carolina.
Description
The length of the forewing is 18.0–21.5 mm in the female, 17.0–18.0 mm in the male. The body of the creature is almost entirely rusty red, broken by a number of black to dark brown markings. These markings consist of a usually well developed spot around the eyes, this rarely divided into individual spots around each eye, and often a spot in front of pronotalcarina. In some cases there are yellow markings on the propodeal valves and tarsi. Polistes rubiginosus and P. carolina are the only large red-coloured wasp species in the eastern US. P. rubiginosus is, however, extremely similar to P. carolina, and can be found in the same regions; the key morphological difference being the malar area seen from the side, but this works only for the female wasps. This area and the gena are covered in silvery pubescent hairs. P. rubiginosus is the only Polistes wasp in the P. fuscatus-group to have this characteristic, all other species have this area bare or almost so. Both sexes of P. perplexus can also be distinguished from P. carolina by the coarser transverse ridging of the propodeum.
Distribution
This species appears to be an endemic of the US. In 1979 Krombein states P. perplexus occurred from Maryland south to Georgia and from there west to southern Illinois, Kansas, Oklahoma and Texas. As of 2020 it has been recorded in the states of Arizona, Arkansas, Florida, Illinois, Kentucky, Louisiana, Missouri, Ohio, Oklahoma, Pennsylvania and Texas. The modern known distribution thus exceeds that given in Krombein in all directions because of problems with identification. The species very similar to P. carolina and may have been under-reported. The specimen from Arizona was collected in 1923 but only properly identified in 2016. The first records from Florida date to 1989. The record from Pennsylvania is from 2005. The distribution largely overlaps with that of P. carolina.
Ecology
The ecology is poorly known because of the aforementioned confusion with P. carolina. It is an eusocial insect, building nests in sheltered locations such as in hollow trees, or under wooden platforms and inside storage buildings. Adults have been seen feeding on Euthamia graminifolia and/or E. caroliniana in Florida.
